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@@ -33,3 +33,4 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 *.zip filter=lfs diff=lfs merge=lfs -text
 *.zst filter=lfs diff=lfs merge=lfs -text
 *tfevents* filter=lfs diff=lfs merge=lfs -text
+detectron2/_C.cpython-39-x86_64-linux-gnu.so filter=lfs diff=lfs merge=lfs -text

detectron2/_C.cpython-39-x86_64-linux-gnu.so

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:352385592367aed0ff324539db0bc25b81bb743b2c3315acfb54326a072553cc
+size 1509208

detectron2/__init__.py

@@ -0,0 +1,10 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+from .utils.env import setup_environment
+
+setup_environment()
+
+
+# This line will be programatically read/write by setup.py.
+# Leave them at the bottom of this file and don't touch them.
+__version__ = "0.6"

detectron2/checkpoint/__init__.py

@@ -0,0 +1,10 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+# File:
+
+
+from . import catalog as _UNUSED  # register the handler
+from .detection_checkpoint import DetectionCheckpointer
+from fvcore.common.checkpoint import Checkpointer, PeriodicCheckpointer
+
+__all__ = ["Checkpointer", "PeriodicCheckpointer", "DetectionCheckpointer"]

detectron2/checkpoint/c2_model_loading.py

@@ -0,0 +1,406 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import copy
+import logging
+import re
+from typing import Dict, List
+import torch
+
+
+def convert_basic_c2_names(original_keys):
+    """
+    Apply some basic name conversion to names in C2 weights.
+    It only deals with typical backbone models.
+
+    Args:
+        original_keys (list[str]):
+    Returns:
+        list[str]: The same number of strings matching those in original_keys.
+    """
+    layer_keys = copy.deepcopy(original_keys)
+    layer_keys = [
+        {"pred_b": "linear_b", "pred_w": "linear_w"}.get(k, k) for k in layer_keys
+    ]  # some hard-coded mappings
+
+    layer_keys = [k.replace("_", ".") for k in layer_keys]
+    layer_keys = [re.sub("\\.b$", ".bias", k) for k in layer_keys]
+    layer_keys = [re.sub("\\.w$", ".weight", k) for k in layer_keys]
+    # Uniform both bn and gn names to "norm"
+    layer_keys = [re.sub("bn\\.s$", "norm.weight", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.bias$", "norm.bias", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.rm", "norm.running_mean", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.running.mean$", "norm.running_mean", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.riv$", "norm.running_var", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.running.var$", "norm.running_var", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.gamma$", "norm.weight", k) for k in layer_keys]
+    layer_keys = [re.sub("bn\\.beta$", "norm.bias", k) for k in layer_keys]
+    layer_keys = [re.sub("gn\\.s$", "norm.weight", k) for k in layer_keys]
+    layer_keys = [re.sub("gn\\.bias$", "norm.bias", k) for k in layer_keys]
+
+    # stem
+    layer_keys = [re.sub("^res\\.conv1\\.norm\\.", "conv1.norm.", k) for k in layer_keys]
+    # to avoid mis-matching with "conv1" in other components (e.g. detection head)
+    layer_keys = [re.sub("^conv1\\.", "stem.conv1.", k) for k in layer_keys]
+
+    # layer1-4 is used by torchvision, however we follow the C2 naming strategy (res2-5)
+    # layer_keys = [re.sub("^res2.", "layer1.", k) for k in layer_keys]
+    # layer_keys = [re.sub("^res3.", "layer2.", k) for k in layer_keys]
+    # layer_keys = [re.sub("^res4.", "layer3.", k) for k in layer_keys]
+    # layer_keys = [re.sub("^res5.", "layer4.", k) for k in layer_keys]
+
+    # blocks
+    layer_keys = [k.replace(".branch1.", ".shortcut.") for k in layer_keys]
+    layer_keys = [k.replace(".branch2a.", ".conv1.") for k in layer_keys]
+    layer_keys = [k.replace(".branch2b.", ".conv2.") for k in layer_keys]
+    layer_keys = [k.replace(".branch2c.", ".conv3.") for k in layer_keys]
+
+    # DensePose substitutions
+    layer_keys = [re.sub("^body.conv.fcn", "body_conv_fcn", k) for k in layer_keys]
+    layer_keys = [k.replace("AnnIndex.lowres", "ann_index_lowres") for k in layer_keys]
+    layer_keys = [k.replace("Index.UV.lowres", "index_uv_lowres") for k in layer_keys]
+    layer_keys = [k.replace("U.lowres", "u_lowres") for k in layer_keys]
+    layer_keys = [k.replace("V.lowres", "v_lowres") for k in layer_keys]
+    return layer_keys
+
+
+def convert_c2_detectron_names(weights):
+    """
+    Map Caffe2 Detectron weight names to Detectron2 names.
+
+    Args:
+        weights (dict): name -> tensor
+
+    Returns:
+        dict: detectron2 names -> tensor
+        dict: detectron2 names -> C2 names
+    """
+    logger = logging.getLogger(__name__)
+    logger.info("Renaming Caffe2 weights ......")
+    original_keys = sorted(weights.keys())
+    layer_keys = copy.deepcopy(original_keys)
+
+    layer_keys = convert_basic_c2_names(layer_keys)
+
+    # --------------------------------------------------------------------------
+    # RPN hidden representation conv
+    # --------------------------------------------------------------------------
+    # FPN case
+    # In the C2 model, the RPN hidden layer conv is defined for FPN level 2 and then
+    # shared for all other levels, hence the appearance of "fpn2"
+    layer_keys = [
+        k.replace("conv.rpn.fpn2", "proposal_generator.rpn_head.conv") for k in layer_keys
+    ]
+    # Non-FPN case
+    layer_keys = [k.replace("conv.rpn", "proposal_generator.rpn_head.conv") for k in layer_keys]
+
+    # --------------------------------------------------------------------------
+    # RPN box transformation conv
+    # --------------------------------------------------------------------------
+    # FPN case (see note above about "fpn2")
+    layer_keys = [
+        k.replace("rpn.bbox.pred.fpn2", "proposal_generator.rpn_head.anchor_deltas")
+        for k in layer_keys
+    ]
+    layer_keys = [
+        k.replace("rpn.cls.logits.fpn2", "proposal_generator.rpn_head.objectness_logits")
+        for k in layer_keys
+    ]
+    # Non-FPN case
+    layer_keys = [
+        k.replace("rpn.bbox.pred", "proposal_generator.rpn_head.anchor_deltas") for k in layer_keys
+    ]
+    layer_keys = [
+        k.replace("rpn.cls.logits", "proposal_generator.rpn_head.objectness_logits")
+        for k in layer_keys
+    ]
+
+    # --------------------------------------------------------------------------
+    # Fast R-CNN box head
+    # --------------------------------------------------------------------------
+    layer_keys = [re.sub("^bbox\\.pred", "bbox_pred", k) for k in layer_keys]
+    layer_keys = [re.sub("^cls\\.score", "cls_score", k) for k in layer_keys]
+    layer_keys = [re.sub("^fc6\\.", "box_head.fc1.", k) for k in layer_keys]
+    layer_keys = [re.sub("^fc7\\.", "box_head.fc2.", k) for k in layer_keys]
+    # 4conv1fc head tensor names: head_conv1_w, head_conv1_gn_s
+    layer_keys = [re.sub("^head\\.conv", "box_head.conv", k) for k in layer_keys]
+
+    # --------------------------------------------------------------------------
+    # FPN lateral and output convolutions
+    # --------------------------------------------------------------------------
+    def fpn_map(name):
+        """
+        Look for keys with the following patterns:
+        1) Starts with "fpn.inner."
+           Example: "fpn.inner.res2.2.sum.lateral.weight"
+           Meaning: These are lateral pathway convolutions
+        2) Starts with "fpn.res"
+           Example: "fpn.res2.2.sum.weight"
+           Meaning: These are FPN output convolutions
+        """
+        splits = name.split(".")
+        norm = ".norm" if "norm" in splits else ""
+        if name.startswith("fpn.inner."):
+            # splits example: ['fpn', 'inner', 'res2', '2', 'sum', 'lateral', 'weight']
+            stage = int(splits[2][len("res") :])
+            return "fpn_lateral{}{}.{}".format(stage, norm, splits[-1])
+        elif name.startswith("fpn.res"):
+            # splits example: ['fpn', 'res2', '2', 'sum', 'weight']
+            stage = int(splits[1][len("res") :])
+            return "fpn_output{}{}.{}".format(stage, norm, splits[-1])
+        return name
+
+    layer_keys = [fpn_map(k) for k in layer_keys]
+
+    # --------------------------------------------------------------------------
+    # Mask R-CNN mask head
+    # --------------------------------------------------------------------------
+    # roi_heads.StandardROIHeads case
+    layer_keys = [k.replace(".[mask].fcn", "mask_head.mask_fcn") for k in layer_keys]
+    layer_keys = [re.sub("^\\.mask\\.fcn", "mask_head.mask_fcn", k) for k in layer_keys]
+    layer_keys = [k.replace("mask.fcn.logits", "mask_head.predictor") for k in layer_keys]
+    # roi_heads.Res5ROIHeads case
+    layer_keys = [k.replace("conv5.mask", "mask_head.deconv") for k in layer_keys]
+
+    # --------------------------------------------------------------------------
+    # Keypoint R-CNN head
+    # --------------------------------------------------------------------------
+    # interestingly, the keypoint head convs have blob names that are simply "conv_fcnX"
+    layer_keys = [k.replace("conv.fcn", "roi_heads.keypoint_head.conv_fcn") for k in layer_keys]
+    layer_keys = [
+        k.replace("kps.score.lowres", "roi_heads.keypoint_head.score_lowres") for k in layer_keys
+    ]
+    layer_keys = [k.replace("kps.score.", "roi_heads.keypoint_head.score.") for k in layer_keys]
+
+    # --------------------------------------------------------------------------
+    # Done with replacements
+    # --------------------------------------------------------------------------
+    assert len(set(layer_keys)) == len(layer_keys)
+    assert len(original_keys) == len(layer_keys)
+
+    new_weights = {}
+    new_keys_to_original_keys = {}
+    for orig, renamed in zip(original_keys, layer_keys):
+        new_keys_to_original_keys[renamed] = orig
+        if renamed.startswith("bbox_pred.") or renamed.startswith("mask_head.predictor."):
+            # remove the meaningless prediction weight for background class
+            new_start_idx = 4 if renamed.startswith("bbox_pred.") else 1
+            new_weights[renamed] = weights[orig][new_start_idx:]
+            logger.info(
+                "Remove prediction weight for background class in {}. The shape changes from "
+                "{} to {}.".format(
+                    renamed, tuple(weights[orig].shape), tuple(new_weights[renamed].shape)
+                )
+            )
+        elif renamed.startswith("cls_score."):
+            # move weights of bg class from original index 0 to last index
+            logger.info(
+                "Move classification weights for background class in {} from index 0 to "
+                "index {}.".format(renamed, weights[orig].shape[0] - 1)
+            )
+            new_weights[renamed] = torch.cat([weights[orig][1:], weights[orig][:1]])
+        else:
+            new_weights[renamed] = weights[orig]
+
+    return new_weights, new_keys_to_original_keys
+
+
+# Note the current matching is not symmetric.
+# it assumes model_state_dict will have longer names.
+def align_and_update_state_dicts(model_state_dict, ckpt_state_dict, c2_conversion=True):
+    """
+    Match names between the two state-dict, and returns a new chkpt_state_dict with names
+    converted to match model_state_dict with heuristics. The returned dict can be later
+    loaded with fvcore checkpointer.
+    If `c2_conversion==True`, `ckpt_state_dict` is assumed to be a Caffe2
+    model and will be renamed at first.
+
+    Strategy: suppose that the models that we will create will have prefixes appended
+    to each of its keys, for example due to an extra level of nesting that the original
+    pre-trained weights from ImageNet won't contain. For example, model.state_dict()
+    might return backbone[0].body.res2.conv1.weight, while the pre-trained model contains
+    res2.conv1.weight. We thus want to match both parameters together.
+    For that, we look for each model weight, look among all loaded keys if there is one
+    that is a suffix of the current weight name, and use it if that's the case.
+    If multiple matches exist, take the one with longest size
+    of the corresponding name. For example, for the same model as before, the pretrained
+    weight file can contain both res2.conv1.weight, as well as conv1.weight. In this case,
+    we want to match backbone[0].body.conv1.weight to conv1.weight, and
+    backbone[0].body.res2.conv1.weight to res2.conv1.weight.
+    """
+    model_keys = sorted(model_state_dict.keys())
+    if c2_conversion:
+        ckpt_state_dict, original_keys = convert_c2_detectron_names(ckpt_state_dict)
+        # original_keys: the name in the original dict (before renaming)
+    else:
+        original_keys = {x: x for x in ckpt_state_dict.keys()}
+    ckpt_keys = sorted(ckpt_state_dict.keys())
+
+    def match(a, b):
+        # Matched ckpt_key should be a complete (starts with '.') suffix.
+        # For example, roi_heads.mesh_head.whatever_conv1 does not match conv1,
+        # but matches whatever_conv1 or mesh_head.whatever_conv1.
+        return a == b or a.endswith("." + b)
+
+    # get a matrix of string matches, where each (i, j) entry correspond to the size of the
+    # ckpt_key string, if it matches
+    match_matrix = [len(j) if match(i, j) else 0 for i in model_keys for j in ckpt_keys]
+    match_matrix = torch.as_tensor(match_matrix).view(len(model_keys), len(ckpt_keys))
+    # use the matched one with longest size in case of multiple matches
+    max_match_size, idxs = match_matrix.max(1)
+    # remove indices that correspond to no-match
+    idxs[max_match_size == 0] = -1
+
+    logger = logging.getLogger(__name__)
+    # matched_pairs (matched checkpoint key --> matched model key)
+    matched_keys = {}
+    result_state_dict = {}
+    for idx_model, idx_ckpt in enumerate(idxs.tolist()):
+        if idx_ckpt == -1:
+            continue
+        key_model = model_keys[idx_model]
+        key_ckpt = ckpt_keys[idx_ckpt]
+        value_ckpt = ckpt_state_dict[key_ckpt]
+        shape_in_model = model_state_dict[key_model].shape
+
+        if shape_in_model != value_ckpt.shape:
+            logger.warning(
+                "Shape of {} in checkpoint is {}, while shape of {} in model is {}.".format(
+                    key_ckpt, value_ckpt.shape, key_model, shape_in_model
+                )
+            )
+            logger.warning(
+                "{} will not be loaded. Please double check and see if this is desired.".format(
+                    key_ckpt
+                )
+            )
+            continue
+
+        assert key_model not in result_state_dict
+        result_state_dict[key_model] = value_ckpt
+        if key_ckpt in matched_keys:  # already added to matched_keys
+            logger.error(
+                "Ambiguity found for {} in checkpoint!"
+                "It matches at least two keys in the model ({} and {}).".format(
+                    key_ckpt, key_model, matched_keys[key_ckpt]
+                )
+            )
+            raise ValueError("Cannot match one checkpoint key to multiple keys in the model.")
+
+        matched_keys[key_ckpt] = key_model
+
+    # logging:
+    matched_model_keys = sorted(matched_keys.values())
+    if len(matched_model_keys) == 0:
+        logger.warning("No weights in checkpoint matched with model.")
+        return ckpt_state_dict
+    common_prefix = _longest_common_prefix(matched_model_keys)
+    rev_matched_keys = {v: k for k, v in matched_keys.items()}
+    original_keys = {k: original_keys[rev_matched_keys[k]] for k in matched_model_keys}
+
+    model_key_groups = _group_keys_by_module(matched_model_keys, original_keys)
+    table = []
+    memo = set()
+    for key_model in matched_model_keys:
+        if key_model in memo:
+            continue
+        if key_model in model_key_groups:
+            group = model_key_groups[key_model]
+            memo |= set(group)
+            shapes = [tuple(model_state_dict[k].shape) for k in group]
+            table.append(
+                (
+                    _longest_common_prefix([k[len(common_prefix) :] for k in group]) + "*",
+                    _group_str([original_keys[k] for k in group]),
+                    " ".join([str(x).replace(" ", "") for x in shapes]),
+                )
+            )
+        else:
+            key_checkpoint = original_keys[key_model]
+            shape = str(tuple(model_state_dict[key_model].shape))
+            table.append((key_model[len(common_prefix) :], key_checkpoint, shape))
+    submodule_str = common_prefix[:-1] if common_prefix else "model"
+    logger.info(
+        f"Following weights matched with submodule {submodule_str} - Total num: {len(table)}"
+    )
+
+    unmatched_ckpt_keys = [k for k in ckpt_keys if k not in set(matched_keys.keys())]
+    for k in unmatched_ckpt_keys:
+        result_state_dict[k] = ckpt_state_dict[k]
+    return result_state_dict
+
+
+def _group_keys_by_module(keys: List[str], original_names: Dict[str, str]):
+    """
+    Params in the same submodule are grouped together.
+
+    Args:
+        keys: names of all parameters
+        original_names: mapping from parameter name to their name in the checkpoint
+
+    Returns:
+        dict[name -> all other names in the same group]
+    """
+
+    def _submodule_name(key):
+        pos = key.rfind(".")
+        if pos < 0:
+            return None
+        prefix = key[: pos + 1]
+        return prefix
+
+    all_submodules = [_submodule_name(k) for k in keys]
+    all_submodules = [x for x in all_submodules if x]
+    all_submodules = sorted(all_submodules, key=len)
+
+    ret = {}
+    for prefix in all_submodules:
+        group = [k for k in keys if k.startswith(prefix)]
+        if len(group) <= 1:
+            continue
+        original_name_lcp = _longest_common_prefix_str([original_names[k] for k in group])
+        if len(original_name_lcp) == 0:
+            # don't group weights if original names don't share prefix
+            continue
+
+        for k in group:
+            if k in ret:
+                continue
+            ret[k] = group
+    return ret
+
+
+def _longest_common_prefix(names: List[str]) -> str:
+    """
+    ["abc.zfg", "abc.zef"] -> "abc."
+    """
+    names = [n.split(".") for n in names]
+    m1, m2 = min(names), max(names)
+    ret = [a for a, b in zip(m1, m2) if a == b]
+    ret = ".".join(ret) + "." if len(ret) else ""
+    return ret
+
+
+def _longest_common_prefix_str(names: List[str]) -> str:
+    m1, m2 = min(names), max(names)
+    lcp = []
+    for a, b in zip(m1, m2):
+        if a == b:
+            lcp.append(a)
+        else:
+            break
+    lcp = "".join(lcp)
+    return lcp
+
+
+def _group_str(names: List[str]) -> str:
+    """
+    Turn "common1", "common2", "common3" into "common{1,2,3}"
+    """
+    lcp = _longest_common_prefix_str(names)
+    rest = [x[len(lcp) :] for x in names]
+    rest = "{" + ",".join(rest) + "}"
+    ret = lcp + rest
+
+    # add some simplification for BN specifically
+    ret = ret.replace("bn_{beta,running_mean,running_var,gamma}", "bn_*")
+    ret = ret.replace("bn_beta,bn_running_mean,bn_running_var,bn_gamma", "bn_*")
+    return ret

detectron2/checkpoint/catalog.py

@@ -0,0 +1,115 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import logging
+
+from detectron2.utils.file_io import PathHandler, PathManager
+
+
+class ModelCatalog:
+    """
+    Store mappings from names to third-party models.
+    """
+
+    S3_C2_DETECTRON_PREFIX = "https://dl.fbaipublicfiles.com/detectron"
+
+    # MSRA models have STRIDE_IN_1X1=True. False otherwise.
+    # NOTE: all BN models here have fused BN into an affine layer.
+    # As a result, you should only load them to a model with "FrozenBN".
+    # Loading them to a model with regular BN or SyncBN is wrong.
+    # Even when loaded to FrozenBN, it is still different from affine by an epsilon,
+    # which should be negligible for training.
+    # NOTE: all models here uses PIXEL_STD=[1,1,1]
+    # NOTE: Most of the BN models here are no longer used. We use the
+    # re-converted pre-trained models under detectron2 model zoo instead.
+    C2_IMAGENET_MODELS = {
+        "MSRA/R-50": "ImageNetPretrained/MSRA/R-50.pkl",
+        "MSRA/R-101": "ImageNetPretrained/MSRA/R-101.pkl",
+        "FAIR/R-50-GN": "ImageNetPretrained/47261647/R-50-GN.pkl",
+        "FAIR/R-101-GN": "ImageNetPretrained/47592356/R-101-GN.pkl",
+        "FAIR/X-101-32x8d": "ImageNetPretrained/20171220/X-101-32x8d.pkl",
+        "FAIR/X-101-64x4d": "ImageNetPretrained/FBResNeXt/X-101-64x4d.pkl",
+        "FAIR/X-152-32x8d-IN5k": "ImageNetPretrained/25093814/X-152-32x8d-IN5k.pkl",
+    }
+
+    C2_DETECTRON_PATH_FORMAT = (
+        "{prefix}/{url}/output/train/{dataset}/{type}/model_final.pkl"  # noqa B950
+    )
+
+    C2_DATASET_COCO = "coco_2014_train%3Acoco_2014_valminusminival"
+    C2_DATASET_COCO_KEYPOINTS = "keypoints_coco_2014_train%3Akeypoints_coco_2014_valminusminival"
+
+    # format: {model_name} -> part of the url
+    C2_DETECTRON_MODELS = {
+        "35857197/e2e_faster_rcnn_R-50-C4_1x": "35857197/12_2017_baselines/e2e_faster_rcnn_R-50-C4_1x.yaml.01_33_49.iAX0mXvW",  # noqa B950
+        "35857345/e2e_faster_rcnn_R-50-FPN_1x": "35857345/12_2017_baselines/e2e_faster_rcnn_R-50-FPN_1x.yaml.01_36_30.cUF7QR7I",  # noqa B950
+        "35857890/e2e_faster_rcnn_R-101-FPN_1x": "35857890/12_2017_baselines/e2e_faster_rcnn_R-101-FPN_1x.yaml.01_38_50.sNxI7sX7",  # noqa B950
+        "36761737/e2e_faster_rcnn_X-101-32x8d-FPN_1x": "36761737/12_2017_baselines/e2e_faster_rcnn_X-101-32x8d-FPN_1x.yaml.06_31_39.5MIHi1fZ",  # noqa B950
+        "35858791/e2e_mask_rcnn_R-50-C4_1x": "35858791/12_2017_baselines/e2e_mask_rcnn_R-50-C4_1x.yaml.01_45_57.ZgkA7hPB",  # noqa B950
+        "35858933/e2e_mask_rcnn_R-50-FPN_1x": "35858933/12_2017_baselines/e2e_mask_rcnn_R-50-FPN_1x.yaml.01_48_14.DzEQe4wC",  # noqa B950
+        "35861795/e2e_mask_rcnn_R-101-FPN_1x": "35861795/12_2017_baselines/e2e_mask_rcnn_R-101-FPN_1x.yaml.02_31_37.KqyEK4tT",  # noqa B950
+        "36761843/e2e_mask_rcnn_X-101-32x8d-FPN_1x": "36761843/12_2017_baselines/e2e_mask_rcnn_X-101-32x8d-FPN_1x.yaml.06_35_59.RZotkLKI",  # noqa B950
+        "48616381/e2e_mask_rcnn_R-50-FPN_2x_gn": "GN/48616381/04_2018_gn_baselines/e2e_mask_rcnn_R-50-FPN_2x_gn_0416.13_23_38.bTlTI97Q",  # noqa B950
+        "37697547/e2e_keypoint_rcnn_R-50-FPN_1x": "37697547/12_2017_baselines/e2e_keypoint_rcnn_R-50-FPN_1x.yaml.08_42_54.kdzV35ao",  # noqa B950
+        "35998355/rpn_R-50-C4_1x": "35998355/12_2017_baselines/rpn_R-50-C4_1x.yaml.08_00_43.njH5oD9L",  # noqa B950
+        "35998814/rpn_R-50-FPN_1x": "35998814/12_2017_baselines/rpn_R-50-FPN_1x.yaml.08_06_03.Axg0r179",  # noqa B950
+        "36225147/fast_R-50-FPN_1x": "36225147/12_2017_baselines/fast_rcnn_R-50-FPN_1x.yaml.08_39_09.L3obSdQ2",  # noqa B950
+    }
+
+    @staticmethod
+    def get(name):
+        if name.startswith("Caffe2Detectron/COCO"):
+            return ModelCatalog._get_c2_detectron_baseline(name)
+        if name.startswith("ImageNetPretrained/"):
+            return ModelCatalog._get_c2_imagenet_pretrained(name)
+        raise RuntimeError("model not present in the catalog: {}".format(name))
+
+    @staticmethod
+    def _get_c2_imagenet_pretrained(name):
+        prefix = ModelCatalog.S3_C2_DETECTRON_PREFIX
+        name = name[len("ImageNetPretrained/") :]
+        name = ModelCatalog.C2_IMAGENET_MODELS[name]
+        url = "/".join([prefix, name])
+        return url
+
+    @staticmethod
+    def _get_c2_detectron_baseline(name):
+        name = name[len("Caffe2Detectron/COCO/") :]
+        url = ModelCatalog.C2_DETECTRON_MODELS[name]
+        if "keypoint_rcnn" in name:
+            dataset = ModelCatalog.C2_DATASET_COCO_KEYPOINTS
+        else:
+            dataset = ModelCatalog.C2_DATASET_COCO
+
+        if "35998355/rpn_R-50-C4_1x" in name:
+            # this one model is somehow different from others ..
+            type = "rpn"
+        else:
+            type = "generalized_rcnn"
+
+        # Detectron C2 models are stored in the structure defined in `C2_DETECTRON_PATH_FORMAT`.
+        url = ModelCatalog.C2_DETECTRON_PATH_FORMAT.format(
+            prefix=ModelCatalog.S3_C2_DETECTRON_PREFIX, url=url, type=type, dataset=dataset
+        )
+        return url
+
+
+class ModelCatalogHandler(PathHandler):
+    """
+    Resolve URL like catalog://.
+    """
+
+    PREFIX = "catalog://"
+
+    def _get_supported_prefixes(self):
+        return [self.PREFIX]
+
+    def _get_local_path(self, path, **kwargs):
+        logger = logging.getLogger(__name__)
+        catalog_path = ModelCatalog.get(path[len(self.PREFIX) :])
+        logger.info("Catalog entry {} points to {}".format(path, catalog_path))
+        return PathManager.get_local_path(catalog_path, **kwargs)
+
+    def _open(self, path, mode="r", **kwargs):
+        return PathManager.open(self._get_local_path(path), mode, **kwargs)
+
+
+PathManager.register_handler(ModelCatalogHandler())

detectron2/checkpoint/detection_checkpoint.py

@@ -0,0 +1,143 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import logging
+import os
+import pickle
+from urllib.parse import parse_qs, urlparse
+import torch
+from fvcore.common.checkpoint import Checkpointer
+from torch.nn.parallel import DistributedDataParallel
+
+import detectron2.utils.comm as comm
+from detectron2.utils.file_io import PathManager
+
+from .c2_model_loading import align_and_update_state_dicts
+
+
+class DetectionCheckpointer(Checkpointer):
+    """
+    Same as :class:`Checkpointer`, but is able to:
+    1. handle models in detectron & detectron2 model zoo, and apply conversions for legacy models.
+    2. correctly load checkpoints that are only available on the master worker
+    """
+
+    def __init__(self, model, save_dir="", *, save_to_disk=None, **checkpointables):
+        is_main_process = comm.is_main_process()
+        super().__init__(
+            model,
+            save_dir,
+            save_to_disk=is_main_process if save_to_disk is None else save_to_disk,
+            **checkpointables,
+        )
+        self.path_manager = PathManager
+        self._parsed_url_during_load = None
+
+    def load(self, path, *args, **kwargs):
+        assert self._parsed_url_during_load is None
+        need_sync = False
+        logger = logging.getLogger(__name__)
+        logger.info("[DetectionCheckpointer] Loading from {} ...".format(path))
+
+        if path and isinstance(self.model, DistributedDataParallel):
+            path = self.path_manager.get_local_path(path)
+            has_file = os.path.isfile(path)
+            all_has_file = comm.all_gather(has_file)
+            if not all_has_file[0]:
+                raise OSError(f"File {path} not found on main worker.")
+            if not all(all_has_file):
+                logger.warning(
+                    f"Not all workers can read checkpoint {path}. "
+                    "Training may fail to fully resume."
+                )
+                # TODO: broadcast the checkpoint file contents from main
+                # worker, and load from it instead.
+                need_sync = True
+            if not has_file:
+                path = None  # don't load if not readable
+
+        if path:
+            parsed_url = urlparse(path)
+            self._parsed_url_during_load = parsed_url
+            path = parsed_url._replace(query="").geturl()  # remove query from filename
+            path = self.path_manager.get_local_path(path)
+        ret = super().load(path, *args, **kwargs)
+
+        if need_sync:
+            logger.info("Broadcasting model states from main worker ...")
+            self.model._sync_params_and_buffers()
+        self._parsed_url_during_load = None  # reset to None
+        return ret
+
+    def _load_file(self, filename):
+        if filename.endswith(".pkl"):
+            with PathManager.open(filename, "rb") as f:
+                data = pickle.load(f, encoding="latin1")
+            if "model" in data and "__author__" in data:
+                # file is in Detectron2 model zoo format
+                self.logger.info("Reading a file from '{}'".format(data["__author__"]))
+                return data
+            else:
+                # assume file is from Caffe2 / Detectron1 model zoo
+                if "blobs" in data:
+                    # Detection models have "blobs", but ImageNet models don't
+                    data = data["blobs"]
+                data = {k: v for k, v in data.items() if not k.endswith("_momentum")}
+                return {"model": data, "__author__": "Caffe2", "matching_heuristics": True}
+        elif filename.endswith(".pyth"):
+            # assume file is from pycls; no one else seems to use the ".pyth" extension
+            with PathManager.open(filename, "rb") as f:
+                data = torch.load(f)
+            assert (
+                "model_state" in data
+            ), f"Cannot load .pyth file {filename}; pycls checkpoints must contain 'model_state'."
+            model_state = {
+                k: v
+                for k, v in data["model_state"].items()
+                if not k.endswith("num_batches_tracked")
+            }
+            return {"model": model_state, "__author__": "pycls", "matching_heuristics": True}
+
+        loaded = self._torch_load(filename)
+        if "model" not in loaded:
+            loaded = {"model": loaded}
+        assert self._parsed_url_during_load is not None, "`_load_file` must be called inside `load`"
+        parsed_url = self._parsed_url_during_load
+        queries = parse_qs(parsed_url.query)
+        if queries.pop("matching_heuristics", "False") == ["True"]:
+            loaded["matching_heuristics"] = True
+        if len(queries) > 0:
+            raise ValueError(
+                f"Unsupported query remaining: f{queries}, orginal filename: {parsed_url.geturl()}"
+            )
+        return loaded
+
+    def _torch_load(self, f):
+        return super()._load_file(f)
+
+    def _load_model(self, checkpoint):
+        if checkpoint.get("matching_heuristics", False):
+            self._convert_ndarray_to_tensor(checkpoint["model"])
+            # convert weights by name-matching heuristics
+            checkpoint["model"] = align_and_update_state_dicts(
+                self.model.state_dict(),
+                checkpoint["model"],
+                c2_conversion=checkpoint.get("__author__", None) == "Caffe2",
+            )
+        # for non-caffe2 models, use standard ways to load it
+        incompatible = super()._load_model(checkpoint)
+
+        model_buffers = dict(self.model.named_buffers(recurse=False))
+        for k in ["pixel_mean", "pixel_std"]:
+            # Ignore missing key message about pixel_mean/std.
+            # Though they may be missing in old checkpoints, they will be correctly
+            # initialized from config anyway.
+            if k in model_buffers:
+                try:
+                    incompatible.missing_keys.remove(k)
+                except ValueError:
+                    pass
+        for k in incompatible.unexpected_keys[:]:
+            # Ignore unexpected keys about cell anchors. They exist in old checkpoints
+            # but now they are non-persistent buffers and will not be in new checkpoints.
+            if "anchor_generator.cell_anchors" in k:
+                incompatible.unexpected_keys.remove(k)
+        return incompatible

detectron2/config/__init__.py

@@ -0,0 +1,24 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .compat import downgrade_config, upgrade_config
+from .config import CfgNode, get_cfg, global_cfg, set_global_cfg, configurable
+from .instantiate import instantiate
+from .lazy import LazyCall, LazyConfig
+
+__all__ = [
+    "CfgNode",
+    "get_cfg",
+    "global_cfg",
+    "set_global_cfg",
+    "downgrade_config",
+    "upgrade_config",
+    "configurable",
+    "instantiate",
+    "LazyCall",
+    "LazyConfig",
+]
+
+
+from detectron2.utils.env import fixup_module_metadata
+
+fixup_module_metadata(__name__, globals(), __all__)
+del fixup_module_metadata

detectron2/config/compat.py

@@ -0,0 +1,229 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+"""
+Backward compatibility of configs.
+
+Instructions to bump version:
++ It's not needed to bump version if new keys are added.
+  It's only needed when backward-incompatible changes happen
+  (i.e., some existing keys disappear, or the meaning of a key changes)
++ To bump version, do the following:
+    1. Increment _C.VERSION in defaults.py
+    2. Add a converter in this file.
+
+      Each ConverterVX has a function "upgrade" which in-place upgrades config from X-1 to X,
+      and a function "downgrade" which in-place downgrades config from X to X-1
+
+      In each function, VERSION is left unchanged.
+
+      Each converter assumes that its input has the relevant keys
+      (i.e., the input is not a partial config).
+    3. Run the tests (test_config.py) to make sure the upgrade & downgrade
+       functions are consistent.
+"""
+
+import logging
+from typing import List, Optional, Tuple
+
+from .config import CfgNode as CN
+from .defaults import _C
+
+__all__ = ["upgrade_config", "downgrade_config"]
+
+
+def upgrade_config(cfg: CN, to_version: Optional[int] = None) -> CN:
+    """
+    Upgrade a config from its current version to a newer version.
+
+    Args:
+        cfg (CfgNode):
+        to_version (int): defaults to the latest version.
+    """
+    cfg = cfg.clone()
+    if to_version is None:
+        to_version = _C.VERSION
+
+    assert cfg.VERSION <= to_version, "Cannot upgrade from v{} to v{}!".format(
+        cfg.VERSION, to_version
+    )
+    for k in range(cfg.VERSION, to_version):
+        converter = globals()["ConverterV" + str(k + 1)]
+        converter.upgrade(cfg)
+        cfg.VERSION = k + 1
+    return cfg
+
+
+def downgrade_config(cfg: CN, to_version: int) -> CN:
+    """
+    Downgrade a config from its current version to an older version.
+
+    Args:
+        cfg (CfgNode):
+        to_version (int):
+
+    Note:
+        A general downgrade of arbitrary configs is not always possible due to the
+        different functionalities in different versions.
+        The purpose of downgrade is only to recover the defaults in old versions,
+        allowing it to load an old partial yaml config.
+        Therefore, the implementation only needs to fill in the default values
+        in the old version when a general downgrade is not possible.
+    """
+    cfg = cfg.clone()
+    assert cfg.VERSION >= to_version, "Cannot downgrade from v{} to v{}!".format(
+        cfg.VERSION, to_version
+    )
+    for k in range(cfg.VERSION, to_version, -1):
+        converter = globals()["ConverterV" + str(k)]
+        converter.downgrade(cfg)
+        cfg.VERSION = k - 1
+    return cfg
+
+
+def guess_version(cfg: CN, filename: str) -> int:
+    """
+    Guess the version of a partial config where the VERSION field is not specified.
+    Returns the version, or the latest if cannot make a guess.
+
+    This makes it easier for users to migrate.
+    """
+    logger = logging.getLogger(__name__)
+
+    def _has(name: str) -> bool:
+        cur = cfg
+        for n in name.split("."):
+            if n not in cur:
+                return False
+            cur = cur[n]
+        return True
+
+    # Most users' partial configs have "MODEL.WEIGHT", so guess on it
+    ret = None
+    if _has("MODEL.WEIGHT") or _has("TEST.AUG_ON"):
+        ret = 1
+
+    if ret is not None:
+        logger.warning("Config '{}' has no VERSION. Assuming it to be v{}.".format(filename, ret))
+    else:
+        ret = _C.VERSION
+        logger.warning(
+            "Config '{}' has no VERSION. Assuming it to be compatible with latest v{}.".format(
+                filename, ret
+            )
+        )
+    return ret
+
+
+def _rename(cfg: CN, old: str, new: str) -> None:
+    old_keys = old.split(".")
+    new_keys = new.split(".")
+
+    def _set(key_seq: List[str], val: str) -> None:
+        cur = cfg
+        for k in key_seq[:-1]:
+            if k not in cur:
+                cur[k] = CN()
+            cur = cur[k]
+        cur[key_seq[-1]] = val
+
+    def _get(key_seq: List[str]) -> CN:
+        cur = cfg
+        for k in key_seq:
+            cur = cur[k]
+        return cur
+
+    def _del(key_seq: List[str]) -> None:
+        cur = cfg
+        for k in key_seq[:-1]:
+            cur = cur[k]
+        del cur[key_seq[-1]]
+        if len(cur) == 0 and len(key_seq) > 1:
+            _del(key_seq[:-1])
+
+    _set(new_keys, _get(old_keys))
+    _del(old_keys)
+
+
+class _RenameConverter:
+    """
+    A converter that handles simple rename.
+    """
+
+    RENAME: List[Tuple[str, str]] = []  # list of tuples of (old name, new name)
+
+    @classmethod
+    def upgrade(cls, cfg: CN) -> None:
+        for old, new in cls.RENAME:
+            _rename(cfg, old, new)
+
+    @classmethod
+    def downgrade(cls, cfg: CN) -> None:
+        for old, new in cls.RENAME[::-1]:
+            _rename(cfg, new, old)
+
+
+class ConverterV1(_RenameConverter):
+    RENAME = [("MODEL.RPN_HEAD.NAME", "MODEL.RPN.HEAD_NAME")]
+
+
+class ConverterV2(_RenameConverter):
+    """
+    A large bulk of rename, before public release.
+    """
+
+    RENAME = [
+        ("MODEL.WEIGHT", "MODEL.WEIGHTS"),
+        ("MODEL.PANOPTIC_FPN.SEMANTIC_LOSS_SCALE", "MODEL.SEM_SEG_HEAD.LOSS_WEIGHT"),
+        ("MODEL.PANOPTIC_FPN.RPN_LOSS_SCALE", "MODEL.RPN.LOSS_WEIGHT"),
+        ("MODEL.PANOPTIC_FPN.INSTANCE_LOSS_SCALE", "MODEL.PANOPTIC_FPN.INSTANCE_LOSS_WEIGHT"),
+        ("MODEL.PANOPTIC_FPN.COMBINE_ON", "MODEL.PANOPTIC_FPN.COMBINE.ENABLED"),
+        (
+            "MODEL.PANOPTIC_FPN.COMBINE_OVERLAP_THRESHOLD",
+            "MODEL.PANOPTIC_FPN.COMBINE.OVERLAP_THRESH",
+        ),
+        (
+            "MODEL.PANOPTIC_FPN.COMBINE_STUFF_AREA_LIMIT",
+            "MODEL.PANOPTIC_FPN.COMBINE.STUFF_AREA_LIMIT",
+        ),
+        (
+            "MODEL.PANOPTIC_FPN.COMBINE_INSTANCES_CONFIDENCE_THRESHOLD",
+            "MODEL.PANOPTIC_FPN.COMBINE.INSTANCES_CONFIDENCE_THRESH",
+        ),
+        ("MODEL.ROI_HEADS.SCORE_THRESH", "MODEL.ROI_HEADS.SCORE_THRESH_TEST"),
+        ("MODEL.ROI_HEADS.NMS", "MODEL.ROI_HEADS.NMS_THRESH_TEST"),
+        ("MODEL.RETINANET.INFERENCE_SCORE_THRESHOLD", "MODEL.RETINANET.SCORE_THRESH_TEST"),
+        ("MODEL.RETINANET.INFERENCE_TOPK_CANDIDATES", "MODEL.RETINANET.TOPK_CANDIDATES_TEST"),
+        ("MODEL.RETINANET.INFERENCE_NMS_THRESHOLD", "MODEL.RETINANET.NMS_THRESH_TEST"),
+        ("TEST.DETECTIONS_PER_IMG", "TEST.DETECTIONS_PER_IMAGE"),
+        ("TEST.AUG_ON", "TEST.AUG.ENABLED"),
+        ("TEST.AUG_MIN_SIZES", "TEST.AUG.MIN_SIZES"),
+        ("TEST.AUG_MAX_SIZE", "TEST.AUG.MAX_SIZE"),
+        ("TEST.AUG_FLIP", "TEST.AUG.FLIP"),
+    ]
+
+    @classmethod
+    def upgrade(cls, cfg: CN) -> None:
+        super().upgrade(cfg)
+
+        if cfg.MODEL.META_ARCHITECTURE == "RetinaNet":
+            _rename(
+                cfg, "MODEL.RETINANET.ANCHOR_ASPECT_RATIOS", "MODEL.ANCHOR_GENERATOR.ASPECT_RATIOS"
+            )
+            _rename(cfg, "MODEL.RETINANET.ANCHOR_SIZES", "MODEL.ANCHOR_GENERATOR.SIZES")
+            del cfg["MODEL"]["RPN"]["ANCHOR_SIZES"]
+            del cfg["MODEL"]["RPN"]["ANCHOR_ASPECT_RATIOS"]
+        else:
+            _rename(cfg, "MODEL.RPN.ANCHOR_ASPECT_RATIOS", "MODEL.ANCHOR_GENERATOR.ASPECT_RATIOS")
+            _rename(cfg, "MODEL.RPN.ANCHOR_SIZES", "MODEL.ANCHOR_GENERATOR.SIZES")
+            del cfg["MODEL"]["RETINANET"]["ANCHOR_SIZES"]
+            del cfg["MODEL"]["RETINANET"]["ANCHOR_ASPECT_RATIOS"]
+        del cfg["MODEL"]["RETINANET"]["ANCHOR_STRIDES"]
+
+    @classmethod
+    def downgrade(cls, cfg: CN) -> None:
+        super().downgrade(cfg)
+
+        _rename(cfg, "MODEL.ANCHOR_GENERATOR.ASPECT_RATIOS", "MODEL.RPN.ANCHOR_ASPECT_RATIOS")
+        _rename(cfg, "MODEL.ANCHOR_GENERATOR.SIZES", "MODEL.RPN.ANCHOR_SIZES")
+        cfg.MODEL.RETINANET.ANCHOR_ASPECT_RATIOS = cfg.MODEL.RPN.ANCHOR_ASPECT_RATIOS
+        cfg.MODEL.RETINANET.ANCHOR_SIZES = cfg.MODEL.RPN.ANCHOR_SIZES
+        cfg.MODEL.RETINANET.ANCHOR_STRIDES = []  # this is not used anywhere in any version

detectron2/config/config.py

@@ -0,0 +1,265 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import functools
+import inspect
+import logging
+from fvcore.common.config import CfgNode as _CfgNode
+
+from detectron2.utils.file_io import PathManager
+
+
+class CfgNode(_CfgNode):
+    """
+    The same as `fvcore.common.config.CfgNode`, but different in:
+
+    1. Use unsafe yaml loading by default.
+       Note that this may lead to arbitrary code execution: you must not
+       load a config file from untrusted sources before manually inspecting
+       the content of the file.
+    2. Support config versioning.
+       When attempting to merge an old config, it will convert the old config automatically.
+
+    .. automethod:: clone
+    .. automethod:: freeze
+    .. automethod:: defrost
+    .. automethod:: is_frozen
+    .. automethod:: load_yaml_with_base
+    .. automethod:: merge_from_list
+    .. automethod:: merge_from_other_cfg
+    """
+
+    @classmethod
+    def _open_cfg(cls, filename):
+        return PathManager.open(filename, "r")
+
+    # Note that the default value of allow_unsafe is changed to True
+    def merge_from_file(self, cfg_filename: str, allow_unsafe: bool = True) -> None:
+        """
+        Load content from the given config file and merge it into self.
+
+        Args:
+            cfg_filename: config filename
+            allow_unsafe: allow unsafe yaml syntax
+        """
+        assert PathManager.isfile(cfg_filename), f"Config file '{cfg_filename}' does not exist!"
+        loaded_cfg = self.load_yaml_with_base(cfg_filename, allow_unsafe=allow_unsafe)
+        loaded_cfg = type(self)(loaded_cfg)
+
+        # defaults.py needs to import CfgNode
+        from .defaults import _C
+
+        latest_ver = _C.VERSION
+        assert (
+            latest_ver == self.VERSION
+        ), "CfgNode.merge_from_file is only allowed on a config object of latest version!"
+
+        logger = logging.getLogger(__name__)
+
+        loaded_ver = loaded_cfg.get("VERSION", None)
+        if loaded_ver is None:
+            from .compat import guess_version
+
+            loaded_ver = guess_version(loaded_cfg, cfg_filename)
+        assert loaded_ver <= self.VERSION, "Cannot merge a v{} config into a v{} config.".format(
+            loaded_ver, self.VERSION
+        )
+
+        if loaded_ver == self.VERSION:
+            self.merge_from_other_cfg(loaded_cfg)
+        else:
+            # compat.py needs to import CfgNode
+            from .compat import upgrade_config, downgrade_config
+
+            logger.warning(
+                "Loading an old v{} config file '{}' by automatically upgrading to v{}. "
+                "See docs/CHANGELOG.md for instructions to update your files.".format(
+                    loaded_ver, cfg_filename, self.VERSION
+                )
+            )
+            # To convert, first obtain a full config at an old version
+            old_self = downgrade_config(self, to_version=loaded_ver)
+            old_self.merge_from_other_cfg(loaded_cfg)
+            new_config = upgrade_config(old_self)
+            self.clear()
+            self.update(new_config)
+
+    def dump(self, *args, **kwargs):
+        """
+        Returns:
+            str: a yaml string representation of the config
+        """
+        # to make it show up in docs
+        return super().dump(*args, **kwargs)
+
+
+global_cfg = CfgNode()
+
+
+def get_cfg() -> CfgNode:
+    """
+    Get a copy of the default config.
+
+    Returns:
+        a detectron2 CfgNode instance.
+    """
+    from .defaults import _C
+
+    return _C.clone()
+
+
+def set_global_cfg(cfg: CfgNode) -> None:
+    """
+    Let the global config point to the given cfg.
+
+    Assume that the given "cfg" has the key "KEY", after calling
+    `set_global_cfg(cfg)`, the key can be accessed by:
+    ::
+        from detectron2.config import global_cfg
+        print(global_cfg.KEY)
+
+    By using a hacky global config, you can access these configs anywhere,
+    without having to pass the config object or the values deep into the code.
+    This is a hacky feature introduced for quick prototyping / research exploration.
+    """
+    global global_cfg
+    global_cfg.clear()
+    global_cfg.update(cfg)
+
+
+def configurable(init_func=None, *, from_config=None):
+    """
+    Decorate a function or a class's __init__ method so that it can be called
+    with a :class:`CfgNode` object using a :func:`from_config` function that translates
+    :class:`CfgNode` to arguments.
+
+    Examples:
+    ::
+        # Usage 1: Decorator on __init__:
+        class A:
+            @configurable
+            def __init__(self, a, b=2, c=3):
+                pass
+
+            @classmethod
+            def from_config(cls, cfg):   # 'cfg' must be the first argument
+                # Returns kwargs to be passed to __init__
+                return {"a": cfg.A, "b": cfg.B}
+
+        a1 = A(a=1, b=2)  # regular construction
+        a2 = A(cfg)       # construct with a cfg
+        a3 = A(cfg, b=3, c=4)  # construct with extra overwrite
+
+        # Usage 2: Decorator on any function. Needs an extra from_config argument:
+        @configurable(from_config=lambda cfg: {"a: cfg.A, "b": cfg.B})
+        def a_func(a, b=2, c=3):
+            pass
+
+        a1 = a_func(a=1, b=2)  # regular call
+        a2 = a_func(cfg)       # call with a cfg
+        a3 = a_func(cfg, b=3, c=4)  # call with extra overwrite
+
+    Args:
+        init_func (callable): a class's ``__init__`` method in usage 1. The
+            class must have a ``from_config`` classmethod which takes `cfg` as
+            the first argument.
+        from_config (callable): the from_config function in usage 2. It must take `cfg`
+            as its first argument.
+    """
+
+    if init_func is not None:
+        assert (
+            inspect.isfunction(init_func)
+            and from_config is None
+            and init_func.__name__ == "__init__"
+        ), "Incorrect use of @configurable. Check API documentation for examples."
+
+        @functools.wraps(init_func)
+        def wrapped(self, *args, **kwargs):
+            try:
+                from_config_func = type(self).from_config
+            except AttributeError as e:
+                raise AttributeError(
+                    "Class with @configurable must have a 'from_config' classmethod."
+                ) from e
+            if not inspect.ismethod(from_config_func):
+                raise TypeError("Class with @configurable must have a 'from_config' classmethod.")
+
+            if _called_with_cfg(*args, **kwargs):
+                explicit_args = _get_args_from_config(from_config_func, *args, **kwargs)
+                init_func(self, **explicit_args)
+            else:
+                init_func(self, *args, **kwargs)
+
+        return wrapped
+
+    else:
+        if from_config is None:
+            return configurable  # @configurable() is made equivalent to @configurable
+        assert inspect.isfunction(
+            from_config
+        ), "from_config argument of configurable must be a function!"
+
+        def wrapper(orig_func):
+            @functools.wraps(orig_func)
+            def wrapped(*args, **kwargs):
+                if _called_with_cfg(*args, **kwargs):
+                    explicit_args = _get_args_from_config(from_config, *args, **kwargs)
+                    return orig_func(**explicit_args)
+                else:
+                    return orig_func(*args, **kwargs)
+
+            wrapped.from_config = from_config
+            return wrapped
+
+        return wrapper
+
+
+def _get_args_from_config(from_config_func, *args, **kwargs):
+    """
+    Use `from_config` to obtain explicit arguments.
+
+    Returns:
+        dict: arguments to be used for cls.__init__
+    """
+    signature = inspect.signature(from_config_func)
+    if list(signature.parameters.keys())[0] != "cfg":
+        if inspect.isfunction(from_config_func):
+            name = from_config_func.__name__
+        else:
+            name = f"{from_config_func.__self__}.from_config"
+        raise TypeError(f"{name} must take 'cfg' as the first argument!")
+    support_var_arg = any(
+        param.kind in [param.VAR_POSITIONAL, param.VAR_KEYWORD]
+        for param in signature.parameters.values()
+    )
+    if support_var_arg:  # forward all arguments to from_config, if from_config accepts them
+        ret = from_config_func(*args, **kwargs)
+    else:
+        # forward supported arguments to from_config
+        supported_arg_names = set(signature.parameters.keys())
+        extra_kwargs = {}
+        for name in list(kwargs.keys()):
+            if name not in supported_arg_names:
+                extra_kwargs[name] = kwargs.pop(name)
+        ret = from_config_func(*args, **kwargs)
+        # forward the other arguments to __init__
+        ret.update(extra_kwargs)
+    return ret
+
+
+def _called_with_cfg(*args, **kwargs):
+    """
+    Returns:
+        bool: whether the arguments contain CfgNode and should be considered
+            forwarded to from_config.
+    """
+    from omegaconf import DictConfig
+
+    if len(args) and isinstance(args[0], (_CfgNode, DictConfig)):
+        return True
+    if isinstance(kwargs.pop("cfg", None), (_CfgNode, DictConfig)):
+        return True
+    # `from_config`'s first argument is forced to be "cfg".
+    # So the above check covers all cases.
+    return False

detectron2/config/defaults.py

@@ -0,0 +1,652 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .config import CfgNode as CN
+
+# NOTE: given the new config system
+# (https://detectron2.readthedocs.io/en/latest/tutorials/lazyconfigs.html),
+# we will stop adding new functionalities to default CfgNode.
+
+# -----------------------------------------------------------------------------
+# Convention about Training / Test specific parameters
+# -----------------------------------------------------------------------------
+# Whenever an argument can be either used for training or for testing, the
+# corresponding name will be post-fixed by a _TRAIN for a training parameter,
+# or _TEST for a test-specific parameter.
+# For example, the number of images during training will be
+# IMAGES_PER_BATCH_TRAIN, while the number of images for testing will be
+# IMAGES_PER_BATCH_TEST
+
+# -----------------------------------------------------------------------------
+# Config definition
+# -----------------------------------------------------------------------------
+
+_C = CN()
+
+# The version number, to upgrade from old configs to new ones if any
+# changes happen. It's recommended to keep a VERSION in your config file.
+_C.VERSION = 2
+
+_C.MODEL = CN()
+_C.MODEL.LOAD_PROPOSALS = False
+_C.MODEL.MASK_ON = False
+_C.MODEL.KEYPOINT_ON = False
+_C.MODEL.DEVICE = "cuda"
+_C.MODEL.META_ARCHITECTURE = "GeneralizedRCNN"
+
+# Path (a file path, or URL like detectron2://.., https://..) to a checkpoint file
+# to be loaded to the model. You can find available models in the model zoo.
+_C.MODEL.WEIGHTS = ""
+
+# Values to be used for image normalization (BGR order, since INPUT.FORMAT defaults to BGR).
+# To train on images of different number of channels, just set different mean & std.
+# Default values are the mean pixel value from ImageNet: [103.53, 116.28, 123.675]
+_C.MODEL.PIXEL_MEAN = [103.530, 116.280, 123.675]
+# When using pre-trained models in Detectron1 or any MSRA models,
+# std has been absorbed into its conv1 weights, so the std needs to be set 1.
+# Otherwise, you can use [57.375, 57.120, 58.395] (ImageNet std)
+_C.MODEL.PIXEL_STD = [1.0, 1.0, 1.0]
+
+
+# -----------------------------------------------------------------------------
+# INPUT
+# -----------------------------------------------------------------------------
+_C.INPUT = CN()
+# By default, {MIN,MAX}_SIZE options are used in transforms.ResizeShortestEdge.
+# Please refer to ResizeShortestEdge for detailed definition.
+# Size of the smallest side of the image during training
+_C.INPUT.MIN_SIZE_TRAIN = (800,)
+# Sample size of smallest side by choice or random selection from range give by
+# INPUT.MIN_SIZE_TRAIN
+_C.INPUT.MIN_SIZE_TRAIN_SAMPLING = "choice"
+# Maximum size of the side of the image during training
+_C.INPUT.MAX_SIZE_TRAIN = 1333
+# Size of the smallest side of the image during testing. Set to zero to disable resize in testing.
+_C.INPUT.MIN_SIZE_TEST = 800
+# Maximum size of the side of the image during testing
+_C.INPUT.MAX_SIZE_TEST = 1333
+# Mode for flipping images used in data augmentation during training
+# choose one of ["horizontal, "vertical", "none"]
+_C.INPUT.RANDOM_FLIP = "horizontal"
+
+# `True` if cropping is used for data augmentation during training
+_C.INPUT.CROP = CN({"ENABLED": False})
+# Cropping type. See documentation of `detectron2.data.transforms.RandomCrop` for explanation.
+_C.INPUT.CROP.TYPE = "relative_range"
+# Size of crop in range (0, 1] if CROP.TYPE is "relative" or "relative_range" and in number of
+# pixels if CROP.TYPE is "absolute"
+_C.INPUT.CROP.SIZE = [0.9, 0.9]
+
+
+# Whether the model needs RGB, YUV, HSV etc.
+# Should be one of the modes defined here, as we use PIL to read the image:
+# https://pillow.readthedocs.io/en/stable/handbook/concepts.html#concept-modes
+# with BGR being the one exception. One can set image format to BGR, we will
+# internally use RGB for conversion and flip the channels over
+_C.INPUT.FORMAT = "BGR"
+# The ground truth mask format that the model will use.
+# Mask R-CNN supports either "polygon" or "bitmask" as ground truth.
+_C.INPUT.MASK_FORMAT = "polygon"  # alternative: "bitmask"
+
+
+# -----------------------------------------------------------------------------
+# Dataset
+# -----------------------------------------------------------------------------
+_C.DATASETS = CN()
+# List of the dataset names for training. Must be registered in DatasetCatalog
+# Samples from these datasets will be merged and used as one dataset.
+_C.DATASETS.TRAIN = ()
+# List of the pre-computed proposal files for training, which must be consistent
+# with datasets listed in DATASETS.TRAIN.
+_C.DATASETS.PROPOSAL_FILES_TRAIN = ()
+# Number of top scoring precomputed proposals to keep for training
+_C.DATASETS.PRECOMPUTED_PROPOSAL_TOPK_TRAIN = 2000
+# List of the dataset names for testing. Must be registered in DatasetCatalog
+_C.DATASETS.TEST = ()
+# List of the pre-computed proposal files for test, which must be consistent
+# with datasets listed in DATASETS.TEST.
+_C.DATASETS.PROPOSAL_FILES_TEST = ()
+# Number of top scoring precomputed proposals to keep for test
+_C.DATASETS.PRECOMPUTED_PROPOSAL_TOPK_TEST = 1000
+
+# -----------------------------------------------------------------------------
+# DataLoader
+# -----------------------------------------------------------------------------
+_C.DATALOADER = CN()
+# Number of data loading threads
+_C.DATALOADER.NUM_WORKERS = 4
+# If True, each batch should contain only images for which the aspect ratio
+# is compatible. This groups portrait images together, and landscape images
+# are not batched with portrait images.
+_C.DATALOADER.ASPECT_RATIO_GROUPING = True
+# Options: TrainingSampler, RepeatFactorTrainingSampler
+_C.DATALOADER.SAMPLER_TRAIN = "TrainingSampler"
+# Repeat threshold for RepeatFactorTrainingSampler
+_C.DATALOADER.REPEAT_THRESHOLD = 0.0
+# if True, take square root when computing repeating factor
+_C.DATALOADER.REPEAT_SQRT = True
+# Tf True, when working on datasets that have instance annotations, the
+# training dataloader will filter out images without associated annotations
+_C.DATALOADER.FILTER_EMPTY_ANNOTATIONS = True
+
+# ---------------------------------------------------------------------------- #
+# Backbone options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.BACKBONE = CN()
+
+_C.MODEL.BACKBONE.NAME = "build_resnet_backbone"
+# Freeze the first several stages so they are not trained.
+# There are 5 stages in ResNet. The first is a convolution, and the following
+# stages are each group of residual blocks.
+_C.MODEL.BACKBONE.FREEZE_AT = 2
+
+
+# ---------------------------------------------------------------------------- #
+# FPN options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.FPN = CN()
+# Names of the input feature maps to be used by FPN
+# They must have contiguous power of 2 strides
+# e.g., ["res2", "res3", "res4", "res5"]
+_C.MODEL.FPN.IN_FEATURES = []
+_C.MODEL.FPN.OUT_CHANNELS = 256
+
+# Options: "" (no norm), "GN"
+_C.MODEL.FPN.NORM = ""
+
+# Types for fusing the FPN top-down and lateral features. Can be either "sum" or "avg"
+_C.MODEL.FPN.FUSE_TYPE = "sum"
+
+
+# ---------------------------------------------------------------------------- #
+# Proposal generator options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.PROPOSAL_GENERATOR = CN()
+# Current proposal generators include "RPN", "RRPN" and "PrecomputedProposals"
+_C.MODEL.PROPOSAL_GENERATOR.NAME = "RPN"
+# Proposal height and width both need to be greater than MIN_SIZE
+# (a the scale used during training or inference)
+_C.MODEL.PROPOSAL_GENERATOR.MIN_SIZE = 0
+
+
+# ---------------------------------------------------------------------------- #
+# Anchor generator options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ANCHOR_GENERATOR = CN()
+# The generator can be any name in the ANCHOR_GENERATOR registry
+_C.MODEL.ANCHOR_GENERATOR.NAME = "DefaultAnchorGenerator"
+# Anchor sizes (i.e. sqrt of area) in absolute pixels w.r.t. the network input.
+# Format: list[list[float]]. SIZES[i] specifies the list of sizes to use for
+# IN_FEATURES[i]; len(SIZES) must be equal to len(IN_FEATURES) or 1.
+# When len(SIZES) == 1, SIZES[0] is used for all IN_FEATURES.
+_C.MODEL.ANCHOR_GENERATOR.SIZES = [[32, 64, 128, 256, 512]]
+# Anchor aspect ratios. For each area given in `SIZES`, anchors with different aspect
+# ratios are generated by an anchor generator.
+# Format: list[list[float]]. ASPECT_RATIOS[i] specifies the list of aspect ratios (H/W)
+# to use for IN_FEATURES[i]; len(ASPECT_RATIOS) == len(IN_FEATURES) must be true,
+# or len(ASPECT_RATIOS) == 1 is true and aspect ratio list ASPECT_RATIOS[0] is used
+# for all IN_FEATURES.
+_C.MODEL.ANCHOR_GENERATOR.ASPECT_RATIOS = [[0.5, 1.0, 2.0]]
+# Anchor angles.
+# list[list[float]], the angle in degrees, for each input feature map.
+# ANGLES[i] specifies the list of angles for IN_FEATURES[i].
+_C.MODEL.ANCHOR_GENERATOR.ANGLES = [[-90, 0, 90]]
+# Relative offset between the center of the first anchor and the top-left corner of the image
+# Value has to be in [0, 1). Recommend to use 0.5, which means half stride.
+# The value is not expected to affect model accuracy.
+_C.MODEL.ANCHOR_GENERATOR.OFFSET = 0.0
+
+# ---------------------------------------------------------------------------- #
+# RPN options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.RPN = CN()
+_C.MODEL.RPN.HEAD_NAME = "StandardRPNHead"  # used by RPN_HEAD_REGISTRY
+
+# Names of the input feature maps to be used by RPN
+# e.g., ["p2", "p3", "p4", "p5", "p6"] for FPN
+_C.MODEL.RPN.IN_FEATURES = ["res4"]
+# Remove RPN anchors that go outside the image by BOUNDARY_THRESH pixels
+# Set to -1 or a large value, e.g. 100000, to disable pruning anchors
+_C.MODEL.RPN.BOUNDARY_THRESH = -1
+# IOU overlap ratios [BG_IOU_THRESHOLD, FG_IOU_THRESHOLD]
+# Minimum overlap required between an anchor and ground-truth box for the
+# (anchor, gt box) pair to be a positive example (IoU >= FG_IOU_THRESHOLD
+# ==> positive RPN example: 1)
+# Maximum overlap allowed between an anchor and ground-truth box for the
+# (anchor, gt box) pair to be a negative examples (IoU < BG_IOU_THRESHOLD
+# ==> negative RPN example: 0)
+# Anchors with overlap in between (BG_IOU_THRESHOLD <= IoU < FG_IOU_THRESHOLD)
+# are ignored (-1)
+_C.MODEL.RPN.IOU_THRESHOLDS = [0.3, 0.7]
+_C.MODEL.RPN.IOU_LABELS = [0, -1, 1]
+# Number of regions per image used to train RPN
+_C.MODEL.RPN.BATCH_SIZE_PER_IMAGE = 256
+# Target fraction of foreground (positive) examples per RPN minibatch
+_C.MODEL.RPN.POSITIVE_FRACTION = 0.5
+# Options are: "smooth_l1", "giou", "diou", "ciou"
+_C.MODEL.RPN.BBOX_REG_LOSS_TYPE = "smooth_l1"
+_C.MODEL.RPN.BBOX_REG_LOSS_WEIGHT = 1.0
+# Weights on (dx, dy, dw, dh) for normalizing RPN anchor regression targets
+_C.MODEL.RPN.BBOX_REG_WEIGHTS = (1.0, 1.0, 1.0, 1.0)
+# The transition point from L1 to L2 loss. Set to 0.0 to make the loss simply L1.
+_C.MODEL.RPN.SMOOTH_L1_BETA = 0.0
+_C.MODEL.RPN.LOSS_WEIGHT = 1.0
+# Number of top scoring RPN proposals to keep before applying NMS
+# When FPN is used, this is *per FPN level* (not total)
+_C.MODEL.RPN.PRE_NMS_TOPK_TRAIN = 12000
+_C.MODEL.RPN.PRE_NMS_TOPK_TEST = 6000
+# Number of top scoring RPN proposals to keep after applying NMS
+# When FPN is used, this limit is applied per level and then again to the union
+# of proposals from all levels
+# NOTE: When FPN is used, the meaning of this config is different from Detectron1.
+# It means per-batch topk in Detectron1, but per-image topk here.
+# See the "find_top_rpn_proposals" function for details.
+_C.MODEL.RPN.POST_NMS_TOPK_TRAIN = 2000
+_C.MODEL.RPN.POST_NMS_TOPK_TEST = 1000
+# NMS threshold used on RPN proposals
+_C.MODEL.RPN.NMS_THRESH = 0.7
+# Set this to -1 to use the same number of output channels as input channels.
+_C.MODEL.RPN.CONV_DIMS = [-1]
+
+# ---------------------------------------------------------------------------- #
+# ROI HEADS options
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ROI_HEADS = CN()
+_C.MODEL.ROI_HEADS.NAME = "Res5ROIHeads"
+# Number of foreground classes
+_C.MODEL.ROI_HEADS.NUM_CLASSES = 80
+# Names of the input feature maps to be used by ROI heads
+# Currently all heads (box, mask, ...) use the same input feature map list
+# e.g., ["p2", "p3", "p4", "p5"] is commonly used for FPN
+_C.MODEL.ROI_HEADS.IN_FEATURES = ["res4"]
+# IOU overlap ratios [IOU_THRESHOLD]
+# Overlap threshold for an RoI to be considered background (if < IOU_THRESHOLD)
+# Overlap threshold for an RoI to be considered foreground (if >= IOU_THRESHOLD)
+_C.MODEL.ROI_HEADS.IOU_THRESHOLDS = [0.5]
+_C.MODEL.ROI_HEADS.IOU_LABELS = [0, 1]
+# RoI minibatch size *per image* (number of regions of interest [ROIs]) during training
+# Total number of RoIs per training minibatch =
+#   ROI_HEADS.BATCH_SIZE_PER_IMAGE * SOLVER.IMS_PER_BATCH
+# E.g., a common configuration is: 512 * 16 = 8192
+_C.MODEL.ROI_HEADS.BATCH_SIZE_PER_IMAGE = 512
+# Target fraction of RoI minibatch that is labeled foreground (i.e. class > 0)
+_C.MODEL.ROI_HEADS.POSITIVE_FRACTION = 0.25
+
+# Only used on test mode
+
+# Minimum score threshold (assuming scores in a [0, 1] range); a value chosen to
+# balance obtaining high recall with not having too many low precision
+# detections that will slow down inference post processing steps (like NMS)
+# A default threshold of 0.0 increases AP by ~0.2-0.3 but significantly slows down
+# inference.
+_C.MODEL.ROI_HEADS.SCORE_THRESH_TEST = 0.05
+# Overlap threshold used for non-maximum suppression (suppress boxes with
+# IoU >= this threshold)
+_C.MODEL.ROI_HEADS.NMS_THRESH_TEST = 0.5
+# If True, augment proposals with ground-truth boxes before sampling proposals to
+# train ROI heads.
+_C.MODEL.ROI_HEADS.PROPOSAL_APPEND_GT = True
+
+# ---------------------------------------------------------------------------- #
+# Box Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ROI_BOX_HEAD = CN()
+# C4 don't use head name option
+# Options for non-C4 models: FastRCNNConvFCHead,
+_C.MODEL.ROI_BOX_HEAD.NAME = ""
+# Options are: "smooth_l1", "giou", "diou", "ciou"
+_C.MODEL.ROI_BOX_HEAD.BBOX_REG_LOSS_TYPE = "smooth_l1"
+# The final scaling coefficient on the box regression loss, used to balance the magnitude of its
+# gradients with other losses in the model. See also `MODEL.ROI_KEYPOINT_HEAD.LOSS_WEIGHT`.
+_C.MODEL.ROI_BOX_HEAD.BBOX_REG_LOSS_WEIGHT = 1.0
+# Default weights on (dx, dy, dw, dh) for normalizing bbox regression targets
+# These are empirically chosen to approximately lead to unit variance targets
+_C.MODEL.ROI_BOX_HEAD.BBOX_REG_WEIGHTS = (10.0, 10.0, 5.0, 5.0)
+# The transition point from L1 to L2 loss. Set to 0.0 to make the loss simply L1.
+_C.MODEL.ROI_BOX_HEAD.SMOOTH_L1_BETA = 0.0
+_C.MODEL.ROI_BOX_HEAD.POOLER_RESOLUTION = 14
+_C.MODEL.ROI_BOX_HEAD.POOLER_SAMPLING_RATIO = 0
+# Type of pooling operation applied to the incoming feature map for each RoI
+_C.MODEL.ROI_BOX_HEAD.POOLER_TYPE = "ROIAlignV2"
+
+_C.MODEL.ROI_BOX_HEAD.NUM_FC = 0
+# Hidden layer dimension for FC layers in the RoI box head
+_C.MODEL.ROI_BOX_HEAD.FC_DIM = 1024
+_C.MODEL.ROI_BOX_HEAD.NUM_CONV = 0
+# Channel dimension for Conv layers in the RoI box head
+_C.MODEL.ROI_BOX_HEAD.CONV_DIM = 256
+# Normalization method for the convolution layers.
+# Options: "" (no norm), "GN", "SyncBN".
+_C.MODEL.ROI_BOX_HEAD.NORM = ""
+# Whether to use class agnostic for bbox regression
+_C.MODEL.ROI_BOX_HEAD.CLS_AGNOSTIC_BBOX_REG = False
+# If true, RoI heads use bounding boxes predicted by the box head rather than proposal boxes.
+_C.MODEL.ROI_BOX_HEAD.TRAIN_ON_PRED_BOXES = False
+
+# Federated loss can be used to improve the training of LVIS
+_C.MODEL.ROI_BOX_HEAD.USE_FED_LOSS = False
+# Sigmoid cross entrophy is used with federated loss
+_C.MODEL.ROI_BOX_HEAD.USE_SIGMOID_CE = False
+# The power value applied to image_count when calcualting frequency weight
+_C.MODEL.ROI_BOX_HEAD.FED_LOSS_FREQ_WEIGHT_POWER = 0.5
+# Number of classes to keep in total
+_C.MODEL.ROI_BOX_HEAD.FED_LOSS_NUM_CLASSES = 50
+
+# ---------------------------------------------------------------------------- #
+# Cascaded Box Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ROI_BOX_CASCADE_HEAD = CN()
+# The number of cascade stages is implicitly defined by the length of the following two configs.
+_C.MODEL.ROI_BOX_CASCADE_HEAD.BBOX_REG_WEIGHTS = (
+    (10.0, 10.0, 5.0, 5.0),
+    (20.0, 20.0, 10.0, 10.0),
+    (30.0, 30.0, 15.0, 15.0),
+)
+_C.MODEL.ROI_BOX_CASCADE_HEAD.IOUS = (0.5, 0.6, 0.7)
+
+
+# ---------------------------------------------------------------------------- #
+# Mask Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ROI_MASK_HEAD = CN()
+_C.MODEL.ROI_MASK_HEAD.NAME = "MaskRCNNConvUpsampleHead"
+_C.MODEL.ROI_MASK_HEAD.POOLER_RESOLUTION = 14
+_C.MODEL.ROI_MASK_HEAD.POOLER_SAMPLING_RATIO = 0
+_C.MODEL.ROI_MASK_HEAD.NUM_CONV = 0  # The number of convs in the mask head
+_C.MODEL.ROI_MASK_HEAD.CONV_DIM = 256
+# Normalization method for the convolution layers.
+# Options: "" (no norm), "GN", "SyncBN".
+_C.MODEL.ROI_MASK_HEAD.NORM = ""
+# Whether to use class agnostic for mask prediction
+_C.MODEL.ROI_MASK_HEAD.CLS_AGNOSTIC_MASK = False
+# Type of pooling operation applied to the incoming feature map for each RoI
+_C.MODEL.ROI_MASK_HEAD.POOLER_TYPE = "ROIAlignV2"
+
+
+# ---------------------------------------------------------------------------- #
+# Keypoint Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.ROI_KEYPOINT_HEAD = CN()
+_C.MODEL.ROI_KEYPOINT_HEAD.NAME = "KRCNNConvDeconvUpsampleHead"
+_C.MODEL.ROI_KEYPOINT_HEAD.POOLER_RESOLUTION = 14
+_C.MODEL.ROI_KEYPOINT_HEAD.POOLER_SAMPLING_RATIO = 0
+_C.MODEL.ROI_KEYPOINT_HEAD.CONV_DIMS = tuple(512 for _ in range(8))
+_C.MODEL.ROI_KEYPOINT_HEAD.NUM_KEYPOINTS = 17  # 17 is the number of keypoints in COCO.
+
+# Images with too few (or no) keypoints are excluded from training.
+_C.MODEL.ROI_KEYPOINT_HEAD.MIN_KEYPOINTS_PER_IMAGE = 1
+# Normalize by the total number of visible keypoints in the minibatch if True.
+# Otherwise, normalize by the total number of keypoints that could ever exist
+# in the minibatch.
+# The keypoint softmax loss is only calculated on visible keypoints.
+# Since the number of visible keypoints can vary significantly between
+# minibatches, this has the effect of up-weighting the importance of
+# minibatches with few visible keypoints. (Imagine the extreme case of
+# only one visible keypoint versus N: in the case of N, each one
+# contributes 1/N to the gradient compared to the single keypoint
+# determining the gradient direction). Instead, we can normalize the
+# loss by the total number of keypoints, if it were the case that all
+# keypoints were visible in a full minibatch. (Returning to the example,
+# this means that the one visible keypoint contributes as much as each
+# of the N keypoints.)
+_C.MODEL.ROI_KEYPOINT_HEAD.NORMALIZE_LOSS_BY_VISIBLE_KEYPOINTS = True
+# Multi-task loss weight to use for keypoints
+# Recommended values:
+#   - use 1.0 if NORMALIZE_LOSS_BY_VISIBLE_KEYPOINTS is True
+#   - use 4.0 if NORMALIZE_LOSS_BY_VISIBLE_KEYPOINTS is False
+_C.MODEL.ROI_KEYPOINT_HEAD.LOSS_WEIGHT = 1.0
+# Type of pooling operation applied to the incoming feature map for each RoI
+_C.MODEL.ROI_KEYPOINT_HEAD.POOLER_TYPE = "ROIAlignV2"
+
+# ---------------------------------------------------------------------------- #
+# Semantic Segmentation Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.SEM_SEG_HEAD = CN()
+_C.MODEL.SEM_SEG_HEAD.NAME = "SemSegFPNHead"
+_C.MODEL.SEM_SEG_HEAD.IN_FEATURES = ["p2", "p3", "p4", "p5"]
+# Label in the semantic segmentation ground truth that is ignored, i.e., no loss is calculated for
+# the correposnding pixel.
+_C.MODEL.SEM_SEG_HEAD.IGNORE_VALUE = 255
+# Number of classes in the semantic segmentation head
+_C.MODEL.SEM_SEG_HEAD.NUM_CLASSES = 54
+# Number of channels in the 3x3 convs inside semantic-FPN heads.
+_C.MODEL.SEM_SEG_HEAD.CONVS_DIM = 128
+# Outputs from semantic-FPN heads are up-scaled to the COMMON_STRIDE stride.
+_C.MODEL.SEM_SEG_HEAD.COMMON_STRIDE = 4
+# Normalization method for the convolution layers. Options: "" (no norm), "GN".
+_C.MODEL.SEM_SEG_HEAD.NORM = "GN"
+_C.MODEL.SEM_SEG_HEAD.LOSS_WEIGHT = 1.0
+
+_C.MODEL.PANOPTIC_FPN = CN()
+# Scaling of all losses from instance detection / segmentation head.
+_C.MODEL.PANOPTIC_FPN.INSTANCE_LOSS_WEIGHT = 1.0
+
+# options when combining instance & semantic segmentation outputs
+_C.MODEL.PANOPTIC_FPN.COMBINE = CN({"ENABLED": True})  # "COMBINE.ENABLED" is deprecated & not used
+_C.MODEL.PANOPTIC_FPN.COMBINE.OVERLAP_THRESH = 0.5
+_C.MODEL.PANOPTIC_FPN.COMBINE.STUFF_AREA_LIMIT = 4096
+_C.MODEL.PANOPTIC_FPN.COMBINE.INSTANCES_CONFIDENCE_THRESH = 0.5
+
+
+# ---------------------------------------------------------------------------- #
+# RetinaNet Head
+# ---------------------------------------------------------------------------- #
+_C.MODEL.RETINANET = CN()
+
+# This is the number of foreground classes.
+_C.MODEL.RETINANET.NUM_CLASSES = 80
+
+_C.MODEL.RETINANET.IN_FEATURES = ["p3", "p4", "p5", "p6", "p7"]
+
+# Convolutions to use in the cls and bbox tower
+# NOTE: this doesn't include the last conv for logits
+_C.MODEL.RETINANET.NUM_CONVS = 4
+
+# IoU overlap ratio [bg, fg] for labeling anchors.
+# Anchors with < bg are labeled negative (0)
+# Anchors  with >= bg and < fg are ignored (-1)
+# Anchors with >= fg are labeled positive (1)
+_C.MODEL.RETINANET.IOU_THRESHOLDS = [0.4, 0.5]
+_C.MODEL.RETINANET.IOU_LABELS = [0, -1, 1]
+
+# Prior prob for rare case (i.e. foreground) at the beginning of training.
+# This is used to set the bias for the logits layer of the classifier subnet.
+# This improves training stability in the case of heavy class imbalance.
+_C.MODEL.RETINANET.PRIOR_PROB = 0.01
+
+# Inference cls score threshold, only anchors with score > INFERENCE_TH are
+# considered for inference (to improve speed)
+_C.MODEL.RETINANET.SCORE_THRESH_TEST = 0.05
+# Select topk candidates before NMS
+_C.MODEL.RETINANET.TOPK_CANDIDATES_TEST = 1000
+_C.MODEL.RETINANET.NMS_THRESH_TEST = 0.5
+
+# Weights on (dx, dy, dw, dh) for normalizing Retinanet anchor regression targets
+_C.MODEL.RETINANET.BBOX_REG_WEIGHTS = (1.0, 1.0, 1.0, 1.0)
+
+# Loss parameters
+_C.MODEL.RETINANET.FOCAL_LOSS_GAMMA = 2.0
+_C.MODEL.RETINANET.FOCAL_LOSS_ALPHA = 0.25
+_C.MODEL.RETINANET.SMOOTH_L1_LOSS_BETA = 0.1
+# Options are: "smooth_l1", "giou", "diou", "ciou"
+_C.MODEL.RETINANET.BBOX_REG_LOSS_TYPE = "smooth_l1"
+
+# One of BN, SyncBN, FrozenBN, GN
+# Only supports GN until unshared norm is implemented
+_C.MODEL.RETINANET.NORM = ""
+
+
+# ---------------------------------------------------------------------------- #
+# ResNe[X]t options (ResNets = {ResNet, ResNeXt}
+# Note that parts of a resnet may be used for both the backbone and the head
+# These options apply to both
+# ---------------------------------------------------------------------------- #
+_C.MODEL.RESNETS = CN()
+
+_C.MODEL.RESNETS.DEPTH = 50
+_C.MODEL.RESNETS.OUT_FEATURES = ["res4"]  # res4 for C4 backbone, res2..5 for FPN backbone
+
+# Number of groups to use; 1 ==> ResNet; > 1 ==> ResNeXt
+_C.MODEL.RESNETS.NUM_GROUPS = 1
+
+# Options: FrozenBN, GN, "SyncBN", "BN"
+_C.MODEL.RESNETS.NORM = "FrozenBN"
+
+# Baseline width of each group.
+# Scaling this parameters will scale the width of all bottleneck layers.
+_C.MODEL.RESNETS.WIDTH_PER_GROUP = 64
+
+# Place the stride 2 conv on the 1x1 filter
+# Use True only for the original MSRA ResNet; use False for C2 and Torch models
+_C.MODEL.RESNETS.STRIDE_IN_1X1 = True
+
+# Apply dilation in stage "res5"
+_C.MODEL.RESNETS.RES5_DILATION = 1
+
+# Output width of res2. Scaling this parameters will scale the width of all 1x1 convs in ResNet
+# For R18 and R34, this needs to be set to 64
+_C.MODEL.RESNETS.RES2_OUT_CHANNELS = 256
+_C.MODEL.RESNETS.STEM_OUT_CHANNELS = 64
+
+# Apply Deformable Convolution in stages
+# Specify if apply deform_conv on Res2, Res3, Res4, Res5
+_C.MODEL.RESNETS.DEFORM_ON_PER_STAGE = [False, False, False, False]
+# Use True to use modulated deform_conv (DeformableV2, https://arxiv.org/abs/1811.11168);
+# Use False for DeformableV1.
+_C.MODEL.RESNETS.DEFORM_MODULATED = False
+# Number of groups in deformable conv.
+_C.MODEL.RESNETS.DEFORM_NUM_GROUPS = 1
+
+
+# ---------------------------------------------------------------------------- #
+# Solver
+# ---------------------------------------------------------------------------- #
+_C.SOLVER = CN()
+
+# Options: WarmupMultiStepLR, WarmupCosineLR.
+# See detectron2/solver/build.py for definition.
+_C.SOLVER.LR_SCHEDULER_NAME = "WarmupMultiStepLR"
+
+_C.SOLVER.MAX_ITER = 40000
+
+_C.SOLVER.BASE_LR = 0.001
+# The end lr, only used by WarmupCosineLR
+_C.SOLVER.BASE_LR_END = 0.0
+
+_C.SOLVER.MOMENTUM = 0.9
+
+_C.SOLVER.NESTEROV = False
+
+_C.SOLVER.WEIGHT_DECAY = 0.0001
+# The weight decay that's applied to parameters of normalization layers
+# (typically the affine transformation)
+_C.SOLVER.WEIGHT_DECAY_NORM = 0.0
+
+_C.SOLVER.GAMMA = 0.1
+# The iteration number to decrease learning rate by GAMMA.
+_C.SOLVER.STEPS = (30000,)
+# Number of decays in WarmupStepWithFixedGammaLR schedule
+_C.SOLVER.NUM_DECAYS = 3
+
+_C.SOLVER.WARMUP_FACTOR = 1.0 / 1000
+_C.SOLVER.WARMUP_ITERS = 1000
+_C.SOLVER.WARMUP_METHOD = "linear"
+# Whether to rescale the interval for the learning schedule after warmup
+_C.SOLVER.RESCALE_INTERVAL = False
+
+# Save a checkpoint after every this number of iterations
+_C.SOLVER.CHECKPOINT_PERIOD = 5000
+
+# Number of images per batch across all machines. This is also the number
+# of training images per step (i.e. per iteration). If we use 16 GPUs
+# and IMS_PER_BATCH = 32, each GPU will see 2 images per batch.
+# May be adjusted automatically if REFERENCE_WORLD_SIZE is set.
+_C.SOLVER.IMS_PER_BATCH = 16
+
+# The reference number of workers (GPUs) this config is meant to train with.
+# It takes no effect when set to 0.
+# With a non-zero value, it will be used by DefaultTrainer to compute a desired
+# per-worker batch size, and then scale the other related configs (total batch size,
+# learning rate, etc) to match the per-worker batch size.
+# See documentation of `DefaultTrainer.auto_scale_workers` for details:
+_C.SOLVER.REFERENCE_WORLD_SIZE = 0
+
+# Detectron v1 (and previous detection code) used a 2x higher LR and 0 WD for
+# biases. This is not useful (at least for recent models). You should avoid
+# changing these and they exist only to reproduce Detectron v1 training if
+# desired.
+_C.SOLVER.BIAS_LR_FACTOR = 1.0
+_C.SOLVER.WEIGHT_DECAY_BIAS = None  # None means following WEIGHT_DECAY
+
+# Gradient clipping
+_C.SOLVER.CLIP_GRADIENTS = CN({"ENABLED": False})
+# Type of gradient clipping, currently 2 values are supported:
+# - "value": the absolute values of elements of each gradients are clipped
+# - "norm": the norm of the gradient for each parameter is clipped thus
+#   affecting all elements in the parameter
+_C.SOLVER.CLIP_GRADIENTS.CLIP_TYPE = "value"
+# Maximum absolute value used for clipping gradients
+_C.SOLVER.CLIP_GRADIENTS.CLIP_VALUE = 1.0
+# Floating point number p for L-p norm to be used with the "norm"
+# gradient clipping type; for L-inf, please specify .inf
+_C.SOLVER.CLIP_GRADIENTS.NORM_TYPE = 2.0
+
+# Enable automatic mixed precision for training
+# Note that this does not change model's inference behavior.
+# To use AMP in inference, run inference under autocast()
+_C.SOLVER.AMP = CN({"ENABLED": False})
+
+# ---------------------------------------------------------------------------- #
+# Specific test options
+# ---------------------------------------------------------------------------- #
+_C.TEST = CN()
+# For end-to-end tests to verify the expected accuracy.
+# Each item is [task, metric, value, tolerance]
+# e.g.: [['bbox', 'AP', 38.5, 0.2]]
+_C.TEST.EXPECTED_RESULTS = []
+# The period (in terms of steps) to evaluate the model during training.
+# Set to 0 to disable.
+_C.TEST.EVAL_PERIOD = 0
+# The sigmas used to calculate keypoint OKS. See http://cocodataset.org/#keypoints-eval
+# When empty, it will use the defaults in COCO.
+# Otherwise it should be a list[float] with the same length as ROI_KEYPOINT_HEAD.NUM_KEYPOINTS.
+_C.TEST.KEYPOINT_OKS_SIGMAS = []
+# Maximum number of detections to return per image during inference (100 is
+# based on the limit established for the COCO dataset).
+_C.TEST.DETECTIONS_PER_IMAGE = 100
+
+_C.TEST.AUG = CN({"ENABLED": False})
+_C.TEST.AUG.MIN_SIZES = (400, 500, 600, 700, 800, 900, 1000, 1100, 1200)
+_C.TEST.AUG.MAX_SIZE = 4000
+_C.TEST.AUG.FLIP = True
+
+_C.TEST.PRECISE_BN = CN({"ENABLED": False})
+_C.TEST.PRECISE_BN.NUM_ITER = 200
+
+# ---------------------------------------------------------------------------- #
+# Misc options
+# ---------------------------------------------------------------------------- #
+# Directory where output files are written
+_C.OUTPUT_DIR = "./output"
+# Set seed to negative to fully randomize everything.
+# Set seed to positive to use a fixed seed. Note that a fixed seed increases
+# reproducibility but does not guarantee fully deterministic behavior.
+# Disabling all parallelism further increases reproducibility.
+_C.SEED = -1
+# Benchmark different cudnn algorithms.
+# If input images have very different sizes, this option will have large overhead
+# for about 10k iterations. It usually hurts total time, but can benefit for certain models.
+# If input images have the same or similar sizes, benchmark is often helpful.
+_C.CUDNN_BENCHMARK = False
+# The period (in terms of steps) for minibatch visualization at train time.
+# Set to 0 to disable.
+_C.VIS_PERIOD = 0
+
+# global config is for quick hack purposes.
+# You can set them in command line or config files,
+# and access it with:
+#
+# from detectron2.config import global_cfg
+# print(global_cfg.HACK)
+#
+# Do not commit any configs into it.
+_C.GLOBAL = CN()
+_C.GLOBAL.HACK = 1.0

detectron2/config/instantiate.py

@@ -0,0 +1,88 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import collections.abc as abc
+import dataclasses
+import logging
+from typing import Any
+
+from detectron2.utils.registry import _convert_target_to_string, locate
+
+__all__ = ["dump_dataclass", "instantiate"]
+
+
+def dump_dataclass(obj: Any):
+    """
+    Dump a dataclass recursively into a dict that can be later instantiated.
+
+    Args:
+        obj: a dataclass object
+
+    Returns:
+        dict
+    """
+    assert dataclasses.is_dataclass(obj) and not isinstance(
+        obj, type
+    ), "dump_dataclass() requires an instance of a dataclass."
+    ret = {"_target_": _convert_target_to_string(type(obj))}
+    for f in dataclasses.fields(obj):
+        v = getattr(obj, f.name)
+        if dataclasses.is_dataclass(v):
+            v = dump_dataclass(v)
+        if isinstance(v, (list, tuple)):
+            v = [dump_dataclass(x) if dataclasses.is_dataclass(x) else x for x in v]
+        ret[f.name] = v
+    return ret
+
+
+def instantiate(cfg):
+    """
+    Recursively instantiate objects defined in dictionaries by
+    "_target_" and arguments.
+
+    Args:
+        cfg: a dict-like object with "_target_" that defines the caller, and
+            other keys that define the arguments
+
+    Returns:
+        object instantiated by cfg
+    """
+    from omegaconf import ListConfig, DictConfig, OmegaConf
+
+    if isinstance(cfg, ListConfig):
+        lst = [instantiate(x) for x in cfg]
+        return ListConfig(lst, flags={"allow_objects": True})
+    if isinstance(cfg, list):
+        # Specialize for list, because many classes take
+        # list[objects] as arguments, such as ResNet, DatasetMapper
+        return [instantiate(x) for x in cfg]
+
+    # If input is a DictConfig backed by dataclasses (i.e. omegaconf's structured config),
+    # instantiate it to the actual dataclass.
+    if isinstance(cfg, DictConfig) and dataclasses.is_dataclass(cfg._metadata.object_type):
+        return OmegaConf.to_object(cfg)
+
+    if isinstance(cfg, abc.Mapping) and "_target_" in cfg:
+        # conceptually equivalent to hydra.utils.instantiate(cfg) with _convert_=all,
+        # but faster: https://github.com/facebookresearch/hydra/issues/1200
+        cfg = {k: instantiate(v) for k, v in cfg.items()}
+        cls = cfg.pop("_target_")
+        cls = instantiate(cls)
+
+        if isinstance(cls, str):
+            cls_name = cls
+            cls = locate(cls_name)
+            assert cls is not None, cls_name
+        else:
+            try:
+                cls_name = cls.__module__ + "." + cls.__qualname__
+            except Exception:
+                # target could be anything, so the above could fail
+                cls_name = str(cls)
+        assert callable(cls), f"_target_ {cls} does not define a callable object"
+        try:
+            return cls(**cfg)
+        except TypeError:
+            logger = logging.getLogger(__name__)
+            logger.error(f"Error when instantiating {cls_name}!")
+            raise
+    return cfg  # return as-is if don't know what to do

detectron2/config/lazy.py

@@ -0,0 +1,436 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import ast
+import builtins
+import collections.abc as abc
+import importlib
+import inspect
+import logging
+import os
+import uuid
+from contextlib import contextmanager
+from copy import deepcopy
+from dataclasses import is_dataclass
+from typing import List, Tuple, Union
+import cloudpickle
+import yaml
+from omegaconf import DictConfig, ListConfig, OmegaConf, SCMode
+
+from detectron2.utils.file_io import PathManager
+from detectron2.utils.registry import _convert_target_to_string
+
+__all__ = ["LazyCall", "LazyConfig"]
+
+
+class LazyCall:
+    """
+    Wrap a callable so that when it's called, the call will not be executed,
+    but returns a dict that describes the call.
+
+    LazyCall object has to be called with only keyword arguments. Positional
+    arguments are not yet supported.
+
+    Examples:
+    ::
+        from detectron2.config import instantiate, LazyCall
+
+        layer_cfg = LazyCall(nn.Conv2d)(in_channels=32, out_channels=32)
+        layer_cfg.out_channels = 64   # can edit it afterwards
+        layer = instantiate(layer_cfg)
+    """
+
+    def __init__(self, target):
+        if not (callable(target) or isinstance(target, (str, abc.Mapping))):
+            raise TypeError(
+                f"target of LazyCall must be a callable or defines a callable! Got {target}"
+            )
+        self._target = target
+
+    def __call__(self, **kwargs):
+        if is_dataclass(self._target):
+            # omegaconf object cannot hold dataclass type
+            # https://github.com/omry/omegaconf/issues/784
+            target = _convert_target_to_string(self._target)
+        else:
+            target = self._target
+        kwargs["_target_"] = target
+
+        return DictConfig(content=kwargs, flags={"allow_objects": True})
+
+
+def _visit_dict_config(cfg, func):
+    """
+    Apply func recursively to all DictConfig in cfg.
+    """
+    if isinstance(cfg, DictConfig):
+        func(cfg)
+        for v in cfg.values():
+            _visit_dict_config(v, func)
+    elif isinstance(cfg, ListConfig):
+        for v in cfg:
+            _visit_dict_config(v, func)
+
+
+def _validate_py_syntax(filename):
+    # see also https://github.com/open-mmlab/mmcv/blob/master/mmcv/utils/config.py
+    with PathManager.open(filename, "r") as f:
+        content = f.read()
+    try:
+        ast.parse(content)
+    except SyntaxError as e:
+        raise SyntaxError(f"Config file {filename} has syntax error!") from e
+
+
+def _cast_to_config(obj):
+    # if given a dict, return DictConfig instead
+    if isinstance(obj, dict):
+        return DictConfig(obj, flags={"allow_objects": True})
+    return obj
+
+
+_CFG_PACKAGE_NAME = "detectron2._cfg_loader"
+"""
+A namespace to put all imported config into.
+"""
+
+
+def _random_package_name(filename):
+    # generate a random package name when loading config files
+    return _CFG_PACKAGE_NAME + str(uuid.uuid4())[:4] + "." + os.path.basename(filename)
+
+
+@contextmanager
+def _patch_import():
+    """
+    Enhance relative import statements in config files, so that they:
+    1. locate files purely based on relative location, regardless of packages.
+       e.g. you can import file without having __init__
+    2. do not cache modules globally; modifications of module states has no side effect
+    3. support other storage system through PathManager, so config files can be in the cloud
+    4. imported dict are turned into omegaconf.DictConfig automatically
+    """
+    old_import = builtins.__import__
+
+    def find_relative_file(original_file, relative_import_path, level):
+        # NOTE: "from . import x" is not handled. Because then it's unclear
+        # if such import should produce `x` as a python module or DictConfig.
+        # This can be discussed further if needed.
+        relative_import_err = """
+Relative import of directories is not allowed within config files.
+Within a config file, relative import can only import other config files.
+""".replace(
+            "\n", " "
+        )
+        if not len(relative_import_path):
+            raise ImportError(relative_import_err)
+
+        cur_file = os.path.dirname(original_file)
+        for _ in range(level - 1):
+            cur_file = os.path.dirname(cur_file)
+        cur_name = relative_import_path.lstrip(".")
+        for part in cur_name.split("."):
+            cur_file = os.path.join(cur_file, part)
+        if not cur_file.endswith(".py"):
+            cur_file += ".py"
+        if not PathManager.isfile(cur_file):
+            cur_file_no_suffix = cur_file[: -len(".py")]
+            if PathManager.isdir(cur_file_no_suffix):
+                raise ImportError(f"Cannot import from {cur_file_no_suffix}." + relative_import_err)
+            else:
+                raise ImportError(
+                    f"Cannot import name {relative_import_path} from "
+                    f"{original_file}: {cur_file} does not exist."
+                )
+        return cur_file
+
+    def new_import(name, globals=None, locals=None, fromlist=(), level=0):
+        if (
+            # Only deal with relative imports inside config files
+            level != 0
+            and globals is not None
+            and (globals.get("__package__", "") or "").startswith(_CFG_PACKAGE_NAME)
+        ):
+            cur_file = find_relative_file(globals["__file__"], name, level)
+            _validate_py_syntax(cur_file)
+            spec = importlib.machinery.ModuleSpec(
+                _random_package_name(cur_file), None, origin=cur_file
+            )
+            module = importlib.util.module_from_spec(spec)
+            module.__file__ = cur_file
+            with PathManager.open(cur_file) as f:
+                content = f.read()
+            exec(compile(content, cur_file, "exec"), module.__dict__)
+            for name in fromlist:  # turn imported dict into DictConfig automatically
+                val = _cast_to_config(module.__dict__[name])
+                module.__dict__[name] = val
+            return module
+        return old_import(name, globals, locals, fromlist=fromlist, level=level)
+
+    builtins.__import__ = new_import
+    yield new_import
+    builtins.__import__ = old_import
+
+
+class LazyConfig:
+    """
+    Provide methods to save, load, and overrides an omegaconf config object
+    which may contain definition of lazily-constructed objects.
+    """
+
+    @staticmethod
+    def load_rel(filename: str, keys: Union[None, str, Tuple[str, ...]] = None):
+        """
+        Similar to :meth:`load()`, but load path relative to the caller's
+        source file.
+
+        This has the same functionality as a relative import, except that this method
+        accepts filename as a string, so more characters are allowed in the filename.
+        """
+        caller_frame = inspect.stack()[1]
+        caller_fname = caller_frame[0].f_code.co_filename
+        assert caller_fname != "<string>", "load_rel Unable to find caller"
+        caller_dir = os.path.dirname(caller_fname)
+        filename = os.path.join(caller_dir, filename)
+        return LazyConfig.load(filename, keys)
+
+    @staticmethod
+    def load(filename: str, keys: Union[None, str, Tuple[str, ...]] = None):
+        """
+        Load a config file.
+
+        Args:
+            filename: absolute path or relative path w.r.t. the current working directory
+            keys: keys to load and return. If not given, return all keys
+                (whose values are config objects) in a dict.
+        """
+        has_keys = keys is not None
+        filename = filename.replace("/./", "/")  # redundant
+        if os.path.splitext(filename)[1] not in [".py", ".yaml", ".yml"]:
+            raise ValueError(f"Config file {filename} has to be a python or yaml file.")
+        if filename.endswith(".py"):
+            _validate_py_syntax(filename)
+
+            with _patch_import():
+                # Record the filename
+                module_namespace = {
+                    "__file__": filename,
+                    "__package__": _random_package_name(filename),
+                }
+                with PathManager.open(filename) as f:
+                    content = f.read()
+                # Compile first with filename to:
+                # 1. make filename appears in stacktrace
+                # 2. make load_rel able to find its parent's (possibly remote) location
+                exec(compile(content, filename, "exec"), module_namespace)
+
+            ret = module_namespace
+        else:
+            with PathManager.open(filename) as f:
+                obj = yaml.unsafe_load(f)
+            ret = OmegaConf.create(obj, flags={"allow_objects": True})
+
+        if has_keys:
+            if isinstance(keys, str):
+                return _cast_to_config(ret[keys])
+            else:
+                return tuple(_cast_to_config(ret[a]) for a in keys)
+        else:
+            if filename.endswith(".py"):
+                # when not specified, only load those that are config objects
+                ret = DictConfig(
+                    {
+                        name: _cast_to_config(value)
+                        for name, value in ret.items()
+                        if isinstance(value, (DictConfig, ListConfig, dict))
+                        and not name.startswith("_")
+                    },
+                    flags={"allow_objects": True},
+                )
+            return ret
+
+    @staticmethod
+    def save(cfg, filename: str):
+        """
+        Save a config object to a yaml file.
+        Note that when the config dictionary contains complex objects (e.g. lambda),
+        it can't be saved to yaml. In that case we will print an error and
+        attempt to save to a pkl file instead.
+
+        Args:
+            cfg: an omegaconf config object
+            filename: yaml file name to save the config file
+        """
+        logger = logging.getLogger(__name__)
+        try:
+            cfg = deepcopy(cfg)
+        except Exception:
+            pass
+        else:
+            # if it's deep-copyable, then...
+            def _replace_type_by_name(x):
+                if "_target_" in x and callable(x._target_):
+                    try:
+                        x._target_ = _convert_target_to_string(x._target_)
+                    except AttributeError:
+                        pass
+
+            # not necessary, but makes yaml looks nicer
+            _visit_dict_config(cfg, _replace_type_by_name)
+
+        save_pkl = False
+        try:
+            dict = OmegaConf.to_container(
+                cfg,
+                # Do not resolve interpolation when saving, i.e. do not turn ${a} into
+                # actual values when saving.
+                resolve=False,
+                # Save structures (dataclasses) in a format that can be instantiated later.
+                # Without this option, the type information of the dataclass will be erased.
+                structured_config_mode=SCMode.INSTANTIATE,
+            )
+            dumped = yaml.dump(dict, default_flow_style=None, allow_unicode=True, width=9999)
+            with PathManager.open(filename, "w") as f:
+                f.write(dumped)
+
+            try:
+                _ = yaml.unsafe_load(dumped)  # test that it is loadable
+            except Exception:
+                logger.warning(
+                    "The config contains objects that cannot serialize to a valid yaml. "
+                    f"{filename} is human-readable but cannot be loaded."
+                )
+                save_pkl = True
+        except Exception:
+            logger.exception("Unable to serialize the config to yaml. Error:")
+            save_pkl = True
+
+        if save_pkl:
+            new_filename = filename + ".pkl"
+            try:
+                # retry by pickle
+                with PathManager.open(new_filename, "wb") as f:
+                    cloudpickle.dump(cfg, f)
+                logger.warning(f"Config is saved using cloudpickle at {new_filename}.")
+            except Exception:
+                pass
+
+    @staticmethod
+    def apply_overrides(cfg, overrides: List[str]):
+        """
+        In-place override contents of cfg.
+
+        Args:
+            cfg: an omegaconf config object
+            overrides: list of strings in the format of "a=b" to override configs.
+                See https://hydra.cc/docs/next/advanced/override_grammar/basic/
+                for syntax.
+
+        Returns:
+            the cfg object
+        """
+
+        def safe_update(cfg, key, value):
+            parts = key.split(".")
+            for idx in range(1, len(parts)):
+                prefix = ".".join(parts[:idx])
+                v = OmegaConf.select(cfg, prefix, default=None)
+                if v is None:
+                    break
+                if not OmegaConf.is_config(v):
+                    raise KeyError(
+                        f"Trying to update key {key}, but {prefix} "
+                        f"is not a config, but has type {type(v)}."
+                    )
+            OmegaConf.update(cfg, key, value, merge=True)
+
+        try:
+            from hydra.core.override_parser.overrides_parser import OverridesParser
+
+            has_hydra = True
+        except ImportError:
+            has_hydra = False
+
+        if has_hydra:
+            parser = OverridesParser.create()
+            overrides = parser.parse_overrides(overrides)
+            for o in overrides:
+                key = o.key_or_group
+                value = o.value()
+                if o.is_delete():
+                    # TODO support this
+                    raise NotImplementedError("deletion is not yet a supported override")
+                safe_update(cfg, key, value)
+        else:
+            # Fallback. Does not support all the features and error checking like hydra.
+            for o in overrides:
+                key, value = o.split("=")
+                try:
+                    value = ast.literal_eval(value)
+                except NameError:
+                    pass
+                safe_update(cfg, key, value)
+        return cfg
+
+    @staticmethod
+    def to_py(cfg, prefix: str = "cfg."):
+        """
+        Try to convert a config object into Python-like psuedo code.
+
+        Note that perfect conversion is not always possible. So the returned
+        results are mainly meant to be human-readable, and not meant to be executed.
+
+        Args:
+            cfg: an omegaconf config object
+            prefix: root name for the resulting code (default: "cfg.")
+
+
+        Returns:
+            str of formatted Python code
+        """
+        import black
+
+        cfg = OmegaConf.to_container(cfg, resolve=True)
+
+        def _to_str(obj, prefix=None, inside_call=False):
+            if prefix is None:
+                prefix = []
+            if isinstance(obj, abc.Mapping) and "_target_" in obj:
+                # Dict representing a function call
+                target = _convert_target_to_string(obj.pop("_target_"))
+                args = []
+                for k, v in sorted(obj.items()):
+                    args.append(f"{k}={_to_str(v, inside_call=True)}")
+                args = ", ".join(args)
+                call = f"{target}({args})"
+                return "".join(prefix) + call
+            elif isinstance(obj, abc.Mapping) and not inside_call:
+                # Dict that is not inside a call is a list of top-level config objects that we
+                # render as one object per line with dot separated prefixes
+                key_list = []
+                for k, v in sorted(obj.items()):
+                    if isinstance(v, abc.Mapping) and "_target_" not in v:
+                        key_list.append(_to_str(v, prefix=prefix + [k + "."]))
+                    else:
+                        key = "".join(prefix) + k
+                        key_list.append(f"{key}={_to_str(v)}")
+                return "\n".join(key_list)
+            elif isinstance(obj, abc.Mapping):
+                # Dict that is inside a call is rendered as a regular dict
+                return (
+                    "{"
+                    + ",".join(
+                        f"{repr(k)}: {_to_str(v, inside_call=inside_call)}"
+                        for k, v in sorted(obj.items())
+                    )
+                    + "}"
+                )
+            elif isinstance(obj, list):
+                return "[" + ",".join(_to_str(x, inside_call=inside_call) for x in obj) + "]"
+            else:
+                return repr(obj)
+
+        py_str = _to_str(cfg, prefix=[prefix])
+        try:
+            return black.format_str(py_str, mode=black.Mode())
+        except black.InvalidInput:
+            return py_str

detectron2/data/__init__.py

@@ -0,0 +1,19 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from . import transforms  # isort:skip
+
+from .build import (
+    build_batch_data_loader,
+    build_detection_test_loader,
+    build_detection_train_loader,
+    get_detection_dataset_dicts,
+    load_proposals_into_dataset,
+    print_instances_class_histogram,
+)
+from .catalog import DatasetCatalog, MetadataCatalog, Metadata
+from .common import DatasetFromList, MapDataset, ToIterableDataset
+from .dataset_mapper import DatasetMapper
+
+# ensure the builtin datasets are registered
+from . import datasets, samplers  # isort:skip
+
+__all__ = [k for k in globals().keys() if not k.startswith("_")]

detectron2/data/benchmark.py

@@ -0,0 +1,225 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import logging
+import numpy as np
+from itertools import count
+from typing import List, Tuple
+import torch
+import tqdm
+from fvcore.common.timer import Timer
+
+from detectron2.utils import comm
+
+from .build import build_batch_data_loader
+from .common import DatasetFromList, MapDataset
+from .samplers import TrainingSampler
+
+logger = logging.getLogger(__name__)
+
+
+class _EmptyMapDataset(torch.utils.data.Dataset):
+    """
+    Map anything to emptiness.
+    """
+
+    def __init__(self, dataset):
+        self.ds = dataset
+
+    def __len__(self):
+        return len(self.ds)
+
+    def __getitem__(self, idx):
+        _ = self.ds[idx]
+        return [0]
+
+
+def iter_benchmark(
+    iterator, num_iter: int, warmup: int = 5, max_time_seconds: float = 60
+) -> Tuple[float, List[float]]:
+    """
+    Benchmark an iterator/iterable for `num_iter` iterations with an extra
+    `warmup` iterations of warmup.
+    End early if `max_time_seconds` time is spent on iterations.
+
+    Returns:
+        float: average time (seconds) per iteration
+        list[float]: time spent on each iteration. Sometimes useful for further analysis.
+    """
+    num_iter, warmup = int(num_iter), int(warmup)
+
+    iterator = iter(iterator)
+    for _ in range(warmup):
+        next(iterator)
+    timer = Timer()
+    all_times = []
+    for curr_iter in tqdm.trange(num_iter):
+        start = timer.seconds()
+        if start > max_time_seconds:
+            num_iter = curr_iter
+            break
+        next(iterator)
+        all_times.append(timer.seconds() - start)
+    avg = timer.seconds() / num_iter
+    return avg, all_times
+
+
+class DataLoaderBenchmark:
+    """
+    Some common benchmarks that help understand perf bottleneck of a standard dataloader
+    made of dataset, mapper and sampler.
+    """
+
+    def __init__(
+        self,
+        dataset,
+        *,
+        mapper,
+        sampler=None,
+        total_batch_size,
+        num_workers=0,
+        max_time_seconds: int = 90,
+    ):
+        """
+        Args:
+            max_time_seconds (int): maximum time to spent for each benchmark
+            other args: same as in `build.py:build_detection_train_loader`
+        """
+        if isinstance(dataset, list):
+            dataset = DatasetFromList(dataset, copy=False, serialize=True)
+        if sampler is None:
+            sampler = TrainingSampler(len(dataset))
+
+        self.dataset = dataset
+        self.mapper = mapper
+        self.sampler = sampler
+        self.total_batch_size = total_batch_size
+        self.num_workers = num_workers
+        self.per_gpu_batch_size = self.total_batch_size // comm.get_world_size()
+
+        self.max_time_seconds = max_time_seconds
+
+    def _benchmark(self, iterator, num_iter, warmup, msg=None):
+        avg, all_times = iter_benchmark(iterator, num_iter, warmup, self.max_time_seconds)
+        if msg is not None:
+            self._log_time(msg, avg, all_times)
+        return avg, all_times
+
+    def _log_time(self, msg, avg, all_times, distributed=False):
+        percentiles = [np.percentile(all_times, k, interpolation="nearest") for k in [1, 5, 95, 99]]
+        if not distributed:
+            logger.info(
+                f"{msg}: avg={1.0/avg:.1f} it/s, "
+                f"p1={percentiles[0]:.2g}s, p5={percentiles[1]:.2g}s, "
+                f"p95={percentiles[2]:.2g}s, p99={percentiles[3]:.2g}s."
+            )
+            return
+        avg_per_gpu = comm.all_gather(avg)
+        percentiles_per_gpu = comm.all_gather(percentiles)
+        if comm.get_rank() > 0:
+            return
+        for idx, avg, percentiles in zip(count(), avg_per_gpu, percentiles_per_gpu):
+            logger.info(
+                f"GPU{idx} {msg}: avg={1.0/avg:.1f} it/s, "
+                f"p1={percentiles[0]:.2g}s, p5={percentiles[1]:.2g}s, "
+                f"p95={percentiles[2]:.2g}s, p99={percentiles[3]:.2g}s."
+            )
+
+    def benchmark_dataset(self, num_iter, warmup=5):
+        """
+        Benchmark the speed of taking raw samples from the dataset.
+        """
+
+        def loader():
+            while True:
+                for k in self.sampler:
+                    yield self.dataset[k]
+
+        self._benchmark(loader(), num_iter, warmup, "Dataset Alone")
+
+    def benchmark_mapper(self, num_iter, warmup=5):
+        """
+        Benchmark the speed of taking raw samples from the dataset and map
+        them in a single process.
+        """
+
+        def loader():
+            while True:
+                for k in self.sampler:
+                    yield self.mapper(self.dataset[k])
+
+        self._benchmark(loader(), num_iter, warmup, "Single Process Mapper (sec/sample)")
+
+    def benchmark_workers(self, num_iter, warmup=10):
+        """
+        Benchmark the dataloader by tuning num_workers to [0, 1, self.num_workers].
+        """
+        candidates = [0, 1]
+        if self.num_workers not in candidates:
+            candidates.append(self.num_workers)
+
+        dataset = MapDataset(self.dataset, self.mapper)
+        for n in candidates:
+            loader = build_batch_data_loader(
+                dataset,
+                self.sampler,
+                self.total_batch_size,
+                num_workers=n,
+            )
+            self._benchmark(
+                iter(loader),
+                num_iter * max(n, 1),
+                warmup * max(n, 1),
+                f"DataLoader ({n} workers, bs={self.per_gpu_batch_size})",
+            )
+            del loader
+
+    def benchmark_IPC(self, num_iter, warmup=10):
+        """
+        Benchmark the dataloader where each worker outputs nothing. This
+        eliminates the IPC overhead compared to the regular dataloader.
+
+        PyTorch multiprocessing's IPC only optimizes for torch tensors.
+        Large numpy arrays or other data structure may incur large IPC overhead.
+        """
+        n = self.num_workers
+        dataset = _EmptyMapDataset(MapDataset(self.dataset, self.mapper))
+        loader = build_batch_data_loader(
+            dataset, self.sampler, self.total_batch_size, num_workers=n
+        )
+        self._benchmark(
+            iter(loader),
+            num_iter * max(n, 1),
+            warmup * max(n, 1),
+            f"DataLoader ({n} workers, bs={self.per_gpu_batch_size}) w/o comm",
+        )
+
+    def benchmark_distributed(self, num_iter, warmup=10):
+        """
+        Benchmark the dataloader in each distributed worker, and log results of
+        all workers. This helps understand the final performance as well as
+        the variances among workers.
+
+        It also prints startup time (first iter) of the dataloader.
+        """
+        gpu = comm.get_world_size()
+        dataset = MapDataset(self.dataset, self.mapper)
+        n = self.num_workers
+        loader = build_batch_data_loader(
+            dataset, self.sampler, self.total_batch_size, num_workers=n
+        )
+
+        timer = Timer()
+        loader = iter(loader)
+        next(loader)
+        startup_time = timer.seconds()
+        logger.info("Dataloader startup time: {:.2f} seconds".format(startup_time))
+
+        comm.synchronize()
+
+        avg, all_times = self._benchmark(loader, num_iter * max(n, 1), warmup * max(n, 1))
+        del loader
+        self._log_time(
+            f"DataLoader ({gpu} GPUs x {n} workers, total bs={self.total_batch_size})",
+            avg,
+            all_times,
+            True,
+        )

detectron2/data/build.py

@@ -0,0 +1,694 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import itertools
+import logging
+import numpy as np
+import operator
+import pickle
+from collections import OrderedDict, defaultdict
+from typing import Any, Callable, Dict, List, Optional, Union
+import torch
+import torch.utils.data as torchdata
+from tabulate import tabulate
+from termcolor import colored
+
+from detectron2.config import configurable
+from detectron2.structures import BoxMode
+from detectron2.utils.comm import get_world_size
+from detectron2.utils.env import seed_all_rng
+from detectron2.utils.file_io import PathManager
+from detectron2.utils.logger import _log_api_usage, log_first_n
+
+from .catalog import DatasetCatalog, MetadataCatalog
+from .common import AspectRatioGroupedDataset, DatasetFromList, MapDataset, ToIterableDataset
+from .dataset_mapper import DatasetMapper
+from .detection_utils import check_metadata_consistency
+from .samplers import (
+    InferenceSampler,
+    RandomSubsetTrainingSampler,
+    RepeatFactorTrainingSampler,
+    TrainingSampler,
+)
+
+"""
+This file contains the default logic to build a dataloader for training or testing.
+"""
+
+__all__ = [
+    "build_batch_data_loader",
+    "build_detection_train_loader",
+    "build_detection_test_loader",
+    "get_detection_dataset_dicts",
+    "load_proposals_into_dataset",
+    "print_instances_class_histogram",
+]
+
+
+def filter_images_with_only_crowd_annotations(dataset_dicts):
+    """
+    Filter out images with none annotations or only crowd annotations
+    (i.e., images without non-crowd annotations).
+    A common training-time preprocessing on COCO dataset.
+
+    Args:
+        dataset_dicts (list[dict]): annotations in Detectron2 Dataset format.
+
+    Returns:
+        list[dict]: the same format, but filtered.
+    """
+    num_before = len(dataset_dicts)
+
+    def valid(anns):
+        for ann in anns:
+            if ann.get("iscrowd", 0) == 0:
+                return True
+        return False
+
+    dataset_dicts = [x for x in dataset_dicts if valid(x["annotations"])]
+    num_after = len(dataset_dicts)
+    logger = logging.getLogger(__name__)
+    logger.info(
+        "Removed {} images with no usable annotations. {} images left.".format(
+            num_before - num_after, num_after
+        )
+    )
+    return dataset_dicts
+
+
+def filter_images_with_few_keypoints(dataset_dicts, min_keypoints_per_image):
+    """
+    Filter out images with too few number of keypoints.
+
+    Args:
+        dataset_dicts (list[dict]): annotations in Detectron2 Dataset format.
+
+    Returns:
+        list[dict]: the same format as dataset_dicts, but filtered.
+    """
+    num_before = len(dataset_dicts)
+
+    def visible_keypoints_in_image(dic):
+        # Each keypoints field has the format [x1, y1, v1, ...], where v is visibility
+        annotations = dic["annotations"]
+        return sum(
+            (np.array(ann["keypoints"][2::3]) > 0).sum()
+            for ann in annotations
+            if "keypoints" in ann
+        )
+
+    dataset_dicts = [
+        x for x in dataset_dicts if visible_keypoints_in_image(x) >= min_keypoints_per_image
+    ]
+    num_after = len(dataset_dicts)
+    logger = logging.getLogger(__name__)
+    logger.info(
+        "Removed {} images with fewer than {} keypoints.".format(
+            num_before - num_after, min_keypoints_per_image
+        )
+    )
+    return dataset_dicts
+
+
+def load_proposals_into_dataset(dataset_dicts, proposal_file):
+    """
+    Load precomputed object proposals into the dataset.
+
+    The proposal file should be a pickled dict with the following keys:
+
+    - "ids": list[int] or list[str], the image ids
+    - "boxes": list[np.ndarray], each is an Nx4 array of boxes corresponding to the image id
+    - "objectness_logits": list[np.ndarray], each is an N sized array of objectness scores
+      corresponding to the boxes.
+    - "bbox_mode": the BoxMode of the boxes array. Defaults to ``BoxMode.XYXY_ABS``.
+
+    Args:
+        dataset_dicts (list[dict]): annotations in Detectron2 Dataset format.
+        proposal_file (str): file path of pre-computed proposals, in pkl format.
+
+    Returns:
+        list[dict]: the same format as dataset_dicts, but added proposal field.
+    """
+    logger = logging.getLogger(__name__)
+    logger.info("Loading proposals from: {}".format(proposal_file))
+
+    with PathManager.open(proposal_file, "rb") as f:
+        proposals = pickle.load(f, encoding="latin1")
+
+    # Rename the key names in D1 proposal files
+    rename_keys = {"indexes": "ids", "scores": "objectness_logits"}
+    for key in rename_keys:
+        if key in proposals:
+            proposals[rename_keys[key]] = proposals.pop(key)
+
+    # Fetch the indexes of all proposals that are in the dataset
+    # Convert image_id to str since they could be int.
+    img_ids = set({str(record["image_id"]) for record in dataset_dicts})
+    id_to_index = {str(id): i for i, id in enumerate(proposals["ids"]) if str(id) in img_ids}
+
+    # Assuming default bbox_mode of precomputed proposals are 'XYXY_ABS'
+    bbox_mode = BoxMode(proposals["bbox_mode"]) if "bbox_mode" in proposals else BoxMode.XYXY_ABS
+
+    for record in dataset_dicts:
+        # Get the index of the proposal
+        i = id_to_index[str(record["image_id"])]
+
+        boxes = proposals["boxes"][i]
+        objectness_logits = proposals["objectness_logits"][i]
+        # Sort the proposals in descending order of the scores
+        inds = objectness_logits.argsort()[::-1]
+        record["proposal_boxes"] = boxes[inds]
+        record["proposal_objectness_logits"] = objectness_logits[inds]
+        record["proposal_bbox_mode"] = bbox_mode
+
+    return dataset_dicts
+
+
+def print_instances_class_histogram(dataset_dicts, class_names):
+    """
+    Args:
+        dataset_dicts (list[dict]): list of dataset dicts.
+        class_names (list[str]): list of class names (zero-indexed).
+    """
+    num_classes = len(class_names)
+    hist_bins = np.arange(num_classes + 1)
+    histogram = np.zeros((num_classes,), dtype=int)
+    for entry in dataset_dicts:
+        annos = entry["annotations"]
+        classes = np.asarray(
+            [x["category_id"] for x in annos if not x.get("iscrowd", 0)], dtype=int
+        )
+        if len(classes):
+            assert classes.min() >= 0, f"Got an invalid category_id={classes.min()}"
+            assert (
+                classes.max() < num_classes
+            ), f"Got an invalid category_id={classes.max()} for a dataset of {num_classes} classes"
+        histogram += np.histogram(classes, bins=hist_bins)[0]
+
+    N_COLS = min(6, len(class_names) * 2)
+
+    def short_name(x):
+        # make long class names shorter. useful for lvis
+        if len(x) > 13:
+            return x[:11] + ".."
+        return x
+
+    data = list(
+        itertools.chain(*[[short_name(class_names[i]), int(v)] for i, v in enumerate(histogram)])
+    )
+    total_num_instances = sum(data[1::2])
+    data.extend([None] * (N_COLS - (len(data) % N_COLS)))
+    if num_classes > 1:
+        data.extend(["total", total_num_instances])
+    data = itertools.zip_longest(*[data[i::N_COLS] for i in range(N_COLS)])
+    table = tabulate(
+        data,
+        headers=["category", "#instances"] * (N_COLS // 2),
+        tablefmt="pipe",
+        numalign="left",
+        stralign="center",
+    )
+    log_first_n(
+        logging.INFO,
+        "Distribution of instances among all {} categories:\n".format(num_classes)
+        + colored(table, "cyan"),
+        key="message",
+    )
+
+
+def get_detection_dataset_dicts(
+    names,
+    filter_empty=True,
+    min_keypoints=0,
+    proposal_files=None,
+    check_consistency=True,
+):
+    """
+    Load and prepare dataset dicts for instance detection/segmentation and semantic segmentation.
+
+    Args:
+        names (str or list[str]): a dataset name or a list of dataset names
+        filter_empty (bool): whether to filter out images without instance annotations
+        min_keypoints (int): filter out images with fewer keypoints than
+            `min_keypoints`. Set to 0 to do nothing.
+        proposal_files (list[str]): if given, a list of object proposal files
+            that match each dataset in `names`.
+        check_consistency (bool): whether to check if datasets have consistent metadata.
+
+    Returns:
+        list[dict]: a list of dicts following the standard dataset dict format.
+    """
+    if isinstance(names, str):
+        names = [names]
+    assert len(names), names
+
+    available_datasets = DatasetCatalog.keys()
+    names_set = set(names)
+    if not names_set.issubset(available_datasets):
+        logger = logging.getLogger(__name__)
+        logger.warning(
+            "The following dataset names are not registered in the DatasetCatalog: "
+            f"{names_set - available_datasets}. "
+            f"Available datasets are {available_datasets}"
+        )
+
+    dataset_dicts = [DatasetCatalog.get(dataset_name) for dataset_name in names]
+
+    if isinstance(dataset_dicts[0], torchdata.Dataset):
+        if len(dataset_dicts) > 1:
+            # ConcatDataset does not work for iterable style dataset.
+            # We could support concat for iterable as well, but it's often
+            # not a good idea to concat iterables anyway.
+            return torchdata.ConcatDataset(dataset_dicts)
+        return dataset_dicts[0]
+
+    for dataset_name, dicts in zip(names, dataset_dicts):
+        assert len(dicts), "Dataset '{}' is empty!".format(dataset_name)
+
+    if proposal_files is not None:
+        assert len(names) == len(proposal_files)
+        # load precomputed proposals from proposal files
+        dataset_dicts = [
+            load_proposals_into_dataset(dataset_i_dicts, proposal_file)
+            for dataset_i_dicts, proposal_file in zip(dataset_dicts, proposal_files)
+        ]
+
+    dataset_dicts = list(itertools.chain.from_iterable(dataset_dicts))
+
+    has_instances = "annotations" in dataset_dicts[0]
+    if filter_empty and has_instances:
+        dataset_dicts = filter_images_with_only_crowd_annotations(dataset_dicts)
+    if min_keypoints > 0 and has_instances:
+        dataset_dicts = filter_images_with_few_keypoints(dataset_dicts, min_keypoints)
+
+    if check_consistency and has_instances:
+        try:
+            class_names = MetadataCatalog.get(names[0]).thing_classes
+            check_metadata_consistency("thing_classes", names)
+            print_instances_class_histogram(dataset_dicts, class_names)
+        except AttributeError:  # class names are not available for this dataset
+            pass
+
+    assert len(dataset_dicts), "No valid data found in {}.".format(",".join(names))
+    return dataset_dicts
+
+
+def build_batch_data_loader(
+    dataset,
+    sampler,
+    total_batch_size,
+    *,
+    aspect_ratio_grouping=False,
+    num_workers=0,
+    collate_fn=None,
+    drop_last: bool = True,
+    single_gpu_batch_size=None,
+    prefetch_factor=2,
+    persistent_workers=False,
+    pin_memory=False,
+    seed=None,
+    **kwargs,
+):
+    """
+    Build a batched dataloader. The main differences from `torch.utils.data.DataLoader` are:
+    1. support aspect ratio grouping options
+    2. use no "batch collation", because this is common for detection training
+
+    Args:
+        dataset (torch.utils.data.Dataset): a pytorch map-style or iterable dataset.
+        sampler (torch.utils.data.sampler.Sampler or None): a sampler that produces indices.
+            Must be provided iff. ``dataset`` is a map-style dataset.
+        total_batch_size, aspect_ratio_grouping, num_workers, collate_fn: see
+            :func:`build_detection_train_loader`.
+        single_gpu_batch_size: You can specify either `single_gpu_batch_size` or `total_batch_size`.
+            `single_gpu_batch_size` specifies the batch size that will be used for each gpu/process.
+            `total_batch_size` allows you to specify the total aggregate batch size across gpus.
+            It is an error to supply a value for both.
+        drop_last (bool): if ``True``, the dataloader will drop incomplete batches.
+
+    Returns:
+        iterable[list]. Length of each list is the batch size of the current
+            GPU. Each element in the list comes from the dataset.
+    """
+    if single_gpu_batch_size:
+        if total_batch_size:
+            raise ValueError(
+                """total_batch_size and single_gpu_batch_size are mutually incompatible.
+                Please specify only one. """
+            )
+        batch_size = single_gpu_batch_size
+    else:
+        world_size = get_world_size()
+        assert (
+            total_batch_size > 0 and total_batch_size % world_size == 0
+        ), "Total batch size ({}) must be divisible by the number of gpus ({}).".format(
+            total_batch_size, world_size
+        )
+        batch_size = total_batch_size // world_size
+    logger = logging.getLogger(__name__)
+    logger.info("Making batched data loader with batch_size=%d", batch_size)
+
+    if isinstance(dataset, torchdata.IterableDataset):
+        assert sampler is None, "sampler must be None if dataset is IterableDataset"
+    else:
+        dataset = ToIterableDataset(dataset, sampler, shard_chunk_size=batch_size)
+
+    generator = None
+    if seed is not None:
+        generator = torch.Generator()
+        generator.manual_seed(seed)
+
+    if aspect_ratio_grouping:
+        assert drop_last, "Aspect ratio grouping will drop incomplete batches."
+        data_loader = torchdata.DataLoader(
+            dataset,
+            num_workers=num_workers,
+            collate_fn=operator.itemgetter(0),  # don't batch, but yield individual elements
+            worker_init_fn=worker_init_reset_seed,
+            prefetch_factor=prefetch_factor if num_workers > 0 else None,
+            persistent_workers=persistent_workers,
+            pin_memory=pin_memory,
+            generator=generator,
+            **kwargs,
+        )  # yield individual mapped dict
+        data_loader = AspectRatioGroupedDataset(data_loader, batch_size)
+        if collate_fn is None:
+            return data_loader
+        return MapDataset(data_loader, collate_fn)
+    else:
+        return torchdata.DataLoader(
+            dataset,
+            batch_size=batch_size,
+            drop_last=drop_last,
+            num_workers=num_workers,
+            collate_fn=trivial_batch_collator if collate_fn is None else collate_fn,
+            worker_init_fn=worker_init_reset_seed,
+            prefetch_factor=prefetch_factor if num_workers > 0 else None,
+            persistent_workers=persistent_workers,
+            pin_memory=pin_memory,
+            generator=generator,
+            **kwargs,
+        )
+
+
+def _get_train_datasets_repeat_factors(cfg) -> Dict[str, float]:
+    repeat_factors = cfg.DATASETS.TRAIN_REPEAT_FACTOR
+    assert all(len(tup) == 2 for tup in repeat_factors)
+    name_to_weight = defaultdict(lambda: 1, dict(repeat_factors))
+    # The sampling weights map should only contain datasets in train config
+    unrecognized = set(name_to_weight.keys()) - set(cfg.DATASETS.TRAIN)
+    assert not unrecognized, f"unrecognized datasets: {unrecognized}"
+    logger = logging.getLogger(__name__)
+    logger.info(f"Found repeat factors: {list(name_to_weight.items())}")
+
+    # pyre-fixme[7]: Expected `Dict[str, float]` but got `DefaultDict[typing.Any, int]`.
+    return name_to_weight
+
+
+def _build_weighted_sampler(cfg, enable_category_balance=False):
+    dataset_repeat_factors = _get_train_datasets_repeat_factors(cfg)
+    # OrderedDict to guarantee order of values() consistent with repeat factors
+    dataset_name_to_dicts = OrderedDict(
+        {
+            name: get_detection_dataset_dicts(
+                [name],
+                filter_empty=cfg.DATALOADER.FILTER_EMPTY_ANNOTATIONS,
+                min_keypoints=(
+                    cfg.MODEL.ROI_KEYPOINT_HEAD.MIN_KEYPOINTS_PER_IMAGE
+                    if cfg.MODEL.KEYPOINT_ON
+                    else 0
+                ),
+                proposal_files=(
+                    cfg.DATASETS.PROPOSAL_FILES_TRAIN if cfg.MODEL.LOAD_PROPOSALS else None
+                ),
+            )
+            for name in cfg.DATASETS.TRAIN
+        }
+    )
+    # Repeat factor for every sample in the dataset
+    repeat_factors = [
+        [dataset_repeat_factors[dsname]] * len(dataset_name_to_dicts[dsname])
+        for dsname in cfg.DATASETS.TRAIN
+    ]
+
+    repeat_factors = list(itertools.chain.from_iterable(repeat_factors))
+
+    repeat_factors = torch.tensor(repeat_factors)
+    logger = logging.getLogger(__name__)
+    if enable_category_balance:
+        """
+        1. Calculate repeat factors using category frequency for each dataset and then merge them.
+        2. Element wise dot producting the dataset frequency repeat factors with
+            the category frequency repeat factors gives the final repeat factors.
+        """
+        category_repeat_factors = [
+            RepeatFactorTrainingSampler.repeat_factors_from_category_frequency(
+                dataset_dict, cfg.DATALOADER.REPEAT_THRESHOLD, sqrt=cfg.DATALOADER.REPEAT_SQRT
+            )
+            for dataset_dict in dataset_name_to_dicts.values()
+        ]
+        # flatten the category repeat factors from all datasets
+        category_repeat_factors = list(itertools.chain.from_iterable(category_repeat_factors))
+        category_repeat_factors = torch.tensor(category_repeat_factors)
+        repeat_factors = torch.mul(category_repeat_factors, repeat_factors)
+        repeat_factors = repeat_factors / torch.min(repeat_factors)
+        logger.info(
+            "Using WeightedCategoryTrainingSampler with repeat_factors={}".format(
+                cfg.DATASETS.TRAIN_REPEAT_FACTOR
+            )
+        )
+    else:
+        logger.info(
+            "Using WeightedTrainingSampler with repeat_factors={}".format(
+                cfg.DATASETS.TRAIN_REPEAT_FACTOR
+            )
+        )
+
+    sampler = RepeatFactorTrainingSampler(repeat_factors)
+    return sampler
+
+
+def _train_loader_from_config(cfg, mapper=None, *, dataset=None, sampler=None):
+    if dataset is None:
+        dataset = get_detection_dataset_dicts(
+            cfg.DATASETS.TRAIN,
+            filter_empty=cfg.DATALOADER.FILTER_EMPTY_ANNOTATIONS,
+            min_keypoints=(
+                cfg.MODEL.ROI_KEYPOINT_HEAD.MIN_KEYPOINTS_PER_IMAGE if cfg.MODEL.KEYPOINT_ON else 0
+            ),
+            proposal_files=cfg.DATASETS.PROPOSAL_FILES_TRAIN if cfg.MODEL.LOAD_PROPOSALS else None,
+        )
+        _log_api_usage("dataset." + cfg.DATASETS.TRAIN[0])
+
+    if mapper is None:
+        mapper = DatasetMapper(cfg, True)
+
+    if sampler is None:
+        sampler_name = cfg.DATALOADER.SAMPLER_TRAIN
+        logger = logging.getLogger(__name__)
+        if isinstance(dataset, torchdata.IterableDataset):
+            logger.info("Not using any sampler since the dataset is IterableDataset.")
+            sampler = None
+        else:
+            logger.info("Using training sampler {}".format(sampler_name))
+            if sampler_name == "TrainingSampler":
+                sampler = TrainingSampler(len(dataset))
+            elif sampler_name == "RepeatFactorTrainingSampler":
+                repeat_factors = RepeatFactorTrainingSampler.repeat_factors_from_category_frequency(
+                    dataset, cfg.DATALOADER.REPEAT_THRESHOLD, sqrt=cfg.DATALOADER.REPEAT_SQRT
+                )
+                sampler = RepeatFactorTrainingSampler(repeat_factors, seed=cfg.SEED)
+            elif sampler_name == "RandomSubsetTrainingSampler":
+                sampler = RandomSubsetTrainingSampler(
+                    len(dataset), cfg.DATALOADER.RANDOM_SUBSET_RATIO
+                )
+            elif sampler_name == "WeightedTrainingSampler":
+                sampler = _build_weighted_sampler(cfg)
+            elif sampler_name == "WeightedCategoryTrainingSampler":
+                sampler = _build_weighted_sampler(cfg, enable_category_balance=True)
+            else:
+                raise ValueError("Unknown training sampler: {}".format(sampler_name))
+
+    return {
+        "dataset": dataset,
+        "sampler": sampler,
+        "mapper": mapper,
+        "total_batch_size": cfg.SOLVER.IMS_PER_BATCH,
+        "aspect_ratio_grouping": cfg.DATALOADER.ASPECT_RATIO_GROUPING,
+        "num_workers": cfg.DATALOADER.NUM_WORKERS,
+    }
+
+
+@configurable(from_config=_train_loader_from_config)
+def build_detection_train_loader(
+    dataset,
+    *,
+    mapper,
+    sampler=None,
+    total_batch_size,
+    aspect_ratio_grouping=True,
+    num_workers=0,
+    collate_fn=None,
+    **kwargs,
+):
+    """
+    Build a dataloader for object detection with some default features.
+
+    Args:
+        dataset (list or torch.utils.data.Dataset): a list of dataset dicts,
+            or a pytorch dataset (either map-style or iterable). It can be obtained
+            by using :func:`DatasetCatalog.get` or :func:`get_detection_dataset_dicts`.
+        mapper (callable): a callable which takes a sample (dict) from dataset and
+            returns the format to be consumed by the model.
+            When using cfg, the default choice is ``DatasetMapper(cfg, is_train=True)``.
+        sampler (torch.utils.data.sampler.Sampler or None): a sampler that produces
+            indices to be applied on ``dataset``.
+            If ``dataset`` is map-style, the default sampler is a :class:`TrainingSampler`,
+            which coordinates an infinite random shuffle sequence across all workers.
+            Sampler must be None if ``dataset`` is iterable.
+        total_batch_size (int): total batch size across all workers.
+        aspect_ratio_grouping (bool): whether to group images with similar
+            aspect ratio for efficiency. When enabled, it requires each
+            element in dataset be a dict with keys "width" and "height".
+        num_workers (int): number of parallel data loading workers
+        collate_fn: a function that determines how to do batching, same as the argument of
+            `torch.utils.data.DataLoader`. Defaults to do no collation and return a list of
+            data. No collation is OK for small batch size and simple data structures.
+            If your batch size is large and each sample contains too many small tensors,
+            it's more efficient to collate them in data loader.
+
+    Returns:
+        torch.utils.data.DataLoader:
+            a dataloader. Each output from it is a ``list[mapped_element]`` of length
+            ``total_batch_size / num_workers``, where ``mapped_element`` is produced
+            by the ``mapper``.
+    """
+    if isinstance(dataset, list):
+        dataset = DatasetFromList(dataset, copy=False)
+    if mapper is not None:
+        dataset = MapDataset(dataset, mapper)
+
+    if isinstance(dataset, torchdata.IterableDataset):
+        assert sampler is None, "sampler must be None if dataset is IterableDataset"
+    else:
+        if sampler is None:
+            sampler = TrainingSampler(len(dataset))
+        assert isinstance(sampler, torchdata.Sampler), f"Expect a Sampler but got {type(sampler)}"
+    return build_batch_data_loader(
+        dataset,
+        sampler,
+        total_batch_size,
+        aspect_ratio_grouping=aspect_ratio_grouping,
+        num_workers=num_workers,
+        collate_fn=collate_fn,
+        **kwargs,
+    )
+
+
+def _test_loader_from_config(cfg, dataset_name, mapper=None):
+    """
+    Uses the given `dataset_name` argument (instead of the names in cfg), because the
+    standard practice is to evaluate each test set individually (not combining them).
+    """
+    if isinstance(dataset_name, str):
+        dataset_name = [dataset_name]
+
+    dataset = get_detection_dataset_dicts(
+        dataset_name,
+        filter_empty=False,
+        proposal_files=(
+            [
+                cfg.DATASETS.PROPOSAL_FILES_TEST[list(cfg.DATASETS.TEST).index(x)]
+                for x in dataset_name
+            ]
+            if cfg.MODEL.LOAD_PROPOSALS
+            else None
+        ),
+    )
+    if mapper is None:
+        mapper = DatasetMapper(cfg, False)
+    return {
+        "dataset": dataset,
+        "mapper": mapper,
+        "num_workers": cfg.DATALOADER.NUM_WORKERS,
+        "sampler": (
+            InferenceSampler(len(dataset))
+            if not isinstance(dataset, torchdata.IterableDataset)
+            else None
+        ),
+    }
+
+
+@configurable(from_config=_test_loader_from_config)
+def build_detection_test_loader(
+    dataset: Union[List[Any], torchdata.Dataset],
+    *,
+    mapper: Callable[[Dict[str, Any]], Any],
+    sampler: Optional[torchdata.Sampler] = None,
+    batch_size: int = 1,
+    num_workers: int = 0,
+    collate_fn: Optional[Callable[[List[Any]], Any]] = None,
+) -> torchdata.DataLoader:
+    """
+    Similar to `build_detection_train_loader`, with default batch size = 1,
+    and sampler = :class:`InferenceSampler`. This sampler coordinates all workers
+    to produce the exact set of all samples.
+
+    Args:
+        dataset: a list of dataset dicts,
+            or a pytorch dataset (either map-style or iterable). They can be obtained
+            by using :func:`DatasetCatalog.get` or :func:`get_detection_dataset_dicts`.
+        mapper: a callable which takes a sample (dict) from dataset
+           and returns the format to be consumed by the model.
+           When using cfg, the default choice is ``DatasetMapper(cfg, is_train=False)``.
+        sampler: a sampler that produces
+            indices to be applied on ``dataset``. Default to :class:`InferenceSampler`,
+            which splits the dataset across all workers. Sampler must be None
+            if `dataset` is iterable.
+        batch_size: the batch size of the data loader to be created.
+            Default to 1 image per worker since this is the standard when reporting
+            inference time in papers.
+        num_workers: number of parallel data loading workers
+        collate_fn: same as the argument of `torch.utils.data.DataLoader`.
+            Defaults to do no collation and return a list of data.
+
+    Returns:
+        DataLoader: a torch DataLoader, that loads the given detection
+        dataset, with test-time transformation and batching.
+
+    Examples:
+    ::
+        data_loader = build_detection_test_loader(
+            DatasetRegistry.get("my_test"),
+            mapper=DatasetMapper(...))
+
+        # or, instantiate with a CfgNode:
+        data_loader = build_detection_test_loader(cfg, "my_test")
+    """
+    if isinstance(dataset, list):
+        dataset = DatasetFromList(dataset, copy=False)
+    if mapper is not None:
+        dataset = MapDataset(dataset, mapper)
+    if isinstance(dataset, torchdata.IterableDataset):
+        assert sampler is None, "sampler must be None if dataset is IterableDataset"
+    else:
+        if sampler is None:
+            sampler = InferenceSampler(len(dataset))
+    return torchdata.DataLoader(
+        dataset,
+        batch_size=batch_size,
+        sampler=sampler,
+        drop_last=False,
+        num_workers=num_workers,
+        collate_fn=trivial_batch_collator if collate_fn is None else collate_fn,
+    )
+
+
+def trivial_batch_collator(batch):
+    """
+    A batch collator that does nothing.
+    """
+    return batch
+
+
+def worker_init_reset_seed(worker_id):
+    initial_seed = torch.initial_seed() % 2**31
+    seed_all_rng(initial_seed + worker_id)

detectron2/data/catalog.py

@@ -0,0 +1,236 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import copy
+import logging
+import types
+from collections import UserDict
+from typing import List
+
+from detectron2.utils.logger import log_first_n
+
+__all__ = ["DatasetCatalog", "MetadataCatalog", "Metadata"]
+
+
+class _DatasetCatalog(UserDict):
+    """
+    A global dictionary that stores information about the datasets and how to obtain them.
+
+    It contains a mapping from strings
+    (which are names that identify a dataset, e.g. "coco_2014_train")
+    to a function which parses the dataset and returns the samples in the
+    format of `list[dict]`.
+
+    The returned dicts should be in Detectron2 Dataset format (See DATASETS.md for details)
+    if used with the data loader functionalities in `data/build.py,data/detection_transform.py`.
+
+    The purpose of having this catalog is to make it easy to choose
+    different datasets, by just using the strings in the config.
+    """
+
+    def register(self, name, func):
+        """
+        Args:
+            name (str): the name that identifies a dataset, e.g. "coco_2014_train".
+            func (callable): a callable which takes no arguments and returns a list of dicts.
+                It must return the same results if called multiple times.
+        """
+        assert callable(func), "You must register a function with `DatasetCatalog.register`!"
+        assert name not in self, "Dataset '{}' is already registered!".format(name)
+        self[name] = func
+
+    def get(self, name):
+        """
+        Call the registered function and return its results.
+
+        Args:
+            name (str): the name that identifies a dataset, e.g. "coco_2014_train".
+
+        Returns:
+            list[dict]: dataset annotations.
+        """
+        try:
+            f = self[name]
+        except KeyError as e:
+            raise KeyError(
+                "Dataset '{}' is not registered! Available datasets are: {}".format(
+                    name, ", ".join(list(self.keys()))
+                )
+            ) from e
+        return f()
+
+    def list(self) -> List[str]:
+        """
+        List all registered datasets.
+
+        Returns:
+            list[str]
+        """
+        return list(self.keys())
+
+    def remove(self, name):
+        """
+        Alias of ``pop``.
+        """
+        self.pop(name)
+
+    def __str__(self):
+        return "DatasetCatalog(registered datasets: {})".format(", ".join(self.keys()))
+
+    __repr__ = __str__
+
+
+DatasetCatalog = _DatasetCatalog()
+DatasetCatalog.__doc__ = (
+    _DatasetCatalog.__doc__
+    + """
+    .. automethod:: detectron2.data.catalog.DatasetCatalog.register
+    .. automethod:: detectron2.data.catalog.DatasetCatalog.get
+"""
+)
+
+
+class Metadata(types.SimpleNamespace):
+    """
+    A class that supports simple attribute setter/getter.
+    It is intended for storing metadata of a dataset and make it accessible globally.
+
+    Examples:
+    ::
+        # somewhere when you load the data:
+        MetadataCatalog.get("mydataset").thing_classes = ["person", "dog"]
+
+        # somewhere when you print statistics or visualize:
+        classes = MetadataCatalog.get("mydataset").thing_classes
+    """
+
+    # the name of the dataset
+    # set default to N/A so that `self.name` in the errors will not trigger getattr again
+    name: str = "N/A"
+
+    _RENAMED = {
+        "class_names": "thing_classes",
+        "dataset_id_to_contiguous_id": "thing_dataset_id_to_contiguous_id",
+        "stuff_class_names": "stuff_classes",
+    }
+
+    def __getattr__(self, key):
+        if key in self._RENAMED:
+            log_first_n(
+                logging.WARNING,
+                "Metadata '{}' was renamed to '{}'!".format(key, self._RENAMED[key]),
+                n=10,
+            )
+            return getattr(self, self._RENAMED[key])
+
+        # "name" exists in every metadata
+        if len(self.__dict__) > 1:
+            raise AttributeError(
+                "Attribute '{}' does not exist in the metadata of dataset '{}'. Available "
+                "keys are {}.".format(key, self.name, str(self.__dict__.keys()))
+            )
+        else:
+            raise AttributeError(
+                f"Attribute '{key}' does not exist in the metadata of dataset '{self.name}': "
+                "metadata is empty."
+            )
+
+    def __setattr__(self, key, val):
+        if key in self._RENAMED:
+            log_first_n(
+                logging.WARNING,
+                "Metadata '{}' was renamed to '{}'!".format(key, self._RENAMED[key]),
+                n=10,
+            )
+            setattr(self, self._RENAMED[key], val)
+
+        # Ensure that metadata of the same name stays consistent
+        try:
+            oldval = getattr(self, key)
+            assert oldval == val, (
+                "Attribute '{}' in the metadata of '{}' cannot be set "
+                "to a different value!\n{} != {}".format(key, self.name, oldval, val)
+            )
+        except AttributeError:
+            super().__setattr__(key, val)
+
+    def as_dict(self):
+        """
+        Returns all the metadata as a dict.
+        Note that modifications to the returned dict will not reflect on the Metadata object.
+        """
+        return copy.copy(self.__dict__)
+
+    def set(self, **kwargs):
+        """
+        Set multiple metadata with kwargs.
+        """
+        for k, v in kwargs.items():
+            setattr(self, k, v)
+        return self
+
+    def get(self, key, default=None):
+        """
+        Access an attribute and return its value if exists.
+        Otherwise return default.
+        """
+        try:
+            return getattr(self, key)
+        except AttributeError:
+            return default
+
+
+class _MetadataCatalog(UserDict):
+    """
+    MetadataCatalog is a global dictionary that provides access to
+    :class:`Metadata` of a given dataset.
+
+    The metadata associated with a certain name is a singleton: once created, the
+    metadata will stay alive and will be returned by future calls to ``get(name)``.
+
+    It's like global variables, so don't abuse it.
+    It's meant for storing knowledge that's constant and shared across the execution
+    of the program, e.g.: the class names in COCO.
+    """
+
+    def get(self, name):
+        """
+        Args:
+            name (str): name of a dataset (e.g. coco_2014_train).
+
+        Returns:
+            Metadata: The :class:`Metadata` instance associated with this name,
+            or create an empty one if none is available.
+        """
+        assert len(name)
+        r = super().get(name, None)
+        if r is None:
+            r = self[name] = Metadata(name=name)
+        return r
+
+    def list(self):
+        """
+        List all registered metadata.
+
+        Returns:
+            list[str]: keys (names of datasets) of all registered metadata
+        """
+        return list(self.keys())
+
+    def remove(self, name):
+        """
+        Alias of ``pop``.
+        """
+        self.pop(name)
+
+    def __str__(self):
+        return "MetadataCatalog(registered metadata: {})".format(", ".join(self.keys()))
+
+    __repr__ = __str__
+
+
+MetadataCatalog = _MetadataCatalog()
+MetadataCatalog.__doc__ = (
+    _MetadataCatalog.__doc__
+    + """
+    .. automethod:: detectron2.data.catalog.MetadataCatalog.get
+"""
+)

detectron2/data/common.py

@@ -0,0 +1,339 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import contextlib
+import copy
+import itertools
+import logging
+import numpy as np
+import pickle
+import random
+from typing import Callable, Union
+import torch
+import torch.utils.data as data
+from torch.utils.data.sampler import Sampler
+
+from detectron2.utils.serialize import PicklableWrapper
+
+__all__ = ["MapDataset", "DatasetFromList", "AspectRatioGroupedDataset", "ToIterableDataset"]
+
+logger = logging.getLogger(__name__)
+
+
+# copied from: https://docs.python.org/3/library/itertools.html#recipes
+def _roundrobin(*iterables):
+    "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
+    # Recipe credited to George Sakkis
+    num_active = len(iterables)
+    nexts = itertools.cycle(iter(it).__next__ for it in iterables)
+    while num_active:
+        try:
+            for next in nexts:
+                yield next()
+        except StopIteration:
+            # Remove the iterator we just exhausted from the cycle.
+            num_active -= 1
+            nexts = itertools.cycle(itertools.islice(nexts, num_active))
+
+
+def _shard_iterator_dataloader_worker(iterable, chunk_size=1):
+    # Shard the iterable if we're currently inside pytorch dataloader worker.
+    worker_info = data.get_worker_info()
+    if worker_info is None or worker_info.num_workers == 1:
+        # do nothing
+        yield from iterable
+    else:
+        # worker0: 0, 1, ..., chunk_size-1, num_workers*chunk_size, num_workers*chunk_size+1, ...
+        # worker1: chunk_size, chunk_size+1, ...
+        # worker2: 2*chunk_size, 2*chunk_size+1, ...
+        # ...
+        yield from _roundrobin(
+            *[
+                itertools.islice(
+                    iterable,
+                    worker_info.id * chunk_size + chunk_i,
+                    None,
+                    worker_info.num_workers * chunk_size,
+                )
+                for chunk_i in range(chunk_size)
+            ]
+        )
+
+
+class _MapIterableDataset(data.IterableDataset):
+    """
+    Map a function over elements in an IterableDataset.
+
+    Similar to pytorch's MapIterDataPipe, but support filtering when map_func
+    returns None.
+
+    This class is not public-facing. Will be called by `MapDataset`.
+    """
+
+    def __init__(self, dataset, map_func):
+        self._dataset = dataset
+        self._map_func = PicklableWrapper(map_func)  # wrap so that a lambda will work
+
+    def __len__(self):
+        return len(self._dataset)
+
+    def __iter__(self):
+        for x in map(self._map_func, self._dataset):
+            if x is not None:
+                yield x
+
+
+class MapDataset(data.Dataset):
+    """
+    Map a function over the elements in a dataset.
+    """
+
+    def __init__(self, dataset, map_func):
+        """
+        Args:
+            dataset: a dataset where map function is applied. Can be either
+                map-style or iterable dataset. When given an iterable dataset,
+                the returned object will also be an iterable dataset.
+            map_func: a callable which maps the element in dataset. map_func can
+                return None to skip the data (e.g. in case of errors).
+                How None is handled depends on the style of `dataset`.
+                If `dataset` is map-style, it randomly tries other elements.
+                If `dataset` is iterable, it skips the data and tries the next.
+        """
+        self._dataset = dataset
+        self._map_func = PicklableWrapper(map_func)  # wrap so that a lambda will work
+
+        self._rng = random.Random(42)
+        self._fallback_candidates = set(range(len(dataset)))
+
+    def __new__(cls, dataset, map_func):
+        is_iterable = isinstance(dataset, data.IterableDataset)
+        if is_iterable:
+            return _MapIterableDataset(dataset, map_func)
+        else:
+            return super().__new__(cls)
+
+    def __getnewargs__(self):
+        return self._dataset, self._map_func
+
+    def __len__(self):
+        return len(self._dataset)
+
+    def __getitem__(self, idx):
+        retry_count = 0
+        cur_idx = int(idx)
+
+        while True:
+            data = self._map_func(self._dataset[cur_idx])
+            if data is not None:
+                self._fallback_candidates.add(cur_idx)
+                return data
+
+            # _map_func fails for this idx, use a random new index from the pool
+            retry_count += 1
+            self._fallback_candidates.discard(cur_idx)
+            cur_idx = self._rng.sample(self._fallback_candidates, k=1)[0]
+
+            if retry_count >= 3:
+                logger = logging.getLogger(__name__)
+                logger.warning(
+                    "Failed to apply `_map_func` for idx: {}, retry count: {}".format(
+                        idx, retry_count
+                    )
+                )
+
+
+class _TorchSerializedList:
+    """
+    A list-like object whose items are serialized and stored in a torch tensor. When
+    launching a process that uses TorchSerializedList with "fork" start method,
+    the subprocess can read the same buffer without triggering copy-on-access. When
+    launching a process that uses TorchSerializedList with "spawn/forkserver" start
+    method, the list will be pickled by a special ForkingPickler registered by PyTorch
+    that moves data to shared memory. In both cases, this allows parent and child
+    processes to share RAM for the list data, hence avoids the issue in
+    https://github.com/pytorch/pytorch/issues/13246.
+
+    See also https://ppwwyyxx.com/blog/2022/Demystify-RAM-Usage-in-Multiprocess-DataLoader/
+    on how it works.
+    """
+
+    def __init__(self, lst: list):
+        self._lst = lst
+
+        def _serialize(data):
+            buffer = pickle.dumps(data, protocol=-1)
+            return np.frombuffer(buffer, dtype=np.uint8)
+
+        logger.info(
+            "Serializing {} elements to byte tensors and concatenating them all ...".format(
+                len(self._lst)
+            )
+        )
+        self._lst = [_serialize(x) for x in self._lst]
+        self._addr = np.asarray([len(x) for x in self._lst], dtype=np.int64)
+        self._addr = torch.from_numpy(np.cumsum(self._addr))
+        self._lst = torch.from_numpy(np.concatenate(self._lst))
+        logger.info("Serialized dataset takes {:.2f} MiB".format(len(self._lst) / 1024**2))
+
+    def __len__(self):
+        return len(self._addr)
+
+    def __getitem__(self, idx):
+        start_addr = 0 if idx == 0 else self._addr[idx - 1].item()
+        end_addr = self._addr[idx].item()
+        bytes = memoryview(self._lst[start_addr:end_addr].numpy())
+
+        # @lint-ignore PYTHONPICKLEISBAD
+        return pickle.loads(bytes)
+
+
+_DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD = _TorchSerializedList
+
+
+@contextlib.contextmanager
+def set_default_dataset_from_list_serialize_method(new):
+    """
+    Context manager for using custom serialize function when creating DatasetFromList
+    """
+
+    global _DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD
+    orig = _DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD
+    _DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD = new
+    yield
+    _DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD = orig
+
+
+class DatasetFromList(data.Dataset):
+    """
+    Wrap a list to a torch Dataset. It produces elements of the list as data.
+    """
+
+    def __init__(
+        self,
+        lst: list,
+        copy: bool = True,
+        serialize: Union[bool, Callable] = True,
+    ):
+        """
+        Args:
+            lst (list): a list which contains elements to produce.
+            copy (bool): whether to deepcopy the element when producing it,
+                so that the result can be modified in place without affecting the
+                source in the list.
+            serialize (bool or callable): whether to serialize the stroage to other
+                backend. If `True`, the default serialize method will be used, if given
+                a callable, the callable will be used as serialize method.
+        """
+        self._lst = lst
+        self._copy = copy
+        if not isinstance(serialize, (bool, Callable)):
+            raise TypeError(f"Unsupported type for argument `serailzie`: {serialize}")
+        self._serialize = serialize is not False
+
+        if self._serialize:
+            serialize_method = (
+                serialize
+                if isinstance(serialize, Callable)
+                else _DEFAULT_DATASET_FROM_LIST_SERIALIZE_METHOD
+            )
+            logger.info(f"Serializing the dataset using: {serialize_method}")
+            self._lst = serialize_method(self._lst)
+
+    def __len__(self):
+        return len(self._lst)
+
+    def __getitem__(self, idx):
+        if self._copy and not self._serialize:
+            return copy.deepcopy(self._lst[idx])
+        else:
+            return self._lst[idx]
+
+
+class ToIterableDataset(data.IterableDataset):
+    """
+    Convert an old indices-based (also called map-style) dataset
+    to an iterable-style dataset.
+    """
+
+    def __init__(
+        self,
+        dataset: data.Dataset,
+        sampler: Sampler,
+        shard_sampler: bool = True,
+        shard_chunk_size: int = 1,
+    ):
+        """
+        Args:
+            dataset: an old-style dataset with ``__getitem__``
+            sampler: a cheap iterable that produces indices to be applied on ``dataset``.
+            shard_sampler: whether to shard the sampler based on the current pytorch data loader
+                worker id. When an IterableDataset is forked by pytorch's DataLoader into multiple
+                workers, it is responsible for sharding its data based on worker id so that workers
+                don't produce identical data.
+
+                Most samplers (like our TrainingSampler) do not shard based on dataloader worker id
+                and this argument should be set to True. But certain samplers may be already
+                sharded, in that case this argument should be set to False.
+            shard_chunk_size: when sharding the sampler, each worker will
+        """
+        assert not isinstance(dataset, data.IterableDataset), dataset
+        assert isinstance(sampler, Sampler), sampler
+        self.dataset = dataset
+        self.sampler = sampler
+        self.shard_sampler = shard_sampler
+        self.shard_chunk_size = shard_chunk_size
+
+    def __iter__(self):
+        if not self.shard_sampler:
+            sampler = self.sampler
+        else:
+            # With map-style dataset, `DataLoader(dataset, sampler)` runs the
+            # sampler in main process only. But `DataLoader(ToIterableDataset(dataset, sampler))`
+            # will run sampler in every of the N worker. So we should only keep 1/N of the ids on
+            # each worker. The assumption is that sampler is cheap to iterate so it's fine to
+            # discard ids in workers.
+            sampler = _shard_iterator_dataloader_worker(self.sampler, self.shard_chunk_size)
+        for idx in sampler:
+            yield self.dataset[idx]
+
+    def __len__(self):
+        return len(self.sampler)
+
+
+class AspectRatioGroupedDataset(data.IterableDataset):
+    """
+    Batch data that have similar aspect ratio together.
+    In this implementation, images whose aspect ratio < (or >) 1 will
+    be batched together.
+    This improves training speed because the images then need less padding
+    to form a batch.
+
+    It assumes the underlying dataset produces dicts with "width" and "height" keys.
+    It will then produce a list of original dicts with length = batch_size,
+    all with similar aspect ratios.
+    """
+
+    def __init__(self, dataset, batch_size):
+        """
+        Args:
+            dataset: an iterable. Each element must be a dict with keys
+                "width" and "height", which will be used to batch data.
+            batch_size (int):
+        """
+        self.dataset = dataset
+        self.batch_size = batch_size
+        self._buckets = [[] for _ in range(2)]
+        # Hard-coded two aspect ratio groups: w > h and w < h.
+        # Can add support for more aspect ratio groups, but doesn't seem useful
+
+    def __iter__(self):
+        for d in self.dataset:
+            w, h = d["width"], d["height"]
+            bucket_id = 0 if w > h else 1
+            bucket = self._buckets[bucket_id]
+            bucket.append(d)
+            if len(bucket) == self.batch_size:
+                data = bucket[:]
+                # Clear bucket first, because code after yield is not
+                # guaranteed to execute
+                del bucket[:]
+                yield data

detectron2/data/dataset_mapper.py

@@ -0,0 +1,191 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import copy
+import logging
+import numpy as np
+from typing import List, Optional, Union
+import torch
+
+from detectron2.config import configurable
+
+from . import detection_utils as utils
+from . import transforms as T
+
+"""
+This file contains the default mapping that's applied to "dataset dicts".
+"""
+
+__all__ = ["DatasetMapper"]
+
+
+class DatasetMapper:
+    """
+    A callable which takes a dataset dict in Detectron2 Dataset format,
+    and map it into a format used by the model.
+
+    This is the default callable to be used to map your dataset dict into training data.
+    You may need to follow it to implement your own one for customized logic,
+    such as a different way to read or transform images.
+    See :doc:`/tutorials/data_loading` for details.
+
+    The callable currently does the following:
+
+    1. Read the image from "file_name"
+    2. Applies cropping/geometric transforms to the image and annotations
+    3. Prepare data and annotations to Tensor and :class:`Instances`
+    """
+
+    @configurable
+    def __init__(
+        self,
+        is_train: bool,
+        *,
+        augmentations: List[Union[T.Augmentation, T.Transform]],
+        image_format: str,
+        use_instance_mask: bool = False,
+        use_keypoint: bool = False,
+        instance_mask_format: str = "polygon",
+        keypoint_hflip_indices: Optional[np.ndarray] = None,
+        precomputed_proposal_topk: Optional[int] = None,
+        recompute_boxes: bool = False,
+    ):
+        """
+        NOTE: this interface is experimental.
+
+        Args:
+            is_train: whether it's used in training or inference
+            augmentations: a list of augmentations or deterministic transforms to apply
+            image_format: an image format supported by :func:`detection_utils.read_image`.
+            use_instance_mask: whether to process instance segmentation annotations, if available
+            use_keypoint: whether to process keypoint annotations if available
+            instance_mask_format: one of "polygon" or "bitmask". Process instance segmentation
+                masks into this format.
+            keypoint_hflip_indices: see :func:`detection_utils.create_keypoint_hflip_indices`
+            precomputed_proposal_topk: if given, will load pre-computed
+                proposals from dataset_dict and keep the top k proposals for each image.
+            recompute_boxes: whether to overwrite bounding box annotations
+                by computing tight bounding boxes from instance mask annotations.
+        """
+        if recompute_boxes:
+            assert use_instance_mask, "recompute_boxes requires instance masks"
+        # fmt: off
+        self.is_train               = is_train
+        self.augmentations          = T.AugmentationList(augmentations)
+        self.image_format           = image_format
+        self.use_instance_mask      = use_instance_mask
+        self.instance_mask_format   = instance_mask_format
+        self.use_keypoint           = use_keypoint
+        self.keypoint_hflip_indices = keypoint_hflip_indices
+        self.proposal_topk          = precomputed_proposal_topk
+        self.recompute_boxes        = recompute_boxes
+        # fmt: on
+        logger = logging.getLogger(__name__)
+        mode = "training" if is_train else "inference"
+        logger.info(f"[DatasetMapper] Augmentations used in {mode}: {augmentations}")
+
+    @classmethod
+    def from_config(cls, cfg, is_train: bool = True):
+        augs = utils.build_augmentation(cfg, is_train)
+        if cfg.INPUT.CROP.ENABLED and is_train:
+            augs.insert(0, T.RandomCrop(cfg.INPUT.CROP.TYPE, cfg.INPUT.CROP.SIZE))
+            recompute_boxes = cfg.MODEL.MASK_ON
+        else:
+            recompute_boxes = False
+
+        ret = {
+            "is_train": is_train,
+            "augmentations": augs,
+            "image_format": cfg.INPUT.FORMAT,
+            "use_instance_mask": cfg.MODEL.MASK_ON,
+            "instance_mask_format": cfg.INPUT.MASK_FORMAT,
+            "use_keypoint": cfg.MODEL.KEYPOINT_ON,
+            "recompute_boxes": recompute_boxes,
+        }
+
+        if cfg.MODEL.KEYPOINT_ON:
+            ret["keypoint_hflip_indices"] = utils.create_keypoint_hflip_indices(cfg.DATASETS.TRAIN)
+
+        if cfg.MODEL.LOAD_PROPOSALS:
+            ret["precomputed_proposal_topk"] = (
+                cfg.DATASETS.PRECOMPUTED_PROPOSAL_TOPK_TRAIN
+                if is_train
+                else cfg.DATASETS.PRECOMPUTED_PROPOSAL_TOPK_TEST
+            )
+        return ret
+
+    def _transform_annotations(self, dataset_dict, transforms, image_shape):
+        # USER: Modify this if you want to keep them for some reason.
+        for anno in dataset_dict["annotations"]:
+            if not self.use_instance_mask:
+                anno.pop("segmentation", None)
+            if not self.use_keypoint:
+                anno.pop("keypoints", None)
+
+        # USER: Implement additional transformations if you have other types of data
+        annos = [
+            utils.transform_instance_annotations(
+                obj, transforms, image_shape, keypoint_hflip_indices=self.keypoint_hflip_indices
+            )
+            for obj in dataset_dict.pop("annotations")
+            if obj.get("iscrowd", 0) == 0
+        ]
+        instances = utils.annotations_to_instances(
+            annos, image_shape, mask_format=self.instance_mask_format
+        )
+
+        # After transforms such as cropping are applied, the bounding box may no longer
+        # tightly bound the object. As an example, imagine a triangle object
+        # [(0,0), (2,0), (0,2)] cropped by a box [(1,0),(2,2)] (XYXY format). The tight
+        # bounding box of the cropped triangle should be [(1,0),(2,1)], which is not equal to
+        # the intersection of original bounding box and the cropping box.
+        if self.recompute_boxes:
+            instances.gt_boxes = instances.gt_masks.get_bounding_boxes()
+        dataset_dict["instances"] = utils.filter_empty_instances(instances)
+
+    def __call__(self, dataset_dict):
+        """
+        Args:
+            dataset_dict (dict): Metadata of one image, in Detectron2 Dataset format.
+
+        Returns:
+            dict: a format that builtin models in detectron2 accept
+        """
+        dataset_dict = copy.deepcopy(dataset_dict)  # it will be modified by code below
+        # USER: Write your own image loading if it's not from a file
+        image = utils.read_image(dataset_dict["file_name"], format=self.image_format)
+        utils.check_image_size(dataset_dict, image)
+
+        # USER: Remove if you don't do semantic/panoptic segmentation.
+        if "sem_seg_file_name" in dataset_dict:
+            sem_seg_gt = utils.read_image(dataset_dict.pop("sem_seg_file_name"), "L").squeeze(2)
+        else:
+            sem_seg_gt = None
+
+        aug_input = T.AugInput(image, sem_seg=sem_seg_gt)
+        transforms = self.augmentations(aug_input)
+        image, sem_seg_gt = aug_input.image, aug_input.sem_seg
+
+        image_shape = image.shape[:2]  # h, w
+        # Pytorch's dataloader is efficient on torch.Tensor due to shared-memory,
+        # but not efficient on large generic data structures due to the use of pickle & mp.Queue.
+        # Therefore it's important to use torch.Tensor.
+        dataset_dict["image"] = torch.as_tensor(np.ascontiguousarray(image.transpose(2, 0, 1)))
+        if sem_seg_gt is not None:
+            dataset_dict["sem_seg"] = torch.as_tensor(sem_seg_gt.astype("long"))
+
+        # USER: Remove if you don't use pre-computed proposals.
+        # Most users would not need this feature.
+        if self.proposal_topk is not None:
+            utils.transform_proposals(
+                dataset_dict, image_shape, transforms, proposal_topk=self.proposal_topk
+            )
+
+        if not self.is_train:
+            # USER: Modify this if you want to keep them for some reason.
+            dataset_dict.pop("annotations", None)
+            dataset_dict.pop("sem_seg_file_name", None)
+            return dataset_dict
+
+        if "annotations" in dataset_dict:
+            self._transform_annotations(dataset_dict, transforms, image_shape)
+
+        return dataset_dict

detectron2/data/datasets/README.md

@@ -0,0 +1,9 @@
+
+
+### Common Datasets
+
+The dataset implemented here do not need to load the data into the final format.
+It should provide the minimal data structure needed to use the dataset, so it can be very efficient.
+
+For example, for an image dataset, just provide the file names and labels, but don't read the images.
+Let the downstream decide how to read.

detectron2/data/datasets/__init__.py

@@ -0,0 +1,9 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .coco import load_coco_json, load_sem_seg, register_coco_instances, convert_to_coco_json
+from .coco_panoptic import register_coco_panoptic, register_coco_panoptic_separated
+from .lvis import load_lvis_json, register_lvis_instances, get_lvis_instances_meta
+from .pascal_voc import load_voc_instances, register_pascal_voc
+from . import builtin as _builtin  # ensure the builtin datasets are registered
+
+
+__all__ = [k for k in globals().keys() if not k.startswith("_")]

detectron2/data/datasets/builtin.py

@@ -0,0 +1,259 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+
+"""
+This file registers pre-defined datasets at hard-coded paths, and their metadata.
+
+We hard-code metadata for common datasets. This will enable:
+1. Consistency check when loading the datasets
+2. Use models on these standard datasets directly and run demos,
+   without having to download the dataset annotations
+
+We hard-code some paths to the dataset that's assumed to
+exist in "./datasets/".
+
+Users SHOULD NOT use this file to create new dataset / metadata for new dataset.
+To add new dataset, refer to the tutorial "docs/DATASETS.md".
+"""
+
+import os
+
+from detectron2.data import DatasetCatalog, MetadataCatalog
+
+from .builtin_meta import ADE20K_SEM_SEG_CATEGORIES, _get_builtin_metadata
+from .cityscapes import load_cityscapes_instances, load_cityscapes_semantic
+from .cityscapes_panoptic import register_all_cityscapes_panoptic
+from .coco import load_sem_seg, register_coco_instances
+from .coco_panoptic import register_coco_panoptic, register_coco_panoptic_separated
+from .lvis import get_lvis_instances_meta, register_lvis_instances
+from .pascal_voc import register_pascal_voc
+
+# ==== Predefined datasets and splits for COCO ==========
+
+_PREDEFINED_SPLITS_COCO = {}
+_PREDEFINED_SPLITS_COCO["coco"] = {
+    "coco_2014_train": ("coco/train2014", "coco/annotations/instances_train2014.json"),
+    "coco_2014_val": ("coco/val2014", "coco/annotations/instances_val2014.json"),
+    "coco_2014_minival": ("coco/val2014", "coco/annotations/instances_minival2014.json"),
+    "coco_2014_valminusminival": (
+        "coco/val2014",
+        "coco/annotations/instances_valminusminival2014.json",
+    ),
+    "coco_2017_train": ("coco/train2017", "coco/annotations/instances_train2017.json"),
+    "coco_2017_val": ("coco/val2017", "coco/annotations/instances_val2017.json"),
+    "coco_2017_test": ("coco/test2017", "coco/annotations/image_info_test2017.json"),
+    "coco_2017_test-dev": ("coco/test2017", "coco/annotations/image_info_test-dev2017.json"),
+    "coco_2017_val_100": ("coco/val2017", "coco/annotations/instances_val2017_100.json"),
+}
+
+_PREDEFINED_SPLITS_COCO["coco_person"] = {
+    "keypoints_coco_2014_train": (
+        "coco/train2014",
+        "coco/annotations/person_keypoints_train2014.json",
+    ),
+    "keypoints_coco_2014_val": ("coco/val2014", "coco/annotations/person_keypoints_val2014.json"),
+    "keypoints_coco_2014_minival": (
+        "coco/val2014",
+        "coco/annotations/person_keypoints_minival2014.json",
+    ),
+    "keypoints_coco_2014_valminusminival": (
+        "coco/val2014",
+        "coco/annotations/person_keypoints_valminusminival2014.json",
+    ),
+    "keypoints_coco_2017_train": (
+        "coco/train2017",
+        "coco/annotations/person_keypoints_train2017.json",
+    ),
+    "keypoints_coco_2017_val": ("coco/val2017", "coco/annotations/person_keypoints_val2017.json"),
+    "keypoints_coco_2017_val_100": (
+        "coco/val2017",
+        "coco/annotations/person_keypoints_val2017_100.json",
+    ),
+}
+
+
+_PREDEFINED_SPLITS_COCO_PANOPTIC = {
+    "coco_2017_train_panoptic": (
+        # This is the original panoptic annotation directory
+        "coco/panoptic_train2017",
+        "coco/annotations/panoptic_train2017.json",
+        # This directory contains semantic annotations that are
+        # converted from panoptic annotations.
+        # It is used by PanopticFPN.
+        # You can use the script at detectron2/datasets/prepare_panoptic_fpn.py
+        # to create these directories.
+        "coco/panoptic_stuff_train2017",
+    ),
+    "coco_2017_val_panoptic": (
+        "coco/panoptic_val2017",
+        "coco/annotations/panoptic_val2017.json",
+        "coco/panoptic_stuff_val2017",
+    ),
+    "coco_2017_val_100_panoptic": (
+        "coco/panoptic_val2017_100",
+        "coco/annotations/panoptic_val2017_100.json",
+        "coco/panoptic_stuff_val2017_100",
+    ),
+}
+
+
+def register_all_coco(root):
+    for dataset_name, splits_per_dataset in _PREDEFINED_SPLITS_COCO.items():
+        for key, (image_root, json_file) in splits_per_dataset.items():
+            # Assume pre-defined datasets live in `./datasets`.
+            register_coco_instances(
+                key,
+                _get_builtin_metadata(dataset_name),
+                os.path.join(root, json_file) if "://" not in json_file else json_file,
+                os.path.join(root, image_root),
+            )
+
+    for (
+        prefix,
+        (panoptic_root, panoptic_json, semantic_root),
+    ) in _PREDEFINED_SPLITS_COCO_PANOPTIC.items():
+        prefix_instances = prefix[: -len("_panoptic")]
+        instances_meta = MetadataCatalog.get(prefix_instances)
+        image_root, instances_json = instances_meta.image_root, instances_meta.json_file
+        # The "separated" version of COCO panoptic segmentation dataset,
+        # e.g. used by Panoptic FPN
+        register_coco_panoptic_separated(
+            prefix,
+            _get_builtin_metadata("coco_panoptic_separated"),
+            image_root,
+            os.path.join(root, panoptic_root),
+            os.path.join(root, panoptic_json),
+            os.path.join(root, semantic_root),
+            instances_json,
+        )
+        # The "standard" version of COCO panoptic segmentation dataset,
+        # e.g. used by Panoptic-DeepLab
+        register_coco_panoptic(
+            prefix,
+            _get_builtin_metadata("coco_panoptic_standard"),
+            image_root,
+            os.path.join(root, panoptic_root),
+            os.path.join(root, panoptic_json),
+            instances_json,
+        )
+
+
+# ==== Predefined datasets and splits for LVIS ==========
+
+
+_PREDEFINED_SPLITS_LVIS = {
+    "lvis_v1": {
+        "lvis_v1_train": ("coco/", "lvis/lvis_v1_train.json"),
+        "lvis_v1_val": ("coco/", "lvis/lvis_v1_val.json"),
+        "lvis_v1_test_dev": ("coco/", "lvis/lvis_v1_image_info_test_dev.json"),
+        "lvis_v1_test_challenge": ("coco/", "lvis/lvis_v1_image_info_test_challenge.json"),
+    },
+    "lvis_v0.5": {
+        "lvis_v0.5_train": ("coco/", "lvis/lvis_v0.5_train.json"),
+        "lvis_v0.5_val": ("coco/", "lvis/lvis_v0.5_val.json"),
+        "lvis_v0.5_val_rand_100": ("coco/", "lvis/lvis_v0.5_val_rand_100.json"),
+        "lvis_v0.5_test": ("coco/", "lvis/lvis_v0.5_image_info_test.json"),
+    },
+    "lvis_v0.5_cocofied": {
+        "lvis_v0.5_train_cocofied": ("coco/", "lvis/lvis_v0.5_train_cocofied.json"),
+        "lvis_v0.5_val_cocofied": ("coco/", "lvis/lvis_v0.5_val_cocofied.json"),
+    },
+}
+
+
+def register_all_lvis(root):
+    for dataset_name, splits_per_dataset in _PREDEFINED_SPLITS_LVIS.items():
+        for key, (image_root, json_file) in splits_per_dataset.items():
+            register_lvis_instances(
+                key,
+                get_lvis_instances_meta(dataset_name),
+                os.path.join(root, json_file) if "://" not in json_file else json_file,
+                os.path.join(root, image_root),
+            )
+
+
+# ==== Predefined splits for raw cityscapes images ===========
+_RAW_CITYSCAPES_SPLITS = {
+    "cityscapes_fine_{task}_train": ("cityscapes/leftImg8bit/train/", "cityscapes/gtFine/train/"),
+    "cityscapes_fine_{task}_val": ("cityscapes/leftImg8bit/val/", "cityscapes/gtFine/val/"),
+    "cityscapes_fine_{task}_test": ("cityscapes/leftImg8bit/test/", "cityscapes/gtFine/test/"),
+}
+
+
+def register_all_cityscapes(root):
+    for key, (image_dir, gt_dir) in _RAW_CITYSCAPES_SPLITS.items():
+        meta = _get_builtin_metadata("cityscapes")
+        image_dir = os.path.join(root, image_dir)
+        gt_dir = os.path.join(root, gt_dir)
+
+        inst_key = key.format(task="instance_seg")
+        DatasetCatalog.register(
+            inst_key,
+            lambda x=image_dir, y=gt_dir: load_cityscapes_instances(
+                x, y, from_json=True, to_polygons=True
+            ),
+        )
+        MetadataCatalog.get(inst_key).set(
+            image_dir=image_dir, gt_dir=gt_dir, evaluator_type="cityscapes_instance", **meta
+        )
+
+        sem_key = key.format(task="sem_seg")
+        DatasetCatalog.register(
+            sem_key, lambda x=image_dir, y=gt_dir: load_cityscapes_semantic(x, y)
+        )
+        MetadataCatalog.get(sem_key).set(
+            image_dir=image_dir,
+            gt_dir=gt_dir,
+            evaluator_type="cityscapes_sem_seg",
+            ignore_label=255,
+            **meta,
+        )
+
+
+# ==== Predefined splits for PASCAL VOC ===========
+def register_all_pascal_voc(root):
+    SPLITS = [
+        ("voc_2007_trainval", "VOC2007", "trainval"),
+        ("voc_2007_train", "VOC2007", "train"),
+        ("voc_2007_val", "VOC2007", "val"),
+        ("voc_2007_test", "VOC2007", "test"),
+        ("voc_2012_trainval", "VOC2012", "trainval"),
+        ("voc_2012_train", "VOC2012", "train"),
+        ("voc_2012_val", "VOC2012", "val"),
+    ]
+    for name, dirname, split in SPLITS:
+        year = 2007 if "2007" in name else 2012
+        register_pascal_voc(name, os.path.join(root, dirname), split, year)
+        MetadataCatalog.get(name).evaluator_type = "pascal_voc"
+
+
+def register_all_ade20k(root):
+    root = os.path.join(root, "ADEChallengeData2016")
+    for name, dirname in [("train", "training"), ("val", "validation")]:
+        image_dir = os.path.join(root, "images", dirname)
+        gt_dir = os.path.join(root, "annotations_detectron2", dirname)
+        name = f"ade20k_sem_seg_{name}"
+        DatasetCatalog.register(
+            name, lambda x=image_dir, y=gt_dir: load_sem_seg(y, x, gt_ext="png", image_ext="jpg")
+        )
+        MetadataCatalog.get(name).set(
+            stuff_classes=ADE20K_SEM_SEG_CATEGORIES[:],
+            image_root=image_dir,
+            sem_seg_root=gt_dir,
+            evaluator_type="sem_seg",
+            ignore_label=255,
+        )
+
+
+# True for open source;
+# Internally at fb, we register them elsewhere
+if __name__.endswith(".builtin"):
+    # Assume pre-defined datasets live in `./datasets`.
+    _root = os.path.expanduser(os.getenv("DETECTRON2_DATASETS", "datasets"))
+    register_all_coco(_root)
+    register_all_lvis(_root)
+    register_all_cityscapes(_root)
+    register_all_cityscapes_panoptic(_root)
+    register_all_pascal_voc(_root)
+    register_all_ade20k(_root)

detectron2/data/datasets/builtin_meta.py

@@ -0,0 +1,350 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+"""
+Note:
+For your custom dataset, there is no need to hard-code metadata anywhere in the code.
+For example, for COCO-format dataset, metadata will be obtained automatically
+when calling `load_coco_json`. For other dataset, metadata may also be obtained in other ways
+during loading.
+
+However, we hard-coded metadata for a few common dataset here.
+The only goal is to allow users who don't have these dataset to use pre-trained models.
+Users don't have to download a COCO json (which contains metadata), in order to visualize a
+COCO model (with correct class names and colors).
+"""
+
+
+# All coco categories, together with their nice-looking visualization colors
+# It's from https://github.com/cocodataset/panopticapi/blob/master/panoptic_coco_categories.json
+COCO_CATEGORIES = [
+    {"color": [220, 20, 60], "isthing": 1, "id": 1, "name": "person"},
+    {"color": [119, 11, 32], "isthing": 1, "id": 2, "name": "bicycle"},
+    {"color": [0, 0, 142], "isthing": 1, "id": 3, "name": "car"},
+    {"color": [0, 0, 230], "isthing": 1, "id": 4, "name": "motorcycle"},
+    {"color": [106, 0, 228], "isthing": 1, "id": 5, "name": "airplane"},
+    {"color": [0, 60, 100], "isthing": 1, "id": 6, "name": "bus"},
+    {"color": [0, 80, 100], "isthing": 1, "id": 7, "name": "train"},
+    {"color": [0, 0, 70], "isthing": 1, "id": 8, "name": "truck"},
+    {"color": [0, 0, 192], "isthing": 1, "id": 9, "name": "boat"},
+    {"color": [250, 170, 30], "isthing": 1, "id": 10, "name": "traffic light"},
+    {"color": [100, 170, 30], "isthing": 1, "id": 11, "name": "fire hydrant"},
+    {"color": [220, 220, 0], "isthing": 1, "id": 13, "name": "stop sign"},
+    {"color": [175, 116, 175], "isthing": 1, "id": 14, "name": "parking meter"},
+    {"color": [250, 0, 30], "isthing": 1, "id": 15, "name": "bench"},
+    {"color": [165, 42, 42], "isthing": 1, "id": 16, "name": "bird"},
+    {"color": [255, 77, 255], "isthing": 1, "id": 17, "name": "cat"},
+    {"color": [0, 226, 252], "isthing": 1, "id": 18, "name": "dog"},
+    {"color": [182, 182, 255], "isthing": 1, "id": 19, "name": "horse"},
+    {"color": [0, 82, 0], "isthing": 1, "id": 20, "name": "sheep"},
+    {"color": [120, 166, 157], "isthing": 1, "id": 21, "name": "cow"},
+    {"color": [110, 76, 0], "isthing": 1, "id": 22, "name": "elephant"},
+    {"color": [174, 57, 255], "isthing": 1, "id": 23, "name": "bear"},
+    {"color": [199, 100, 0], "isthing": 1, "id": 24, "name": "zebra"},
+    {"color": [72, 0, 118], "isthing": 1, "id": 25, "name": "giraffe"},
+    {"color": [255, 179, 240], "isthing": 1, "id": 27, "name": "backpack"},
+    {"color": [0, 125, 92], "isthing": 1, "id": 28, "name": "umbrella"},
+    {"color": [209, 0, 151], "isthing": 1, "id": 31, "name": "handbag"},
+    {"color": [188, 208, 182], "isthing": 1, "id": 32, "name": "tie"},
+    {"color": [0, 220, 176], "isthing": 1, "id": 33, "name": "suitcase"},
+    {"color": [255, 99, 164], "isthing": 1, "id": 34, "name": "frisbee"},
+    {"color": [92, 0, 73], "isthing": 1, "id": 35, "name": "skis"},
+    {"color": [133, 129, 255], "isthing": 1, "id": 36, "name": "snowboard"},
+    {"color": [78, 180, 255], "isthing": 1, "id": 37, "name": "sports ball"},
+    {"color": [0, 228, 0], "isthing": 1, "id": 38, "name": "kite"},
+    {"color": [174, 255, 243], "isthing": 1, "id": 39, "name": "baseball bat"},
+    {"color": [45, 89, 255], "isthing": 1, "id": 40, "name": "baseball glove"},
+    {"color": [134, 134, 103], "isthing": 1, "id": 41, "name": "skateboard"},
+    {"color": [145, 148, 174], "isthing": 1, "id": 42, "name": "surfboard"},
+    {"color": [255, 208, 186], "isthing": 1, "id": 43, "name": "tennis racket"},
+    {"color": [197, 226, 255], "isthing": 1, "id": 44, "name": "bottle"},
+    {"color": [171, 134, 1], "isthing": 1, "id": 46, "name": "wine glass"},
+    {"color": [109, 63, 54], "isthing": 1, "id": 47, "name": "cup"},
+    {"color": [207, 138, 255], "isthing": 1, "id": 48, "name": "fork"},
+    {"color": [151, 0, 95], "isthing": 1, "id": 49, "name": "knife"},
+    {"color": [9, 80, 61], "isthing": 1, "id": 50, "name": "spoon"},
+    {"color": [84, 105, 51], "isthing": 1, "id": 51, "name": "bowl"},
+    {"color": [74, 65, 105], "isthing": 1, "id": 52, "name": "banana"},
+    {"color": [166, 196, 102], "isthing": 1, "id": 53, "name": "apple"},
+    {"color": [208, 195, 210], "isthing": 1, "id": 54, "name": "sandwich"},
+    {"color": [255, 109, 65], "isthing": 1, "id": 55, "name": "orange"},
+    {"color": [0, 143, 149], "isthing": 1, "id": 56, "name": "broccoli"},
+    {"color": [179, 0, 194], "isthing": 1, "id": 57, "name": "carrot"},
+    {"color": [209, 99, 106], "isthing": 1, "id": 58, "name": "hot dog"},
+    {"color": [5, 121, 0], "isthing": 1, "id": 59, "name": "pizza"},
+    {"color": [227, 255, 205], "isthing": 1, "id": 60, "name": "donut"},
+    {"color": [147, 186, 208], "isthing": 1, "id": 61, "name": "cake"},
+    {"color": [153, 69, 1], "isthing": 1, "id": 62, "name": "chair"},
+    {"color": [3, 95, 161], "isthing": 1, "id": 63, "name": "couch"},
+    {"color": [163, 255, 0], "isthing": 1, "id": 64, "name": "potted plant"},
+    {"color": [119, 0, 170], "isthing": 1, "id": 65, "name": "bed"},
+    {"color": [0, 182, 199], "isthing": 1, "id": 67, "name": "dining table"},
+    {"color": [0, 165, 120], "isthing": 1, "id": 70, "name": "toilet"},
+    {"color": [183, 130, 88], "isthing": 1, "id": 72, "name": "tv"},
+    {"color": [95, 32, 0], "isthing": 1, "id": 73, "name": "laptop"},
+    {"color": [130, 114, 135], "isthing": 1, "id": 74, "name": "mouse"},
+    {"color": [110, 129, 133], "isthing": 1, "id": 75, "name": "remote"},
+    {"color": [166, 74, 118], "isthing": 1, "id": 76, "name": "keyboard"},
+    {"color": [219, 142, 185], "isthing": 1, "id": 77, "name": "cell phone"},
+    {"color": [79, 210, 114], "isthing": 1, "id": 78, "name": "microwave"},
+    {"color": [178, 90, 62], "isthing": 1, "id": 79, "name": "oven"},
+    {"color": [65, 70, 15], "isthing": 1, "id": 80, "name": "toaster"},
+    {"color": [127, 167, 115], "isthing": 1, "id": 81, "name": "sink"},
+    {"color": [59, 105, 106], "isthing": 1, "id": 82, "name": "refrigerator"},
+    {"color": [142, 108, 45], "isthing": 1, "id": 84, "name": "book"},
+    {"color": [196, 172, 0], "isthing": 1, "id": 85, "name": "clock"},
+    {"color": [95, 54, 80], "isthing": 1, "id": 86, "name": "vase"},
+    {"color": [128, 76, 255], "isthing": 1, "id": 87, "name": "scissors"},
+    {"color": [201, 57, 1], "isthing": 1, "id": 88, "name": "teddy bear"},
+    {"color": [246, 0, 122], "isthing": 1, "id": 89, "name": "hair drier"},
+    {"color": [191, 162, 208], "isthing": 1, "id": 90, "name": "toothbrush"},
+    {"color": [255, 255, 128], "isthing": 0, "id": 92, "name": "banner"},
+    {"color": [147, 211, 203], "isthing": 0, "id": 93, "name": "blanket"},
+    {"color": [150, 100, 100], "isthing": 0, "id": 95, "name": "bridge"},
+    {"color": [168, 171, 172], "isthing": 0, "id": 100, "name": "cardboard"},
+    {"color": [146, 112, 198], "isthing": 0, "id": 107, "name": "counter"},
+    {"color": [210, 170, 100], "isthing": 0, "id": 109, "name": "curtain"},
+    {"color": [92, 136, 89], "isthing": 0, "id": 112, "name": "door-stuff"},
+    {"color": [218, 88, 184], "isthing": 0, "id": 118, "name": "floor-wood"},
+    {"color": [241, 129, 0], "isthing": 0, "id": 119, "name": "flower"},
+    {"color": [217, 17, 255], "isthing": 0, "id": 122, "name": "fruit"},
+    {"color": [124, 74, 181], "isthing": 0, "id": 125, "name": "gravel"},
+    {"color": [70, 70, 70], "isthing": 0, "id": 128, "name": "house"},
+    {"color": [255, 228, 255], "isthing": 0, "id": 130, "name": "light"},
+    {"color": [154, 208, 0], "isthing": 0, "id": 133, "name": "mirror-stuff"},
+    {"color": [193, 0, 92], "isthing": 0, "id": 138, "name": "net"},
+    {"color": [76, 91, 113], "isthing": 0, "id": 141, "name": "pillow"},
+    {"color": [255, 180, 195], "isthing": 0, "id": 144, "name": "platform"},
+    {"color": [106, 154, 176], "isthing": 0, "id": 145, "name": "playingfield"},
+    {"color": [230, 150, 140], "isthing": 0, "id": 147, "name": "railroad"},
+    {"color": [60, 143, 255], "isthing": 0, "id": 148, "name": "river"},
+    {"color": [128, 64, 128], "isthing": 0, "id": 149, "name": "road"},
+    {"color": [92, 82, 55], "isthing": 0, "id": 151, "name": "roof"},
+    {"color": [254, 212, 124], "isthing": 0, "id": 154, "name": "sand"},
+    {"color": [73, 77, 174], "isthing": 0, "id": 155, "name": "sea"},
+    {"color": [255, 160, 98], "isthing": 0, "id": 156, "name": "shelf"},
+    {"color": [255, 255, 255], "isthing": 0, "id": 159, "name": "snow"},
+    {"color": [104, 84, 109], "isthing": 0, "id": 161, "name": "stairs"},
+    {"color": [169, 164, 131], "isthing": 0, "id": 166, "name": "tent"},
+    {"color": [225, 199, 255], "isthing": 0, "id": 168, "name": "towel"},
+    {"color": [137, 54, 74], "isthing": 0, "id": 171, "name": "wall-brick"},
+    {"color": [135, 158, 223], "isthing": 0, "id": 175, "name": "wall-stone"},
+    {"color": [7, 246, 231], "isthing": 0, "id": 176, "name": "wall-tile"},
+    {"color": [107, 255, 200], "isthing": 0, "id": 177, "name": "wall-wood"},
+    {"color": [58, 41, 149], "isthing": 0, "id": 178, "name": "water-other"},
+    {"color": [183, 121, 142], "isthing": 0, "id": 180, "name": "window-blind"},
+    {"color": [255, 73, 97], "isthing": 0, "id": 181, "name": "window-other"},
+    {"color": [107, 142, 35], "isthing": 0, "id": 184, "name": "tree-merged"},
+    {"color": [190, 153, 153], "isthing": 0, "id": 185, "name": "fence-merged"},
+    {"color": [146, 139, 141], "isthing": 0, "id": 186, "name": "ceiling-merged"},
+    {"color": [70, 130, 180], "isthing": 0, "id": 187, "name": "sky-other-merged"},
+    {"color": [134, 199, 156], "isthing": 0, "id": 188, "name": "cabinet-merged"},
+    {"color": [209, 226, 140], "isthing": 0, "id": 189, "name": "table-merged"},
+    {"color": [96, 36, 108], "isthing": 0, "id": 190, "name": "floor-other-merged"},
+    {"color": [96, 96, 96], "isthing": 0, "id": 191, "name": "pavement-merged"},
+    {"color": [64, 170, 64], "isthing": 0, "id": 192, "name": "mountain-merged"},
+    {"color": [152, 251, 152], "isthing": 0, "id": 193, "name": "grass-merged"},
+    {"color": [208, 229, 228], "isthing": 0, "id": 194, "name": "dirt-merged"},
+    {"color": [206, 186, 171], "isthing": 0, "id": 195, "name": "paper-merged"},
+    {"color": [152, 161, 64], "isthing": 0, "id": 196, "name": "food-other-merged"},
+    {"color": [116, 112, 0], "isthing": 0, "id": 197, "name": "building-other-merged"},
+    {"color": [0, 114, 143], "isthing": 0, "id": 198, "name": "rock-merged"},
+    {"color": [102, 102, 156], "isthing": 0, "id": 199, "name": "wall-other-merged"},
+    {"color": [250, 141, 255], "isthing": 0, "id": 200, "name": "rug-merged"},
+]
+
+# fmt: off
+COCO_PERSON_KEYPOINT_NAMES = (
+    "nose",
+    "left_eye", "right_eye",
+    "left_ear", "right_ear",
+    "left_shoulder", "right_shoulder",
+    "left_elbow", "right_elbow",
+    "left_wrist", "right_wrist",
+    "left_hip", "right_hip",
+    "left_knee", "right_knee",
+    "left_ankle", "right_ankle",
+)
+# fmt: on
+
+# Pairs of keypoints that should be exchanged under horizontal flipping
+COCO_PERSON_KEYPOINT_FLIP_MAP = (
+    ("left_eye", "right_eye"),
+    ("left_ear", "right_ear"),
+    ("left_shoulder", "right_shoulder"),
+    ("left_elbow", "right_elbow"),
+    ("left_wrist", "right_wrist"),
+    ("left_hip", "right_hip"),
+    ("left_knee", "right_knee"),
+    ("left_ankle", "right_ankle"),
+)
+
+# rules for pairs of keypoints to draw a line between, and the line color to use.
+KEYPOINT_CONNECTION_RULES = [
+    # face
+    ("left_ear", "left_eye", (102, 204, 255)),
+    ("right_ear", "right_eye", (51, 153, 255)),
+    ("left_eye", "nose", (102, 0, 204)),
+    ("nose", "right_eye", (51, 102, 255)),
+    # upper-body
+    ("left_shoulder", "right_shoulder", (255, 128, 0)),
+    ("left_shoulder", "left_elbow", (153, 255, 204)),
+    ("right_shoulder", "right_elbow", (128, 229, 255)),
+    ("left_elbow", "left_wrist", (153, 255, 153)),
+    ("right_elbow", "right_wrist", (102, 255, 224)),
+    # lower-body
+    ("left_hip", "right_hip", (255, 102, 0)),
+    ("left_hip", "left_knee", (255, 255, 77)),
+    ("right_hip", "right_knee", (153, 255, 204)),
+    ("left_knee", "left_ankle", (191, 255, 128)),
+    ("right_knee", "right_ankle", (255, 195, 77)),
+]
+
+# All Cityscapes categories, together with their nice-looking visualization colors
+# It's from https://github.com/mcordts/cityscapesScripts/blob/master/cityscapesscripts/helpers/labels.py  # noqa
+CITYSCAPES_CATEGORIES = [
+    {"color": (128, 64, 128), "isthing": 0, "id": 7, "trainId": 0, "name": "road"},
+    {"color": (244, 35, 232), "isthing": 0, "id": 8, "trainId": 1, "name": "sidewalk"},
+    {"color": (70, 70, 70), "isthing": 0, "id": 11, "trainId": 2, "name": "building"},
+    {"color": (102, 102, 156), "isthing": 0, "id": 12, "trainId": 3, "name": "wall"},
+    {"color": (190, 153, 153), "isthing": 0, "id": 13, "trainId": 4, "name": "fence"},
+    {"color": (153, 153, 153), "isthing": 0, "id": 17, "trainId": 5, "name": "pole"},
+    {"color": (250, 170, 30), "isthing": 0, "id": 19, "trainId": 6, "name": "traffic light"},
+    {"color": (220, 220, 0), "isthing": 0, "id": 20, "trainId": 7, "name": "traffic sign"},
+    {"color": (107, 142, 35), "isthing": 0, "id": 21, "trainId": 8, "name": "vegetation"},
+    {"color": (152, 251, 152), "isthing": 0, "id": 22, "trainId": 9, "name": "terrain"},
+    {"color": (70, 130, 180), "isthing": 0, "id": 23, "trainId": 10, "name": "sky"},
+    {"color": (220, 20, 60), "isthing": 1, "id": 24, "trainId": 11, "name": "person"},
+    {"color": (255, 0, 0), "isthing": 1, "id": 25, "trainId": 12, "name": "rider"},
+    {"color": (0, 0, 142), "isthing": 1, "id": 26, "trainId": 13, "name": "car"},
+    {"color": (0, 0, 70), "isthing": 1, "id": 27, "trainId": 14, "name": "truck"},
+    {"color": (0, 60, 100), "isthing": 1, "id": 28, "trainId": 15, "name": "bus"},
+    {"color": (0, 80, 100), "isthing": 1, "id": 31, "trainId": 16, "name": "train"},
+    {"color": (0, 0, 230), "isthing": 1, "id": 32, "trainId": 17, "name": "motorcycle"},
+    {"color": (119, 11, 32), "isthing": 1, "id": 33, "trainId": 18, "name": "bicycle"},
+]
+
+# fmt: off
+ADE20K_SEM_SEG_CATEGORIES = [
+    "wall", "building", "sky", "floor", "tree", "ceiling", "road, route", "bed", "window ", "grass", "cabinet", "sidewalk, pavement", "person", "earth, ground", "door", "table", "mountain, mount", "plant", "curtain", "chair", "car", "water", "painting, picture", "sofa", "shelf", "house", "sea", "mirror", "rug", "field", "armchair", "seat", "fence", "desk", "rock, stone", "wardrobe, closet, press", "lamp", "tub", "rail", "cushion", "base, pedestal, stand", "box", "column, pillar", "signboard, sign", "chest of drawers, chest, bureau, dresser", "counter", "sand", "sink", "skyscraper", "fireplace", "refrigerator, icebox", "grandstand, covered stand", "path", "stairs", "runway", "case, display case, showcase, vitrine", "pool table, billiard table, snooker table", "pillow", "screen door, screen", "stairway, staircase", "river", "bridge, span", "bookcase", "blind, screen", "coffee table", "toilet, can, commode, crapper, pot, potty, stool, throne", "flower", "book", "hill", "bench", "countertop", "stove", "palm, palm tree", "kitchen island", "computer", "swivel chair", "boat", "bar", "arcade machine", "hovel, hut, hutch, shack, shanty", "bus", "towel", "light", "truck", "tower", "chandelier", "awning, sunshade, sunblind", "street lamp", "booth", "tv", "plane", "dirt track", "clothes", "pole", "land, ground, soil", "bannister, banister, balustrade, balusters, handrail", "escalator, moving staircase, moving stairway", "ottoman, pouf, pouffe, puff, hassock", "bottle", "buffet, counter, sideboard", "poster, posting, placard, notice, bill, card", "stage", "van", "ship", "fountain", "conveyer belt, conveyor belt, conveyer, conveyor, transporter", "canopy", "washer, automatic washer, washing machine", "plaything, toy", "pool", "stool", "barrel, cask", "basket, handbasket", "falls", "tent", "bag", "minibike, motorbike", "cradle", "oven", "ball", "food, solid food", "step, stair", "tank, storage tank", "trade name", "microwave", "pot", "animal", "bicycle", "lake", "dishwasher", "screen", "blanket, cover", "sculpture", "hood, exhaust hood", "sconce", "vase", "traffic light", "tray", "trash can", "fan", "pier", "crt screen", "plate", "monitor", "bulletin board", "shower", "radiator", "glass, drinking glass", "clock", "flag", # noqa
+]
+# After processed by `prepare_ade20k_sem_seg.py`, id 255 means ignore
+# fmt: on
+
+
+def _get_coco_instances_meta():
+    thing_ids = [k["id"] for k in COCO_CATEGORIES if k["isthing"] == 1]
+    thing_colors = [k["color"] for k in COCO_CATEGORIES if k["isthing"] == 1]
+    assert len(thing_ids) == 80, len(thing_ids)
+    # Mapping from the incontiguous COCO category id to an id in [0, 79]
+    thing_dataset_id_to_contiguous_id = {k: i for i, k in enumerate(thing_ids)}
+    thing_classes = [k["name"] for k in COCO_CATEGORIES if k["isthing"] == 1]
+    ret = {
+        "thing_dataset_id_to_contiguous_id": thing_dataset_id_to_contiguous_id,
+        "thing_classes": thing_classes,
+        "thing_colors": thing_colors,
+    }
+    return ret
+
+
+def _get_coco_panoptic_separated_meta():
+    """
+    Returns metadata for "separated" version of the panoptic segmentation dataset.
+    """
+    stuff_ids = [k["id"] for k in COCO_CATEGORIES if k["isthing"] == 0]
+    assert len(stuff_ids) == 53, len(stuff_ids)
+
+    # For semantic segmentation, this mapping maps from contiguous stuff id
+    # (in [0, 53], used in models) to ids in the dataset (used for processing results)
+    # The id 0 is mapped to an extra category "thing".
+    stuff_dataset_id_to_contiguous_id = {k: i + 1 for i, k in enumerate(stuff_ids)}
+    # When converting COCO panoptic annotations to semantic annotations
+    # We label the "thing" category to 0
+    stuff_dataset_id_to_contiguous_id[0] = 0
+
+    # 54 names for COCO stuff categories (including "things")
+    stuff_classes = ["things"] + [
+        k["name"].replace("-other", "").replace("-merged", "")
+        for k in COCO_CATEGORIES
+        if k["isthing"] == 0
+    ]
+
+    # NOTE: I randomly picked a color for things
+    stuff_colors = [[82, 18, 128]] + [k["color"] for k in COCO_CATEGORIES if k["isthing"] == 0]
+    ret = {
+        "stuff_dataset_id_to_contiguous_id": stuff_dataset_id_to_contiguous_id,
+        "stuff_classes": stuff_classes,
+        "stuff_colors": stuff_colors,
+    }
+    ret.update(_get_coco_instances_meta())
+    return ret
+
+
+def _get_builtin_metadata(dataset_name):
+    if dataset_name == "coco":
+        return _get_coco_instances_meta()
+    if dataset_name == "coco_panoptic_separated":
+        return _get_coco_panoptic_separated_meta()
+    elif dataset_name == "coco_panoptic_standard":
+        meta = {}
+        # The following metadata maps contiguous id from [0, #thing categories +
+        # #stuff categories) to their names and colors. We have to replica of the
+        # same name and color under "thing_*" and "stuff_*" because the current
+        # visualization function in D2 handles thing and class classes differently
+        # due to some heuristic used in Panoptic FPN. We keep the same naming to
+        # enable reusing existing visualization functions.
+        thing_classes = [k["name"] for k in COCO_CATEGORIES]
+        thing_colors = [k["color"] for k in COCO_CATEGORIES]
+        stuff_classes = [k["name"] for k in COCO_CATEGORIES]
+        stuff_colors = [k["color"] for k in COCO_CATEGORIES]
+
+        meta["thing_classes"] = thing_classes
+        meta["thing_colors"] = thing_colors
+        meta["stuff_classes"] = stuff_classes
+        meta["stuff_colors"] = stuff_colors
+
+        # Convert category id for training:
+        #   category id: like semantic segmentation, it is the class id for each
+        #   pixel. Since there are some classes not used in evaluation, the category
+        #   id is not always contiguous and thus we have two set of category ids:
+        #       - original category id: category id in the original dataset, mainly
+        #           used for evaluation.
+        #       - contiguous category id: [0, #classes), in order to train the linear
+        #           softmax classifier.
+        thing_dataset_id_to_contiguous_id = {}
+        stuff_dataset_id_to_contiguous_id = {}
+
+        for i, cat in enumerate(COCO_CATEGORIES):
+            if cat["isthing"]:
+                thing_dataset_id_to_contiguous_id[cat["id"]] = i
+            else:
+                stuff_dataset_id_to_contiguous_id[cat["id"]] = i
+
+        meta["thing_dataset_id_to_contiguous_id"] = thing_dataset_id_to_contiguous_id
+        meta["stuff_dataset_id_to_contiguous_id"] = stuff_dataset_id_to_contiguous_id
+
+        return meta
+    elif dataset_name == "coco_person":
+        return {
+            "thing_classes": ["person"],
+            "keypoint_names": COCO_PERSON_KEYPOINT_NAMES,
+            "keypoint_flip_map": COCO_PERSON_KEYPOINT_FLIP_MAP,
+            "keypoint_connection_rules": KEYPOINT_CONNECTION_RULES,
+        }
+    elif dataset_name == "cityscapes":
+        # fmt: off
+        CITYSCAPES_THING_CLASSES = [
+            "person", "rider", "car", "truck",
+            "bus", "train", "motorcycle", "bicycle",
+        ]
+        CITYSCAPES_STUFF_CLASSES = [
+            "road", "sidewalk", "building", "wall", "fence", "pole", "traffic light",
+            "traffic sign", "vegetation", "terrain", "sky", "person", "rider", "car",
+            "truck", "bus", "train", "motorcycle", "bicycle",
+        ]
+        # fmt: on
+        return {
+            "thing_classes": CITYSCAPES_THING_CLASSES,
+            "stuff_classes": CITYSCAPES_STUFF_CLASSES,
+        }
+    raise KeyError("No built-in metadata for dataset {}".format(dataset_name))

detectron2/data/datasets/cityscapes.py

@@ -0,0 +1,334 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import functools
+import json
+import logging
+import multiprocessing as mp
+import numpy as np
+import os
+from itertools import chain
+import pycocotools.mask as mask_util
+from PIL import Image
+
+from detectron2.structures import BoxMode
+from detectron2.utils.comm import get_world_size
+from detectron2.utils.file_io import PathManager
+from detectron2.utils.logger import setup_logger
+
+try:
+    import cv2  # noqa
+except ImportError:
+    # OpenCV is an optional dependency at the moment
+    pass
+
+
+logger = logging.getLogger(__name__)
+
+
+def _get_cityscapes_files(image_dir, gt_dir):
+    files = []
+    # scan through the directory
+    cities = PathManager.ls(image_dir)
+    logger.info(f"{len(cities)} cities found in '{image_dir}'.")
+    for city in cities:
+        city_img_dir = os.path.join(image_dir, city)
+        city_gt_dir = os.path.join(gt_dir, city)
+        for basename in PathManager.ls(city_img_dir):
+            image_file = os.path.join(city_img_dir, basename)
+
+            suffix = "leftImg8bit.png"
+            assert basename.endswith(suffix), basename
+            basename = basename[: -len(suffix)]
+
+            instance_file = os.path.join(city_gt_dir, basename + "gtFine_instanceIds.png")
+            label_file = os.path.join(city_gt_dir, basename + "gtFine_labelIds.png")
+            json_file = os.path.join(city_gt_dir, basename + "gtFine_polygons.json")
+
+            files.append((image_file, instance_file, label_file, json_file))
+    assert len(files), "No images found in {}".format(image_dir)
+    for f in files[0]:
+        assert PathManager.isfile(f), f
+    return files
+
+
+def load_cityscapes_instances(image_dir, gt_dir, from_json=True, to_polygons=True):
+    """
+    Args:
+        image_dir (str): path to the raw dataset. e.g., "~/cityscapes/leftImg8bit/train".
+        gt_dir (str): path to the raw annotations. e.g., "~/cityscapes/gtFine/train".
+        from_json (bool): whether to read annotations from the raw json file or the png files.
+        to_polygons (bool): whether to represent the segmentation as polygons
+            (COCO's format) instead of masks (cityscapes's format).
+
+    Returns:
+        list[dict]: a list of dicts in Detectron2 standard format. (See
+        `Using Custom Datasets </tutorials/datasets.html>`_ )
+    """
+    if from_json:
+        assert to_polygons, (
+            "Cityscapes's json annotations are in polygon format. "
+            "Converting to mask format is not supported now."
+        )
+    files = _get_cityscapes_files(image_dir, gt_dir)
+
+    logger.info("Preprocessing cityscapes annotations ...")
+    # This is still not fast: all workers will execute duplicate works and will
+    # take up to 10m on a 8GPU server.
+    pool = mp.Pool(processes=max(mp.cpu_count() // get_world_size() // 2, 4))
+
+    ret = pool.map(
+        functools.partial(_cityscapes_files_to_dict, from_json=from_json, to_polygons=to_polygons),
+        files,
+    )
+    logger.info("Loaded {} images from {}".format(len(ret), image_dir))
+
+    # Map cityscape ids to contiguous ids
+    from cityscapesscripts.helpers.labels import labels
+
+    labels = [l for l in labels if l.hasInstances and not l.ignoreInEval]
+    dataset_id_to_contiguous_id = {l.id: idx for idx, l in enumerate(labels)}
+    for dict_per_image in ret:
+        for anno in dict_per_image["annotations"]:
+            anno["category_id"] = dataset_id_to_contiguous_id[anno["category_id"]]
+    return ret
+
+
+def load_cityscapes_semantic(image_dir, gt_dir):
+    """
+    Args:
+        image_dir (str): path to the raw dataset. e.g., "~/cityscapes/leftImg8bit/train".
+        gt_dir (str): path to the raw annotations. e.g., "~/cityscapes/gtFine/train".
+
+    Returns:
+        list[dict]: a list of dict, each has "file_name" and
+            "sem_seg_file_name".
+    """
+    ret = []
+    # gt_dir is small and contain many small files. make sense to fetch to local first
+    gt_dir = PathManager.get_local_path(gt_dir)
+    for image_file, _, label_file, json_file in _get_cityscapes_files(image_dir, gt_dir):
+        label_file = label_file.replace("labelIds", "labelTrainIds")
+
+        with PathManager.open(json_file, "r") as f:
+            jsonobj = json.load(f)
+        ret.append(
+            {
+                "file_name": image_file,
+                "sem_seg_file_name": label_file,
+                "height": jsonobj["imgHeight"],
+                "width": jsonobj["imgWidth"],
+            }
+        )
+    assert len(ret), f"No images found in {image_dir}!"
+    assert PathManager.isfile(
+        ret[0]["sem_seg_file_name"]
+    ), "Please generate labelTrainIds.png with cityscapesscripts/preparation/createTrainIdLabelImgs.py"  # noqa
+    return ret
+
+
+def _cityscapes_files_to_dict(files, from_json, to_polygons):
+    """
+    Parse cityscapes annotation files to a instance segmentation dataset dict.
+
+    Args:
+        files (tuple): consists of (image_file, instance_id_file, label_id_file, json_file)
+        from_json (bool): whether to read annotations from the raw json file or the png files.
+        to_polygons (bool): whether to represent the segmentation as polygons
+            (COCO's format) instead of masks (cityscapes's format).
+
+    Returns:
+        A dict in Detectron2 Dataset format.
+    """
+    from cityscapesscripts.helpers.labels import id2label, name2label
+
+    image_file, instance_id_file, _, json_file = files
+
+    annos = []
+
+    if from_json:
+        from shapely.geometry import MultiPolygon, Polygon
+
+        with PathManager.open(json_file, "r") as f:
+            jsonobj = json.load(f)
+        ret = {
+            "file_name": image_file,
+            "image_id": os.path.basename(image_file),
+            "height": jsonobj["imgHeight"],
+            "width": jsonobj["imgWidth"],
+        }
+
+        # `polygons_union` contains the union of all valid polygons.
+        polygons_union = Polygon()
+
+        # CityscapesScripts draw the polygons in sequential order
+        # and each polygon *overwrites* existing ones. See
+        # (https://github.com/mcordts/cityscapesScripts/blob/master/cityscapesscripts/preparation/json2instanceImg.py) # noqa
+        # We use reverse order, and each polygon *avoids* early ones.
+        # This will resolve the ploygon overlaps in the same way as CityscapesScripts.
+        for obj in jsonobj["objects"][::-1]:
+            if "deleted" in obj:  # cityscapes data format specific
+                continue
+            label_name = obj["label"]
+
+            try:
+                label = name2label[label_name]
+            except KeyError:
+                if label_name.endswith("group"):  # crowd area
+                    label = name2label[label_name[: -len("group")]]
+                else:
+                    raise
+            if label.id < 0:  # cityscapes data format
+                continue
+
+            # Cityscapes's raw annotations uses integer coordinates
+            # Therefore +0.5 here
+            poly_coord = np.asarray(obj["polygon"], dtype="f4") + 0.5
+            # CityscapesScript uses PIL.ImageDraw.polygon to rasterize
+            # polygons for evaluation. This function operates in integer space
+            # and draws each pixel whose center falls into the polygon.
+            # Therefore it draws a polygon which is 0.5 "fatter" in expectation.
+            # We therefore dilate the input polygon by 0.5 as our input.
+            poly = Polygon(poly_coord).buffer(0.5, resolution=4)
+
+            if not label.hasInstances or label.ignoreInEval:
+                # even if we won't store the polygon it still contributes to overlaps resolution
+                polygons_union = polygons_union.union(poly)
+                continue
+
+            # Take non-overlapping part of the polygon
+            poly_wo_overlaps = poly.difference(polygons_union)
+            if poly_wo_overlaps.is_empty:
+                continue
+            polygons_union = polygons_union.union(poly)
+
+            anno = {}
+            anno["iscrowd"] = label_name.endswith("group")
+            anno["category_id"] = label.id
+
+            if isinstance(poly_wo_overlaps, Polygon):
+                poly_list = [poly_wo_overlaps]
+            elif isinstance(poly_wo_overlaps, MultiPolygon):
+                poly_list = poly_wo_overlaps.geoms
+            else:
+                raise NotImplementedError("Unknown geometric structure {}".format(poly_wo_overlaps))
+
+            poly_coord = []
+            for poly_el in poly_list:
+                # COCO API can work only with exterior boundaries now, hence we store only them.
+                # TODO: store both exterior and interior boundaries once other parts of the
+                # codebase support holes in polygons.
+                poly_coord.append(list(chain(*poly_el.exterior.coords)))
+            anno["segmentation"] = poly_coord
+            (xmin, ymin, xmax, ymax) = poly_wo_overlaps.bounds
+
+            anno["bbox"] = (xmin, ymin, xmax, ymax)
+            anno["bbox_mode"] = BoxMode.XYXY_ABS
+
+            annos.append(anno)
+    else:
+        # See also the official annotation parsing scripts at
+        # https://github.com/mcordts/cityscapesScripts/blob/master/cityscapesscripts/evaluation/instances2dict.py  # noqa
+        with PathManager.open(instance_id_file, "rb") as f:
+            inst_image = np.asarray(Image.open(f), order="F")
+        # ids < 24 are stuff labels (filtering them first is about 5% faster)
+        flattened_ids = np.unique(inst_image[inst_image >= 24])
+
+        ret = {
+            "file_name": image_file,
+            "image_id": os.path.basename(image_file),
+            "height": inst_image.shape[0],
+            "width": inst_image.shape[1],
+        }
+
+        for instance_id in flattened_ids:
+            # For non-crowd annotations, instance_id // 1000 is the label_id
+            # Crowd annotations have <1000 instance ids
+            label_id = instance_id // 1000 if instance_id >= 1000 else instance_id
+            label = id2label[label_id]
+            if not label.hasInstances or label.ignoreInEval:
+                continue
+
+            anno = {}
+            anno["iscrowd"] = instance_id < 1000
+            anno["category_id"] = label.id
+
+            mask = np.asarray(inst_image == instance_id, dtype=np.uint8, order="F")
+
+            inds = np.nonzero(mask)
+            ymin, ymax = inds[0].min(), inds[0].max()
+            xmin, xmax = inds[1].min(), inds[1].max()
+            anno["bbox"] = (xmin, ymin, xmax, ymax)
+            if xmax <= xmin or ymax <= ymin:
+                continue
+            anno["bbox_mode"] = BoxMode.XYXY_ABS
+            if to_polygons:
+                # This conversion comes from D4809743 and D5171122,
+                # when Mask-RCNN was first developed.
+                contours = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)[
+                    -2
+                ]
+                polygons = [c.reshape(-1).tolist() for c in contours if len(c) >= 3]
+                # opencv's can produce invalid polygons
+                if len(polygons) == 0:
+                    continue
+                anno["segmentation"] = polygons
+            else:
+                anno["segmentation"] = mask_util.encode(mask[:, :, None])[0]
+            annos.append(anno)
+    ret["annotations"] = annos
+    return ret
+
+
+def main() -> None:
+    global logger, labels
+    """
+    Test the cityscapes dataset loader.
+
+    Usage:
+        python -m detectron2.data.datasets.cityscapes \
+            cityscapes/leftImg8bit/train cityscapes/gtFine/train
+    """
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument("image_dir")
+    parser.add_argument("gt_dir")
+    parser.add_argument("--type", choices=["instance", "semantic"], default="instance")
+    args = parser.parse_args()
+    from cityscapesscripts.helpers.labels import labels
+    from detectron2.data.catalog import Metadata
+    from detectron2.utils.visualizer import Visualizer
+
+    logger = setup_logger(name=__name__)
+
+    dirname = "cityscapes-data-vis"
+    os.makedirs(dirname, exist_ok=True)
+
+    if args.type == "instance":
+        dicts = load_cityscapes_instances(
+            args.image_dir, args.gt_dir, from_json=True, to_polygons=True
+        )
+        logger.info("Done loading {} samples.".format(len(dicts)))
+
+        thing_classes = [k.name for k in labels if k.hasInstances and not k.ignoreInEval]
+        meta = Metadata().set(thing_classes=thing_classes)
+
+    else:
+        dicts = load_cityscapes_semantic(args.image_dir, args.gt_dir)
+        logger.info("Done loading {} samples.".format(len(dicts)))
+
+        stuff_classes = [k.name for k in labels if k.trainId != 255]
+        stuff_colors = [k.color for k in labels if k.trainId != 255]
+        meta = Metadata().set(stuff_classes=stuff_classes, stuff_colors=stuff_colors)
+
+    for d in dicts:
+        img = np.array(Image.open(PathManager.open(d["file_name"], "rb")))
+        visualizer = Visualizer(img, metadata=meta)
+        vis = visualizer.draw_dataset_dict(d)
+        # cv2.imshow("a", vis.get_image()[:, :, ::-1])
+        # cv2.waitKey()
+        fpath = os.path.join(dirname, os.path.basename(d["file_name"]))
+        vis.save(fpath)
+
+
+if __name__ == "__main__":
+    main()  # pragma: no cover

detectron2/data/datasets/cityscapes_panoptic.py

@@ -0,0 +1,187 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import json
+import logging
+import os
+
+from detectron2.data import DatasetCatalog, MetadataCatalog
+from detectron2.data.datasets.builtin_meta import CITYSCAPES_CATEGORIES
+from detectron2.utils.file_io import PathManager
+
+"""
+This file contains functions to register the Cityscapes panoptic dataset to the DatasetCatalog.
+"""
+
+
+logger = logging.getLogger(__name__)
+
+
+def get_cityscapes_panoptic_files(image_dir, gt_dir, json_info):
+    files = []
+    # scan through the directory
+    cities = PathManager.ls(image_dir)
+    logger.info(f"{len(cities)} cities found in '{image_dir}'.")
+    image_dict = {}
+    for city in cities:
+        city_img_dir = os.path.join(image_dir, city)
+        for basename in PathManager.ls(city_img_dir):
+            image_file = os.path.join(city_img_dir, basename)
+
+            suffix = "_leftImg8bit.png"
+            assert basename.endswith(suffix), basename
+            basename = os.path.basename(basename)[: -len(suffix)]
+
+            image_dict[basename] = image_file
+
+    for ann in json_info["annotations"]:
+        image_file = image_dict.get(ann["image_id"], None)
+        assert image_file is not None, "No image {} found for annotation {}".format(
+            ann["image_id"], ann["file_name"]
+        )
+        label_file = os.path.join(gt_dir, ann["file_name"])
+        segments_info = ann["segments_info"]
+
+        files.append((image_file, label_file, segments_info))
+
+    assert len(files), "No images found in {}".format(image_dir)
+    assert PathManager.isfile(files[0][0]), files[0][0]
+    assert PathManager.isfile(files[0][1]), files[0][1]
+    return files
+
+
+def load_cityscapes_panoptic(image_dir, gt_dir, gt_json, meta):
+    """
+    Args:
+        image_dir (str): path to the raw dataset. e.g., "~/cityscapes/leftImg8bit/train".
+        gt_dir (str): path to the raw annotations. e.g.,
+            "~/cityscapes/gtFine/cityscapes_panoptic_train".
+        gt_json (str): path to the json file. e.g.,
+            "~/cityscapes/gtFine/cityscapes_panoptic_train.json".
+        meta (dict): dictionary containing "thing_dataset_id_to_contiguous_id"
+            and "stuff_dataset_id_to_contiguous_id" to map category ids to
+            contiguous ids for training.
+
+    Returns:
+        list[dict]: a list of dicts in Detectron2 standard format. (See
+        `Using Custom Datasets </tutorials/datasets.html>`_ )
+    """
+
+    def _convert_category_id(segment_info, meta):
+        if segment_info["category_id"] in meta["thing_dataset_id_to_contiguous_id"]:
+            segment_info["category_id"] = meta["thing_dataset_id_to_contiguous_id"][
+                segment_info["category_id"]
+            ]
+        else:
+            segment_info["category_id"] = meta["stuff_dataset_id_to_contiguous_id"][
+                segment_info["category_id"]
+            ]
+        return segment_info
+
+    assert os.path.exists(
+        gt_json
+    ), "Please run `python cityscapesscripts/preparation/createPanopticImgs.py` to generate label files."  # noqa
+    with open(gt_json) as f:
+        json_info = json.load(f)
+    files = get_cityscapes_panoptic_files(image_dir, gt_dir, json_info)
+    ret = []
+    for image_file, label_file, segments_info in files:
+        sem_label_file = (
+            image_file.replace("leftImg8bit", "gtFine").split(".")[0] + "_labelTrainIds.png"
+        )
+        segments_info = [_convert_category_id(x, meta) for x in segments_info]
+        ret.append(
+            {
+                "file_name": image_file,
+                "image_id": "_".join(
+                    os.path.splitext(os.path.basename(image_file))[0].split("_")[:3]
+                ),
+                "sem_seg_file_name": sem_label_file,
+                "pan_seg_file_name": label_file,
+                "segments_info": segments_info,
+            }
+        )
+    assert len(ret), f"No images found in {image_dir}!"
+    assert PathManager.isfile(
+        ret[0]["sem_seg_file_name"]
+    ), "Please generate labelTrainIds.png with cityscapesscripts/preparation/createTrainIdLabelImgs.py"  # noqa
+    assert PathManager.isfile(
+        ret[0]["pan_seg_file_name"]
+    ), "Please generate panoptic annotation with python cityscapesscripts/preparation/createPanopticImgs.py"  # noqa
+    return ret
+
+
+_RAW_CITYSCAPES_PANOPTIC_SPLITS = {
+    "cityscapes_fine_panoptic_train": (
+        "cityscapes/leftImg8bit/train",
+        "cityscapes/gtFine/cityscapes_panoptic_train",
+        "cityscapes/gtFine/cityscapes_panoptic_train.json",
+    ),
+    "cityscapes_fine_panoptic_val": (
+        "cityscapes/leftImg8bit/val",
+        "cityscapes/gtFine/cityscapes_panoptic_val",
+        "cityscapes/gtFine/cityscapes_panoptic_val.json",
+    ),
+    # "cityscapes_fine_panoptic_test": not supported yet
+}
+
+
+def register_all_cityscapes_panoptic(root):
+    meta = {}
+    # The following metadata maps contiguous id from [0, #thing categories +
+    # #stuff categories) to their names and colors. We have to replica of the
+    # same name and color under "thing_*" and "stuff_*" because the current
+    # visualization function in D2 handles thing and class classes differently
+    # due to some heuristic used in Panoptic FPN. We keep the same naming to
+    # enable reusing existing visualization functions.
+    thing_classes = [k["name"] for k in CITYSCAPES_CATEGORIES]
+    thing_colors = [k["color"] for k in CITYSCAPES_CATEGORIES]
+    stuff_classes = [k["name"] for k in CITYSCAPES_CATEGORIES]
+    stuff_colors = [k["color"] for k in CITYSCAPES_CATEGORIES]
+
+    meta["thing_classes"] = thing_classes
+    meta["thing_colors"] = thing_colors
+    meta["stuff_classes"] = stuff_classes
+    meta["stuff_colors"] = stuff_colors
+
+    # There are three types of ids in cityscapes panoptic segmentation:
+    # (1) category id: like semantic segmentation, it is the class id for each
+    #   pixel. Since there are some classes not used in evaluation, the category
+    #   id is not always contiguous and thus we have two set of category ids:
+    #       - original category id: category id in the original dataset, mainly
+    #           used for evaluation.
+    #       - contiguous category id: [0, #classes), in order to train the classifier
+    # (2) instance id: this id is used to differentiate different instances from
+    #   the same category. For "stuff" classes, the instance id is always 0; for
+    #   "thing" classes, the instance id starts from 1 and 0 is reserved for
+    #   ignored instances (e.g. crowd annotation).
+    # (3) panoptic id: this is the compact id that encode both category and
+    #   instance id by: category_id * 1000 + instance_id.
+    thing_dataset_id_to_contiguous_id = {}
+    stuff_dataset_id_to_contiguous_id = {}
+
+    for k in CITYSCAPES_CATEGORIES:
+        if k["isthing"] == 1:
+            thing_dataset_id_to_contiguous_id[k["id"]] = k["trainId"]
+        else:
+            stuff_dataset_id_to_contiguous_id[k["id"]] = k["trainId"]
+
+    meta["thing_dataset_id_to_contiguous_id"] = thing_dataset_id_to_contiguous_id
+    meta["stuff_dataset_id_to_contiguous_id"] = stuff_dataset_id_to_contiguous_id
+
+    for key, (image_dir, gt_dir, gt_json) in _RAW_CITYSCAPES_PANOPTIC_SPLITS.items():
+        image_dir = os.path.join(root, image_dir)
+        gt_dir = os.path.join(root, gt_dir)
+        gt_json = os.path.join(root, gt_json)
+
+        DatasetCatalog.register(
+            key, lambda x=image_dir, y=gt_dir, z=gt_json: load_cityscapes_panoptic(x, y, z, meta)
+        )
+        MetadataCatalog.get(key).set(
+            panoptic_root=gt_dir,
+            image_root=image_dir,
+            panoptic_json=gt_json,
+            gt_dir=gt_dir.replace("cityscapes_panoptic_", ""),
+            evaluator_type="cityscapes_panoptic_seg",
+            ignore_label=255,
+            label_divisor=1000,
+            **meta,
+        )

detectron2/data/datasets/coco.py

@@ -0,0 +1,555 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import contextlib
+import datetime
+import io
+import json
+import logging
+import numpy as np
+import os
+import shutil
+import pycocotools.mask as mask_util
+from fvcore.common.timer import Timer
+from iopath.common.file_io import file_lock
+from PIL import Image
+
+from detectron2.structures import Boxes, BoxMode, PolygonMasks, RotatedBoxes
+from detectron2.utils.file_io import PathManager
+
+from .. import DatasetCatalog, MetadataCatalog
+
+"""
+This file contains functions to parse COCO-format annotations into dicts in "Detectron2 format".
+"""
+
+
+logger = logging.getLogger(__name__)
+
+__all__ = [
+    "load_coco_json",
+    "load_sem_seg",
+    "convert_to_coco_json",
+    "register_coco_instances",
+]
+
+
+def load_coco_json(json_file, image_root, dataset_name=None, extra_annotation_keys=None):
+    """
+    Load a json file with COCO's instances annotation format.
+    Currently supports instance detection, instance segmentation,
+    and person keypoints annotations.
+
+    Args:
+        json_file (str): full path to the json file in COCO instances annotation format.
+        image_root (str or path-like): the directory where the images in this json file exists.
+        dataset_name (str or None): the name of the dataset (e.g., coco_2017_train).
+            When provided, this function will also do the following:
+
+            * Put "thing_classes" into the metadata associated with this dataset.
+            * Map the category ids into a contiguous range (needed by standard dataset format),
+              and add "thing_dataset_id_to_contiguous_id" to the metadata associated
+              with this dataset.
+
+            This option should usually be provided, unless users need to load
+            the original json content and apply more processing manually.
+        extra_annotation_keys (list[str]): list of per-annotation keys that should also be
+            loaded into the dataset dict (besides "iscrowd", "bbox", "keypoints",
+            "category_id", "segmentation"). The values for these keys will be returned as-is.
+            For example, the densepose annotations are loaded in this way.
+
+    Returns:
+        list[dict]: a list of dicts in Detectron2 standard dataset dicts format (See
+        `Using Custom Datasets </tutorials/datasets.html>`_ ) when `dataset_name` is not None.
+        If `dataset_name` is None, the returned `category_ids` may be
+        incontiguous and may not conform to the Detectron2 standard format.
+
+    Notes:
+        1. This function does not read the image files.
+           The results do not have the "image" field.
+    """
+    from pycocotools.coco import COCO
+
+    timer = Timer()
+    json_file = PathManager.get_local_path(json_file)
+    with contextlib.redirect_stdout(io.StringIO()):
+        coco_api = COCO(json_file)
+    if timer.seconds() > 1:
+        logger.info("Loading {} takes {:.2f} seconds.".format(json_file, timer.seconds()))
+
+    id_map = None
+    if dataset_name is not None:
+        meta = MetadataCatalog.get(dataset_name)
+        cat_ids = sorted(coco_api.getCatIds())
+        cats = coco_api.loadCats(cat_ids)
+        # The categories in a custom json file may not be sorted.
+        thing_classes = [c["name"] for c in sorted(cats, key=lambda x: x["id"])]
+        meta.thing_classes = thing_classes
+
+        # In COCO, certain category ids are artificially removed,
+        # and by convention they are always ignored.
+        # We deal with COCO's id issue and translate
+        # the category ids to contiguous ids in [0, 80).
+
+        # It works by looking at the "categories" field in the json, therefore
+        # if users' own json also have incontiguous ids, we'll
+        # apply this mapping as well but print a warning.
+        if not (min(cat_ids) == 1 and max(cat_ids) == len(cat_ids)):
+            if "coco" not in dataset_name:
+                logger.warning(
+                    """
+Category ids in annotations are not in [1, #categories]! We'll apply a mapping for you.
+"""
+                )
+        id_map = {v: i for i, v in enumerate(cat_ids)}
+        meta.thing_dataset_id_to_contiguous_id = id_map
+
+    # sort indices for reproducible results
+    img_ids = sorted(coco_api.imgs.keys())
+    # imgs is a list of dicts, each looks something like:
+    # {'license': 4,
+    #  'url': 'http://farm6.staticflickr.com/5454/9413846304_881d5e5c3b_z.jpg',
+    #  'file_name': 'COCO_val2014_000000001268.jpg',
+    #  'height': 427,
+    #  'width': 640,
+    #  'date_captured': '2013-11-17 05:57:24',
+    #  'id': 1268}
+    imgs = coco_api.loadImgs(img_ids)
+    # anns is a list[list[dict]], where each dict is an annotation
+    # record for an object. The inner list enumerates the objects in an image
+    # and the outer list enumerates over images. Example of anns[0]:
+    # [{'segmentation': [[192.81,
+    #     247.09,
+    #     ...
+    #     219.03,
+    #     249.06]],
+    #   'area': 1035.749,
+    #   'iscrowd': 0,
+    #   'image_id': 1268,
+    #   'bbox': [192.81, 224.8, 74.73, 33.43],
+    #   'category_id': 16,
+    #   'id': 42986},
+    #  ...]
+    anns = [coco_api.imgToAnns[img_id] for img_id in img_ids]
+    total_num_valid_anns = sum([len(x) for x in anns])
+    total_num_anns = len(coco_api.anns)
+    if total_num_valid_anns < total_num_anns:
+        logger.warning(
+            f"{json_file} contains {total_num_anns} annotations, but only "
+            f"{total_num_valid_anns} of them match to images in the file."
+        )
+
+    if "minival" not in json_file:
+        # The popular valminusminival & minival annotations for COCO2014 contain this bug.
+        # However the ratio of buggy annotations there is tiny and does not affect accuracy.
+        # Therefore we explicitly white-list them.
+        ann_ids = [ann["id"] for anns_per_image in anns for ann in anns_per_image]
+        assert len(set(ann_ids)) == len(ann_ids), "Annotation ids in '{}' are not unique!".format(
+            json_file
+        )
+
+    imgs_anns = list(zip(imgs, anns))
+    logger.info("Loaded {} images in COCO format from {}".format(len(imgs_anns), json_file))
+
+    dataset_dicts = []
+
+    ann_keys = ["iscrowd", "bbox", "keypoints", "category_id"] + (extra_annotation_keys or [])
+
+    num_instances_without_valid_segmentation = 0
+
+    for img_dict, anno_dict_list in imgs_anns:
+        record = {}
+        record["file_name"] = os.path.join(image_root, img_dict["file_name"])
+        record["height"] = img_dict["height"]
+        record["width"] = img_dict["width"]
+        image_id = record["image_id"] = img_dict["id"]
+
+        objs = []
+        for anno in anno_dict_list:
+            # Check that the image_id in this annotation is the same as
+            # the image_id we're looking at.
+            # This fails only when the data parsing logic or the annotation file is buggy.
+
+            # The original COCO valminusminival2014 & minival2014 annotation files
+            # actually contains bugs that, together with certain ways of using COCO API,
+            # can trigger this assertion.
+            assert anno["image_id"] == image_id
+
+            assert anno.get("ignore", 0) == 0, '"ignore" in COCO json file is not supported.'
+
+            obj = {key: anno[key] for key in ann_keys if key in anno}
+            if "bbox" in obj and len(obj["bbox"]) == 0:
+                raise ValueError(
+                    f"One annotation of image {image_id} contains empty 'bbox' value! "
+                    "This json does not have valid COCO format."
+                )
+
+            segm = anno.get("segmentation", None)
+            if segm:  # either list[list[float]] or dict(RLE)
+                if isinstance(segm, dict):
+                    if isinstance(segm["counts"], list):
+                        # convert to compressed RLE
+                        segm = mask_util.frPyObjects(segm, *segm["size"])
+                else:
+                    # filter out invalid polygons (< 3 points)
+                    segm = [poly for poly in segm if len(poly) % 2 == 0 and len(poly) >= 6]
+                    if len(segm) == 0:
+                        num_instances_without_valid_segmentation += 1
+                        continue  # ignore this instance
+                obj["segmentation"] = segm
+
+            keypts = anno.get("keypoints", None)
+            if keypts:  # list[int]
+                for idx, v in enumerate(keypts):
+                    if idx % 3 != 2:
+                        # COCO's segmentation coordinates are floating points in [0, H or W],
+                        # but keypoint coordinates are integers in [0, H-1 or W-1]
+                        # Therefore we assume the coordinates are "pixel indices" and
+                        # add 0.5 to convert to floating point coordinates.
+                        keypts[idx] = v + 0.5
+                obj["keypoints"] = keypts
+
+            obj["bbox_mode"] = BoxMode.XYWH_ABS
+            if id_map:
+                annotation_category_id = obj["category_id"]
+                try:
+                    obj["category_id"] = id_map[annotation_category_id]
+                except KeyError as e:
+                    raise KeyError(
+                        f"Encountered category_id={annotation_category_id} "
+                        "but this id does not exist in 'categories' of the json file."
+                    ) from e
+            objs.append(obj)
+        record["annotations"] = objs
+        dataset_dicts.append(record)
+
+    if num_instances_without_valid_segmentation > 0:
+        logger.warning(
+            "Filtered out {} instances without valid segmentation. ".format(
+                num_instances_without_valid_segmentation
+            )
+            + "There might be issues in your dataset generation process.  Please "
+            "check https://detectron2.readthedocs.io/en/latest/tutorials/datasets.html carefully"
+        )
+    return dataset_dicts
+
+
+def load_sem_seg(gt_root, image_root, gt_ext="png", image_ext="jpg"):
+    """
+    Load semantic segmentation datasets. All files under "gt_root" with "gt_ext" extension are
+    treated as ground truth annotations and all files under "image_root" with "image_ext" extension
+    as input images. Ground truth and input images are matched using file paths relative to
+    "gt_root" and "image_root" respectively without taking into account file extensions.
+    This works for COCO as well as some other datasets.
+
+    Args:
+        gt_root (str): full path to ground truth semantic segmentation files. Semantic segmentation
+            annotations are stored as images with integer values in pixels that represent
+            corresponding semantic labels.
+        image_root (str): the directory where the input images are.
+        gt_ext (str): file extension for ground truth annotations.
+        image_ext (str): file extension for input images.
+
+    Returns:
+        list[dict]:
+            a list of dicts in detectron2 standard format without instance-level
+            annotation.
+
+    Notes:
+        1. This function does not read the image and ground truth files.
+           The results do not have the "image" and "sem_seg" fields.
+    """
+
+    # We match input images with ground truth based on their relative filepaths (without file
+    # extensions) starting from 'image_root' and 'gt_root' respectively.
+    def file2id(folder_path, file_path):
+        # extract relative path starting from `folder_path`
+        image_id = os.path.normpath(os.path.relpath(file_path, start=folder_path))
+        # remove file extension
+        image_id = os.path.splitext(image_id)[0]
+        return image_id
+
+    input_files = sorted(
+        (os.path.join(image_root, f) for f in PathManager.ls(image_root) if f.endswith(image_ext)),
+        key=lambda file_path: file2id(image_root, file_path),
+    )
+    gt_files = sorted(
+        (os.path.join(gt_root, f) for f in PathManager.ls(gt_root) if f.endswith(gt_ext)),
+        key=lambda file_path: file2id(gt_root, file_path),
+    )
+
+    assert len(gt_files) > 0, "No annotations found in {}.".format(gt_root)
+
+    # Use the intersection, so that val2017_100 annotations can run smoothly with val2017 images
+    if len(input_files) != len(gt_files):
+        logger.warn(
+            "Directory {} and {} has {} and {} files, respectively.".format(
+                image_root, gt_root, len(input_files), len(gt_files)
+            )
+        )
+        input_basenames = [os.path.basename(f)[: -len(image_ext)] for f in input_files]
+        gt_basenames = [os.path.basename(f)[: -len(gt_ext)] for f in gt_files]
+        intersect = list(set(input_basenames) & set(gt_basenames))
+        # sort, otherwise each worker may obtain a list[dict] in different order
+        intersect = sorted(intersect)
+        logger.warn("Will use their intersection of {} files.".format(len(intersect)))
+        input_files = [os.path.join(image_root, f + image_ext) for f in intersect]
+        gt_files = [os.path.join(gt_root, f + gt_ext) for f in intersect]
+
+    logger.info(
+        "Loaded {} images with semantic segmentation from {}".format(len(input_files), image_root)
+    )
+
+    dataset_dicts = []
+    for img_path, gt_path in zip(input_files, gt_files):
+        record = {}
+        record["file_name"] = img_path
+        record["sem_seg_file_name"] = gt_path
+        dataset_dicts.append(record)
+
+    return dataset_dicts
+
+
+def convert_to_coco_dict(dataset_name):
+    """
+    Convert an instance detection/segmentation or keypoint detection dataset
+    in detectron2's standard format into COCO json format.
+
+    Generic dataset description can be found here:
+    https://detectron2.readthedocs.io/tutorials/datasets.html#register-a-dataset
+
+    COCO data format description can be found here:
+    http://cocodataset.org/#format-data
+
+    Args:
+        dataset_name (str):
+            name of the source dataset
+            Must be registered in DatastCatalog and in detectron2's standard format.
+            Must have corresponding metadata "thing_classes"
+    Returns:
+        coco_dict: serializable dict in COCO json format
+    """
+
+    dataset_dicts = DatasetCatalog.get(dataset_name)
+    metadata = MetadataCatalog.get(dataset_name)
+
+    # unmap the category mapping ids for COCO
+    if hasattr(metadata, "thing_dataset_id_to_contiguous_id"):
+        reverse_id_mapping = {v: k for k, v in metadata.thing_dataset_id_to_contiguous_id.items()}
+        reverse_id_mapper = lambda contiguous_id: reverse_id_mapping[contiguous_id]  # noqa
+    else:
+        reverse_id_mapper = lambda contiguous_id: contiguous_id  # noqa
+
+    categories = [
+        {"id": reverse_id_mapper(id), "name": name}
+        for id, name in enumerate(metadata.thing_classes)
+    ]
+
+    logger.info("Converting dataset dicts into COCO format")
+    coco_images = []
+    coco_annotations = []
+
+    for image_id, image_dict in enumerate(dataset_dicts):
+        coco_image = {
+            "id": image_dict.get("image_id", image_id),
+            "width": int(image_dict["width"]),
+            "height": int(image_dict["height"]),
+            "file_name": str(image_dict["file_name"]),
+        }
+        coco_images.append(coco_image)
+
+        anns_per_image = image_dict.get("annotations", [])
+        for annotation in anns_per_image:
+            # create a new dict with only COCO fields
+            coco_annotation = {}
+
+            # COCO requirement: XYWH box format for axis-align and XYWHA for rotated
+            bbox = annotation["bbox"]
+            if isinstance(bbox, np.ndarray):
+                if bbox.ndim != 1:
+                    raise ValueError(f"bbox has to be 1-dimensional. Got shape={bbox.shape}.")
+                bbox = bbox.tolist()
+            if len(bbox) not in [4, 5]:
+                raise ValueError(f"bbox has to has length 4 or 5. Got {bbox}.")
+            from_bbox_mode = annotation["bbox_mode"]
+            to_bbox_mode = BoxMode.XYWH_ABS if len(bbox) == 4 else BoxMode.XYWHA_ABS
+            bbox = BoxMode.convert(bbox, from_bbox_mode, to_bbox_mode)
+
+            # COCO requirement: instance area
+            if "segmentation" in annotation:
+                # Computing areas for instances by counting the pixels
+                segmentation = annotation["segmentation"]
+                # TODO: check segmentation type: RLE, BinaryMask or Polygon
+                if isinstance(segmentation, list):
+                    polygons = PolygonMasks([segmentation])
+                    area = polygons.area()[0].item()
+                elif isinstance(segmentation, dict):  # RLE
+                    area = mask_util.area(segmentation).item()
+                else:
+                    raise TypeError(f"Unknown segmentation type {type(segmentation)}!")
+            else:
+                # Computing areas using bounding boxes
+                if to_bbox_mode == BoxMode.XYWH_ABS:
+                    bbox_xy = BoxMode.convert(bbox, to_bbox_mode, BoxMode.XYXY_ABS)
+                    area = Boxes([bbox_xy]).area()[0].item()
+                else:
+                    area = RotatedBoxes([bbox]).area()[0].item()
+
+            if "keypoints" in annotation:
+                keypoints = annotation["keypoints"]  # list[int]
+                for idx, v in enumerate(keypoints):
+                    if idx % 3 != 2:
+                        # COCO's segmentation coordinates are floating points in [0, H or W],
+                        # but keypoint coordinates are integers in [0, H-1 or W-1]
+                        # For COCO format consistency we substract 0.5
+                        # https://github.com/facebookresearch/detectron2/pull/175#issuecomment-551202163
+                        keypoints[idx] = v - 0.5
+                if "num_keypoints" in annotation:
+                    num_keypoints = annotation["num_keypoints"]
+                else:
+                    num_keypoints = sum(kp > 0 for kp in keypoints[2::3])
+
+            # COCO requirement:
+            #   linking annotations to images
+            #   "id" field must start with 1
+            coco_annotation["id"] = len(coco_annotations) + 1
+            coco_annotation["image_id"] = coco_image["id"]
+            coco_annotation["bbox"] = [round(float(x), 3) for x in bbox]
+            coco_annotation["area"] = float(area)
+            coco_annotation["iscrowd"] = int(annotation.get("iscrowd", 0))
+            coco_annotation["category_id"] = int(reverse_id_mapper(annotation["category_id"]))
+
+            # Add optional fields
+            if "keypoints" in annotation:
+                coco_annotation["keypoints"] = keypoints
+                coco_annotation["num_keypoints"] = num_keypoints
+
+            if "segmentation" in annotation:
+                seg = coco_annotation["segmentation"] = annotation["segmentation"]
+                if isinstance(seg, dict):  # RLE
+                    counts = seg["counts"]
+                    if not isinstance(counts, str):
+                        # make it json-serializable
+                        seg["counts"] = counts.decode("ascii")
+
+            coco_annotations.append(coco_annotation)
+
+    logger.info(
+        "Conversion finished, "
+        f"#images: {len(coco_images)}, #annotations: {len(coco_annotations)}"
+    )
+
+    info = {
+        "date_created": str(datetime.datetime.now()),
+        "description": "Automatically generated COCO json file for Detectron2.",
+    }
+    coco_dict = {
+        "info": info,
+        "images": coco_images,
+        "categories": categories,
+        "licenses": None,
+    }
+    if len(coco_annotations) > 0:
+        coco_dict["annotations"] = coco_annotations
+    return coco_dict
+
+
+def convert_to_coco_json(dataset_name, output_file, allow_cached=True):
+    """
+    Converts dataset into COCO format and saves it to a json file.
+    dataset_name must be registered in DatasetCatalog and in detectron2's standard format.
+
+    Args:
+        dataset_name:
+            reference from the config file to the catalogs
+            must be registered in DatasetCatalog and in detectron2's standard format
+        output_file: path of json file that will be saved to
+        allow_cached: if json file is already present then skip conversion
+    """
+
+    # TODO: The dataset or the conversion script *may* change,
+    # a checksum would be useful for validating the cached data
+
+    PathManager.mkdirs(os.path.dirname(output_file))
+    with file_lock(output_file):
+        if PathManager.exists(output_file) and allow_cached:
+            logger.warning(
+                f"Using previously cached COCO format annotations at '{output_file}'. "
+                "You need to clear the cache file if your dataset has been modified."
+            )
+        else:
+            logger.info(f"Converting annotations of dataset '{dataset_name}' to COCO format ...)")
+            coco_dict = convert_to_coco_dict(dataset_name)
+
+            logger.info(f"Caching COCO format annotations at '{output_file}' ...")
+            tmp_file = output_file + ".tmp"
+            with PathManager.open(tmp_file, "w") as f:
+                json.dump(coco_dict, f)
+            shutil.move(tmp_file, output_file)
+
+
+def register_coco_instances(name, metadata, json_file, image_root):
+    """
+    Register a dataset in COCO's json annotation format for
+    instance detection, instance segmentation and keypoint detection.
+    (i.e., Type 1 and 2 in http://cocodataset.org/#format-data.
+    `instances*.json` and `person_keypoints*.json` in the dataset).
+
+    This is an example of how to register a new dataset.
+    You can do something similar to this function, to register new datasets.
+
+    Args:
+        name (str): the name that identifies a dataset, e.g. "coco_2014_train".
+        metadata (dict): extra metadata associated with this dataset.  You can
+            leave it as an empty dict.
+        json_file (str): path to the json instance annotation file.
+        image_root (str or path-like): directory which contains all the images.
+    """
+    assert isinstance(name, str), name
+    assert isinstance(json_file, (str, os.PathLike)), json_file
+    assert isinstance(image_root, (str, os.PathLike)), image_root
+    # 1. register a function which returns dicts
+    DatasetCatalog.register(name, lambda: load_coco_json(json_file, image_root, name))
+
+    # 2. Optionally, add metadata about this dataset,
+    # since they might be useful in evaluation, visualization or logging
+    MetadataCatalog.get(name).set(
+        json_file=json_file, image_root=image_root, evaluator_type="coco", **metadata
+    )
+
+
+def main() -> None:
+    global logger
+    """
+    Test the COCO json dataset loader.
+
+    Usage:
+        python -m detectron2.data.datasets.coco \
+            path/to/json path/to/image_root dataset_name
+
+        "dataset_name" can be "coco_2014_minival_100", or other
+        pre-registered ones
+    """
+    import sys
+
+    import detectron2.data.datasets  # noqa  # add pre-defined metadata
+    from detectron2.utils.logger import setup_logger
+    from detectron2.utils.visualizer import Visualizer
+
+    logger = setup_logger(name=__name__)
+    assert sys.argv[3] in DatasetCatalog.list()
+    meta = MetadataCatalog.get(sys.argv[3])
+
+    dicts = load_coco_json(sys.argv[1], sys.argv[2], sys.argv[3])
+    logger.info("Done loading {} samples.".format(len(dicts)))
+
+    dirname = "coco-data-vis"
+    os.makedirs(dirname, exist_ok=True)
+    for d in dicts:
+        img = np.array(Image.open(d["file_name"]))
+        visualizer = Visualizer(img, metadata=meta)
+        vis = visualizer.draw_dataset_dict(d)
+        fpath = os.path.join(dirname, os.path.basename(d["file_name"]))
+        vis.save(fpath)
+
+
+if __name__ == "__main__":
+    main()  # pragma: no cover

detectron2/data/datasets/coco_panoptic.py

@@ -0,0 +1,228 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import copy
+import json
+import os
+
+from detectron2.data import DatasetCatalog, MetadataCatalog
+from detectron2.utils.file_io import PathManager
+
+from .coco import load_coco_json, load_sem_seg
+
+__all__ = ["register_coco_panoptic", "register_coco_panoptic_separated"]
+
+
+def load_coco_panoptic_json(json_file, image_dir, gt_dir, meta):
+    """
+    Args:
+        image_dir (str): path to the raw dataset. e.g., "~/coco/train2017".
+        gt_dir (str): path to the raw annotations. e.g., "~/coco/panoptic_train2017".
+        json_file (str): path to the json file. e.g., "~/coco/annotations/panoptic_train2017.json".
+
+    Returns:
+        list[dict]: a list of dicts in Detectron2 standard format. (See
+        `Using Custom Datasets </tutorials/datasets.html>`_ )
+    """
+
+    def _convert_category_id(segment_info, meta):
+        if segment_info["category_id"] in meta["thing_dataset_id_to_contiguous_id"]:
+            segment_info["category_id"] = meta["thing_dataset_id_to_contiguous_id"][
+                segment_info["category_id"]
+            ]
+            segment_info["isthing"] = True
+        else:
+            segment_info["category_id"] = meta["stuff_dataset_id_to_contiguous_id"][
+                segment_info["category_id"]
+            ]
+            segment_info["isthing"] = False
+        return segment_info
+
+    with PathManager.open(json_file) as f:
+        json_info = json.load(f)
+
+    ret = []
+    for ann in json_info["annotations"]:
+        image_id = int(ann["image_id"])
+        # TODO: currently we assume image and label has the same filename but
+        # different extension, and images have extension ".jpg" for COCO. Need
+        # to make image extension a user-provided argument if we extend this
+        # function to support other COCO-like datasets.
+        image_file = os.path.join(image_dir, os.path.splitext(ann["file_name"])[0] + ".jpg")
+        label_file = os.path.join(gt_dir, ann["file_name"])
+        segments_info = [_convert_category_id(x, meta) for x in ann["segments_info"]]
+        ret.append(
+            {
+                "file_name": image_file,
+                "image_id": image_id,
+                "pan_seg_file_name": label_file,
+                "segments_info": segments_info,
+            }
+        )
+    assert len(ret), f"No images found in {image_dir}!"
+    assert PathManager.isfile(ret[0]["file_name"]), ret[0]["file_name"]
+    assert PathManager.isfile(ret[0]["pan_seg_file_name"]), ret[0]["pan_seg_file_name"]
+    return ret
+
+
+def register_coco_panoptic(
+    name, metadata, image_root, panoptic_root, panoptic_json, instances_json=None
+):
+    """
+    Register a "standard" version of COCO panoptic segmentation dataset named `name`.
+    The dictionaries in this registered dataset follows detectron2's standard format.
+    Hence it's called "standard".
+
+    Args:
+        name (str): the name that identifies a dataset,
+            e.g. "coco_2017_train_panoptic"
+        metadata (dict): extra metadata associated with this dataset.
+        image_root (str): directory which contains all the images
+        panoptic_root (str): directory which contains panoptic annotation images in COCO format
+        panoptic_json (str): path to the json panoptic annotation file in COCO format
+        sem_seg_root (none): not used, to be consistent with
+            `register_coco_panoptic_separated`.
+        instances_json (str): path to the json instance annotation file
+    """
+    panoptic_name = name
+    DatasetCatalog.register(
+        panoptic_name,
+        lambda: load_coco_panoptic_json(panoptic_json, image_root, panoptic_root, metadata),
+    )
+    MetadataCatalog.get(panoptic_name).set(
+        panoptic_root=panoptic_root,
+        image_root=image_root,
+        panoptic_json=panoptic_json,
+        json_file=instances_json,
+        evaluator_type="coco_panoptic_seg",
+        ignore_label=255,
+        label_divisor=1000,
+        **metadata,
+    )
+
+
+def register_coco_panoptic_separated(
+    name, metadata, image_root, panoptic_root, panoptic_json, sem_seg_root, instances_json
+):
+    """
+    Register a "separated" version of COCO panoptic segmentation dataset named `name`.
+    The annotations in this registered dataset will contain both instance annotations and
+    semantic annotations, each with its own contiguous ids. Hence it's called "separated".
+
+    It follows the setting used by the PanopticFPN paper:
+
+    1. The instance annotations directly come from polygons in the COCO
+       instances annotation task, rather than from the masks in the COCO panoptic annotations.
+
+       The two format have small differences:
+       Polygons in the instance annotations may have overlaps.
+       The mask annotations are produced by labeling the overlapped polygons
+       with depth ordering.
+
+    2. The semantic annotations are converted from panoptic annotations, where
+       all "things" are assigned a semantic id of 0.
+       All semantic categories will therefore have ids in contiguous
+       range [1, #stuff_categories].
+
+    This function will also register a pure semantic segmentation dataset
+    named ``name + '_stuffonly'``.
+
+    Args:
+        name (str): the name that identifies a dataset,
+            e.g. "coco_2017_train_panoptic"
+        metadata (dict): extra metadata associated with this dataset.
+        image_root (str): directory which contains all the images
+        panoptic_root (str): directory which contains panoptic annotation images
+        panoptic_json (str): path to the json panoptic annotation file
+        sem_seg_root (str): directory which contains all the ground truth segmentation annotations.
+        instances_json (str): path to the json instance annotation file
+    """
+    panoptic_name = name + "_separated"
+    DatasetCatalog.register(
+        panoptic_name,
+        lambda: merge_to_panoptic(
+            load_coco_json(instances_json, image_root, panoptic_name),
+            load_sem_seg(sem_seg_root, image_root),
+        ),
+    )
+    MetadataCatalog.get(panoptic_name).set(
+        panoptic_root=panoptic_root,
+        image_root=image_root,
+        panoptic_json=panoptic_json,
+        sem_seg_root=sem_seg_root,
+        json_file=instances_json,  # TODO rename
+        evaluator_type="coco_panoptic_seg",
+        ignore_label=255,
+        **metadata,
+    )
+
+    semantic_name = name + "_stuffonly"
+    DatasetCatalog.register(semantic_name, lambda: load_sem_seg(sem_seg_root, image_root))
+    MetadataCatalog.get(semantic_name).set(
+        sem_seg_root=sem_seg_root,
+        image_root=image_root,
+        evaluator_type="sem_seg",
+        ignore_label=255,
+        **metadata,
+    )
+
+
+def merge_to_panoptic(detection_dicts, sem_seg_dicts):
+    """
+    Create dataset dicts for panoptic segmentation, by
+    merging two dicts using "file_name" field to match their entries.
+
+    Args:
+        detection_dicts (list[dict]): lists of dicts for object detection or instance segmentation.
+        sem_seg_dicts (list[dict]): lists of dicts for semantic segmentation.
+
+    Returns:
+        list[dict] (one per input image): Each dict contains all (key, value) pairs from dicts in
+            both detection_dicts and sem_seg_dicts that correspond to the same image.
+            The function assumes that the same key in different dicts has the same value.
+    """
+    results = []
+    sem_seg_file_to_entry = {x["file_name"]: x for x in sem_seg_dicts}
+    assert len(sem_seg_file_to_entry) > 0
+
+    for det_dict in detection_dicts:
+        dic = copy.copy(det_dict)
+        dic.update(sem_seg_file_to_entry[dic["file_name"]])
+        results.append(dic)
+    return results
+
+
+if __name__ == "__main__":
+    """
+    Test the COCO panoptic dataset loader.
+
+    Usage:
+        python -m detectron2.data.datasets.coco_panoptic \
+            path/to/image_root path/to/panoptic_root path/to/panoptic_json dataset_name 10
+
+        "dataset_name" can be "coco_2017_train_panoptic", or other
+        pre-registered ones
+    """
+    from detectron2.utils.logger import setup_logger
+    from detectron2.utils.visualizer import Visualizer
+    import detectron2.data.datasets  # noqa # add pre-defined metadata
+    import sys
+    from PIL import Image
+    import numpy as np
+
+    logger = setup_logger(name=__name__)
+    assert sys.argv[4] in DatasetCatalog.list()
+    meta = MetadataCatalog.get(sys.argv[4])
+
+    dicts = load_coco_panoptic_json(sys.argv[3], sys.argv[1], sys.argv[2], meta.as_dict())
+    logger.info("Done loading {} samples.".format(len(dicts)))
+
+    dirname = "coco-data-vis"
+    os.makedirs(dirname, exist_ok=True)
+    num_imgs_to_vis = int(sys.argv[5])
+    for i, d in enumerate(dicts):
+        img = np.array(Image.open(d["file_name"]))
+        visualizer = Visualizer(img, metadata=meta)
+        vis = visualizer.draw_dataset_dict(d)
+        fpath = os.path.join(dirname, os.path.basename(d["file_name"]))
+        vis.save(fpath)
+        if i + 1 >= num_imgs_to_vis:
+            break

detectron2/data/datasets/lvis.py

@@ -0,0 +1,250 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import logging
+import os
+from fvcore.common.timer import Timer
+
+from detectron2.data import DatasetCatalog, MetadataCatalog
+from detectron2.structures import BoxMode
+from detectron2.utils.file_io import PathManager
+
+from .builtin_meta import _get_coco_instances_meta
+from .lvis_v0_5_categories import LVIS_CATEGORIES as LVIS_V0_5_CATEGORIES
+from .lvis_v1_categories import LVIS_CATEGORIES as LVIS_V1_CATEGORIES
+from .lvis_v1_category_image_count import LVIS_CATEGORY_IMAGE_COUNT as LVIS_V1_CATEGORY_IMAGE_COUNT
+
+"""
+This file contains functions to parse LVIS-format annotations into dicts in the
+"Detectron2 format".
+"""
+
+logger = logging.getLogger(__name__)
+
+__all__ = ["load_lvis_json", "register_lvis_instances", "get_lvis_instances_meta"]
+
+
+def register_lvis_instances(name, metadata, json_file, image_root):
+    """
+    Register a dataset in LVIS's json annotation format for instance detection and segmentation.
+
+    Args:
+        name (str): a name that identifies the dataset, e.g. "lvis_v0.5_train".
+        metadata (dict): extra metadata associated with this dataset. It can be an empty dict.
+        json_file (str): path to the json instance annotation file.
+        image_root (str or path-like): directory which contains all the images.
+    """
+    DatasetCatalog.register(name, lambda: load_lvis_json(json_file, image_root, name))
+    MetadataCatalog.get(name).set(
+        json_file=json_file, image_root=image_root, evaluator_type="lvis", **metadata
+    )
+
+
+def load_lvis_json(json_file, image_root, dataset_name=None, extra_annotation_keys=None):
+    """
+    Load a json file in LVIS's annotation format.
+
+    Args:
+        json_file (str): full path to the LVIS json annotation file.
+        image_root (str): the directory where the images in this json file exists.
+        dataset_name (str): the name of the dataset (e.g., "lvis_v0.5_train").
+            If provided, this function will put "thing_classes" into the metadata
+            associated with this dataset.
+        extra_annotation_keys (list[str]): list of per-annotation keys that should also be
+            loaded into the dataset dict (besides "bbox", "bbox_mode", "category_id",
+            "segmentation"). The values for these keys will be returned as-is.
+
+    Returns:
+        list[dict]: a list of dicts in Detectron2 standard format. (See
+        `Using Custom Datasets </tutorials/datasets.html>`_ )
+
+    Notes:
+        1. This function does not read the image files.
+           The results do not have the "image" field.
+    """
+    from lvis import LVIS
+
+    json_file = PathManager.get_local_path(json_file)
+
+    timer = Timer()
+    lvis_api = LVIS(json_file)
+    if timer.seconds() > 1:
+        logger.info("Loading {} takes {:.2f} seconds.".format(json_file, timer.seconds()))
+
+    if dataset_name is not None:
+        meta = get_lvis_instances_meta(dataset_name)
+        MetadataCatalog.get(dataset_name).set(**meta)
+
+    # sort indices for reproducible results
+    img_ids = sorted(lvis_api.imgs.keys())
+    # imgs is a list of dicts, each looks something like:
+    # {'license': 4,
+    #  'url': 'http://farm6.staticflickr.com/5454/9413846304_881d5e5c3b_z.jpg',
+    #  'file_name': 'COCO_val2014_000000001268.jpg',
+    #  'height': 427,
+    #  'width': 640,
+    #  'date_captured': '2013-11-17 05:57:24',
+    #  'id': 1268}
+    imgs = lvis_api.load_imgs(img_ids)
+    # anns is a list[list[dict]], where each dict is an annotation
+    # record for an object. The inner list enumerates the objects in an image
+    # and the outer list enumerates over images. Example of anns[0]:
+    # [{'segmentation': [[192.81,
+    #     247.09,
+    #     ...
+    #     219.03,
+    #     249.06]],
+    #   'area': 1035.749,
+    #   'image_id': 1268,
+    #   'bbox': [192.81, 224.8, 74.73, 33.43],
+    #   'category_id': 16,
+    #   'id': 42986},
+    #  ...]
+    anns = [lvis_api.img_ann_map[img_id] for img_id in img_ids]
+
+    # Sanity check that each annotation has a unique id
+    ann_ids = [ann["id"] for anns_per_image in anns for ann in anns_per_image]
+    assert len(set(ann_ids)) == len(ann_ids), "Annotation ids in '{}' are not unique".format(
+        json_file
+    )
+
+    imgs_anns = list(zip(imgs, anns))
+
+    logger.info("Loaded {} images in the LVIS format from {}".format(len(imgs_anns), json_file))
+
+    if extra_annotation_keys:
+        logger.info(
+            "The following extra annotation keys will be loaded: {} ".format(extra_annotation_keys)
+        )
+    else:
+        extra_annotation_keys = []
+
+    def get_file_name(img_root, img_dict):
+        # Determine the path including the split folder ("train2017", "val2017", "test2017") from
+        # the coco_url field. Example:
+        #   'coco_url': 'http://images.cocodataset.org/train2017/000000155379.jpg'
+        split_folder, file_name = img_dict["coco_url"].split("/")[-2:]
+        return os.path.join(img_root + split_folder, file_name)
+
+    dataset_dicts = []
+
+    for img_dict, anno_dict_list in imgs_anns:
+        record = {}
+        record["file_name"] = get_file_name(image_root, img_dict)
+        record["height"] = img_dict["height"]
+        record["width"] = img_dict["width"]
+        record["not_exhaustive_category_ids"] = img_dict.get("not_exhaustive_category_ids", [])
+        record["neg_category_ids"] = img_dict.get("neg_category_ids", [])
+        image_id = record["image_id"] = img_dict["id"]
+
+        objs = []
+        for anno in anno_dict_list:
+            # Check that the image_id in this annotation is the same as
+            # the image_id we're looking at.
+            # This fails only when the data parsing logic or the annotation file is buggy.
+            assert anno["image_id"] == image_id
+            obj = {"bbox": anno["bbox"], "bbox_mode": BoxMode.XYWH_ABS}
+            # LVIS data loader can be used to load COCO dataset categories. In this case `meta`
+            # variable will have a field with COCO-specific category mapping.
+            if dataset_name is not None and "thing_dataset_id_to_contiguous_id" in meta:
+                obj["category_id"] = meta["thing_dataset_id_to_contiguous_id"][anno["category_id"]]
+            else:
+                obj["category_id"] = anno["category_id"] - 1  # Convert 1-indexed to 0-indexed
+            segm = anno["segmentation"]  # list[list[float]]
+            # filter out invalid polygons (< 3 points)
+            valid_segm = [poly for poly in segm if len(poly) % 2 == 0 and len(poly) >= 6]
+            assert len(segm) == len(
+                valid_segm
+            ), "Annotation contains an invalid polygon with < 3 points"
+            assert len(segm) > 0
+            obj["segmentation"] = segm
+            for extra_ann_key in extra_annotation_keys:
+                obj[extra_ann_key] = anno[extra_ann_key]
+            objs.append(obj)
+        record["annotations"] = objs
+        dataset_dicts.append(record)
+
+    return dataset_dicts
+
+
+def get_lvis_instances_meta(dataset_name):
+    """
+    Load LVIS metadata.
+
+    Args:
+        dataset_name (str): LVIS dataset name without the split name (e.g., "lvis_v0.5").
+
+    Returns:
+        dict: LVIS metadata with keys: thing_classes
+    """
+    if "cocofied" in dataset_name:
+        return _get_coco_instances_meta()
+    if "v0.5" in dataset_name:
+        return _get_lvis_instances_meta_v0_5()
+    elif "v1" in dataset_name:
+        return _get_lvis_instances_meta_v1()
+    raise ValueError("No built-in metadata for dataset {}".format(dataset_name))
+
+
+def _get_lvis_instances_meta_v0_5():
+    assert len(LVIS_V0_5_CATEGORIES) == 1230
+    cat_ids = [k["id"] for k in LVIS_V0_5_CATEGORIES]
+    assert min(cat_ids) == 1 and max(cat_ids) == len(
+        cat_ids
+    ), "Category ids are not in [1, #categories], as expected"
+    # Ensure that the category list is sorted by id
+    lvis_categories = sorted(LVIS_V0_5_CATEGORIES, key=lambda x: x["id"])
+    thing_classes = [k["synonyms"][0] for k in lvis_categories]
+    meta = {"thing_classes": thing_classes}
+    return meta
+
+
+def _get_lvis_instances_meta_v1():
+    assert len(LVIS_V1_CATEGORIES) == 1203
+    cat_ids = [k["id"] for k in LVIS_V1_CATEGORIES]
+    assert min(cat_ids) == 1 and max(cat_ids) == len(
+        cat_ids
+    ), "Category ids are not in [1, #categories], as expected"
+    # Ensure that the category list is sorted by id
+    lvis_categories = sorted(LVIS_V1_CATEGORIES, key=lambda x: x["id"])
+    thing_classes = [k["synonyms"][0] for k in lvis_categories]
+    meta = {
+        "thing_classes": thing_classes,
+        "class_image_count": LVIS_V1_CATEGORY_IMAGE_COUNT,
+    }
+    return meta
+
+
+def main() -> None:
+    global logger
+    """
+    Test the LVIS json dataset loader.
+
+    Usage:
+        python -m detectron2.data.datasets.lvis \
+            path/to/json path/to/image_root dataset_name vis_limit
+    """
+    import sys
+
+    import detectron2.data.datasets  # noqa  # add pre-defined metadata
+    import numpy as np
+    from detectron2.utils.logger import setup_logger
+    from detectron2.utils.visualizer import Visualizer
+    from PIL import Image
+
+    logger = setup_logger(name=__name__)
+    meta = MetadataCatalog.get(sys.argv[3])
+
+    dicts = load_lvis_json(sys.argv[1], sys.argv[2], sys.argv[3])
+    logger.info("Done loading {} samples.".format(len(dicts)))
+
+    dirname = "lvis-data-vis"
+    os.makedirs(dirname, exist_ok=True)
+    for d in dicts[: int(sys.argv[4])]:
+        img = np.array(Image.open(d["file_name"]))
+        visualizer = Visualizer(img, metadata=meta)
+        vis = visualizer.draw_dataset_dict(d)
+        fpath = os.path.join(dirname, os.path.basename(d["file_name"]))
+        vis.save(fpath)
+
+
+if __name__ == "__main__":
+    main()  # pragma: no cover

detectron2/data/datasets/lvis_v1_category_image_count.py

@@ -0,0 +1,20 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+# Autogen with
+# with open("lvis_v1_train.json", "r") as f:
+#     a = json.load(f)
+# c = a["categories"]
+# for x in c:
+# del x["name"]
+# del x["instance_count"]
+# del x["def"]
+# del x["synonyms"]
+# del x["frequency"]
+# del x["synset"]
+# LVIS_CATEGORY_IMAGE_COUNT = repr(c) + "  # noqa"
+# with open("/tmp/lvis_category_image_count.py", "wt") as f:
+#     f.write(f"LVIS_CATEGORY_IMAGE_COUNT = {LVIS_CATEGORY_IMAGE_COUNT}")
+# Then paste the contents of that file below
+
+# fmt: off
+LVIS_CATEGORY_IMAGE_COUNT = [{'id': 1, 'image_count': 64}, {'id': 2, 'image_count': 364}, {'id': 3, 'image_count': 1911}, {'id': 4, 'image_count': 149}, {'id': 5, 'image_count': 29}, {'id': 6, 'image_count': 26}, {'id': 7, 'image_count': 59}, {'id': 8, 'image_count': 22}, {'id': 9, 'image_count': 12}, {'id': 10, 'image_count': 28}, {'id': 11, 'image_count': 505}, {'id': 12, 'image_count': 1207}, {'id': 13, 'image_count': 4}, {'id': 14, 'image_count': 10}, {'id': 15, 'image_count': 500}, {'id': 16, 'image_count': 33}, {'id': 17, 'image_count': 3}, {'id': 18, 'image_count': 44}, {'id': 19, 'image_count': 561}, {'id': 20, 'image_count': 8}, {'id': 21, 'image_count': 9}, {'id': 22, 'image_count': 33}, {'id': 23, 'image_count': 1883}, {'id': 24, 'image_count': 98}, {'id': 25, 'image_count': 70}, {'id': 26, 'image_count': 46}, {'id': 27, 'image_count': 117}, {'id': 28, 'image_count': 41}, {'id': 29, 'image_count': 1395}, {'id': 30, 'image_count': 7}, {'id': 31, 'image_count': 1}, {'id': 32, 'image_count': 314}, {'id': 33, 'image_count': 31}, {'id': 34, 'image_count': 1905}, {'id': 35, 'image_count': 1859}, {'id': 36, 'image_count': 1623}, {'id': 37, 'image_count': 47}, {'id': 38, 'image_count': 3}, {'id': 39, 'image_count': 3}, {'id': 40, 'image_count': 1}, {'id': 41, 'image_count': 305}, {'id': 42, 'image_count': 6}, {'id': 43, 'image_count': 210}, {'id': 44, 'image_count': 36}, {'id': 45, 'image_count': 1787}, {'id': 46, 'image_count': 17}, {'id': 47, 'image_count': 51}, {'id': 48, 'image_count': 138}, {'id': 49, 'image_count': 3}, {'id': 50, 'image_count': 1470}, {'id': 51, 'image_count': 3}, {'id': 52, 'image_count': 2}, {'id': 53, 'image_count': 186}, {'id': 54, 'image_count': 76}, {'id': 55, 'image_count': 26}, {'id': 56, 'image_count': 303}, {'id': 57, 'image_count': 738}, {'id': 58, 'image_count': 1799}, {'id': 59, 'image_count': 1934}, {'id': 60, 'image_count': 1609}, {'id': 61, 'image_count': 1622}, {'id': 62, 'image_count': 41}, {'id': 63, 'image_count': 4}, {'id': 64, 'image_count': 11}, {'id': 65, 'image_count': 270}, {'id': 66, 'image_count': 349}, {'id': 67, 'image_count': 42}, {'id': 68, 'image_count': 823}, {'id': 69, 'image_count': 6}, {'id': 70, 'image_count': 48}, {'id': 71, 'image_count': 3}, {'id': 72, 'image_count': 42}, {'id': 73, 'image_count': 24}, {'id': 74, 'image_count': 16}, {'id': 75, 'image_count': 605}, {'id': 76, 'image_count': 646}, {'id': 77, 'image_count': 1765}, {'id': 78, 'image_count': 2}, {'id': 79, 'image_count': 125}, {'id': 80, 'image_count': 1420}, {'id': 81, 'image_count': 140}, {'id': 82, 'image_count': 4}, {'id': 83, 'image_count': 322}, {'id': 84, 'image_count': 60}, {'id': 85, 'image_count': 2}, {'id': 86, 'image_count': 231}, {'id': 87, 'image_count': 333}, {'id': 88, 'image_count': 1941}, {'id': 89, 'image_count': 367}, {'id': 90, 'image_count': 1922}, {'id': 91, 'image_count': 18}, {'id': 92, 'image_count': 81}, {'id': 93, 'image_count': 1}, {'id': 94, 'image_count': 1852}, {'id': 95, 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'image_count': 16}, {'id': 964, 'image_count': 1926}, {'id': 965, 'image_count': 1789}, {'id': 966, 'image_count': 401}, {'id': 967, 'image_count': 1968}, {'id': 968, 'image_count': 1167}, {'id': 969, 'image_count': 1}, {'id': 970, 'image_count': 56}, {'id': 971, 'image_count': 17}, {'id': 972, 'image_count': 1}, {'id': 973, 'image_count': 58}, {'id': 974, 'image_count': 9}, {'id': 975, 'image_count': 8}, {'id': 976, 'image_count': 1124}, {'id': 977, 'image_count': 31}, {'id': 978, 'image_count': 16}, {'id': 979, 'image_count': 491}, {'id': 980, 'image_count': 432}, {'id': 981, 'image_count': 1945}, {'id': 982, 'image_count': 1899}, {'id': 983, 'image_count': 5}, {'id': 984, 'image_count': 28}, {'id': 985, 'image_count': 7}, {'id': 986, 'image_count': 146}, {'id': 987, 'image_count': 1}, {'id': 988, 'image_count': 25}, {'id': 989, 'image_count': 22}, {'id': 990, 'image_count': 1}, {'id': 991, 'image_count': 10}, {'id': 992, 'image_count': 9}, {'id': 993, 'image_count': 308}, {'id': 994, 'image_count': 4}, {'id': 995, 'image_count': 1969}, {'id': 996, 'image_count': 45}, {'id': 997, 'image_count': 12}, {'id': 998, 'image_count': 1}, {'id': 999, 'image_count': 85}, {'id': 1000, 'image_count': 1127}, {'id': 1001, 'image_count': 11}, {'id': 1002, 'image_count': 60}, {'id': 1003, 'image_count': 1}, {'id': 1004, 'image_count': 16}, {'id': 1005, 'image_count': 1}, {'id': 1006, 'image_count': 65}, {'id': 1007, 'image_count': 13}, {'id': 1008, 'image_count': 655}, {'id': 1009, 'image_count': 51}, {'id': 1010, 'image_count': 1}, {'id': 1011, 'image_count': 673}, {'id': 1012, 'image_count': 5}, {'id': 1013, 'image_count': 36}, {'id': 1014, 'image_count': 54}, {'id': 1015, 'image_count': 5}, {'id': 1016, 'image_count': 8}, {'id': 1017, 'image_count': 305}, {'id': 1018, 'image_count': 297}, {'id': 1019, 'image_count': 1053}, {'id': 1020, 'image_count': 223}, {'id': 1021, 'image_count': 1037}, {'id': 1022, 'image_count': 63}, {'id': 1023, 'image_count': 1881}, {'id': 1024, 'image_count': 507}, {'id': 1025, 'image_count': 333}, {'id': 1026, 'image_count': 1911}, {'id': 1027, 'image_count': 1765}, {'id': 1028, 'image_count': 1}, {'id': 1029, 'image_count': 5}, {'id': 1030, 'image_count': 1}, {'id': 1031, 'image_count': 9}, {'id': 1032, 'image_count': 2}, {'id': 1033, 'image_count': 151}, {'id': 1034, 'image_count': 82}, {'id': 1035, 'image_count': 1931}, {'id': 1036, 'image_count': 41}, {'id': 1037, 'image_count': 1895}, {'id': 1038, 'image_count': 24}, {'id': 1039, 'image_count': 22}, {'id': 1040, 'image_count': 35}, {'id': 1041, 'image_count': 69}, {'id': 1042, 'image_count': 962}, {'id': 1043, 'image_count': 588}, {'id': 1044, 'image_count': 21}, {'id': 1045, 'image_count': 825}, {'id': 1046, 'image_count': 52}, {'id': 1047, 'image_count': 5}, {'id': 1048, 'image_count': 5}, {'id': 1049, 'image_count': 5}, {'id': 1050, 'image_count': 1860}, {'id': 1051, 'image_count': 56}, {'id': 1052, 'image_count': 1582}, {'id': 1053, 'image_count': 7}, {'id': 1054, 'image_count': 2}, {'id': 1055, 'image_count': 1562}, {'id': 1056, 'image_count': 1885}, {'id': 1057, 'image_count': 1}, {'id': 1058, 'image_count': 5}, {'id': 1059, 'image_count': 137}, {'id': 1060, 'image_count': 1094}, {'id': 1061, 'image_count': 134}, {'id': 1062, 'image_count': 29}, {'id': 1063, 'image_count': 22}, {'id': 1064, 'image_count': 522}, {'id': 1065, 'image_count': 50}, {'id': 1066, 'image_count': 68}, {'id': 1067, 'image_count': 16}, {'id': 1068, 'image_count': 40}, {'id': 1069, 'image_count': 35}, {'id': 1070, 'image_count': 135}, {'id': 1071, 'image_count': 1413}, {'id': 1072, 'image_count': 772}, {'id': 1073, 'image_count': 50}, {'id': 1074, 'image_count': 1015}, {'id': 1075, 'image_count': 1}, {'id': 1076, 'image_count': 65}, {'id': 1077, 'image_count': 1900}, {'id': 1078, 'image_count': 1302}, {'id': 1079, 'image_count': 1977}, {'id': 1080, 'image_count': 2}, {'id': 1081, 'image_count': 29}, {'id': 1082, 'image_count': 36}, {'id': 1083, 'image_count': 138}, {'id': 1084, 'image_count': 4}, {'id': 1085, 'image_count': 67}, {'id': 1086, 'image_count': 26}, {'id': 1087, 'image_count': 25}, {'id': 1088, 'image_count': 33}, {'id': 1089, 'image_count': 37}, {'id': 1090, 'image_count': 50}, {'id': 1091, 'image_count': 270}, {'id': 1092, 'image_count': 12}, {'id': 1093, 'image_count': 316}, {'id': 1094, 'image_count': 41}, {'id': 1095, 'image_count': 224}, {'id': 1096, 'image_count': 105}, {'id': 1097, 'image_count': 1925}, {'id': 1098, 'image_count': 1021}, {'id': 1099, 'image_count': 1213}, {'id': 1100, 'image_count': 172}, {'id': 1101, 'image_count': 28}, {'id': 1102, 'image_count': 745}, {'id': 1103, 'image_count': 187}, {'id': 1104, 'image_count': 147}, {'id': 1105, 'image_count': 136}, {'id': 1106, 'image_count': 34}, {'id': 1107, 'image_count': 41}, {'id': 1108, 'image_count': 636}, {'id': 1109, 'image_count': 570}, {'id': 1110, 'image_count': 1149}, {'id': 1111, 'image_count': 61}, {'id': 1112, 'image_count': 1890}, {'id': 1113, 'image_count': 18}, {'id': 1114, 'image_count': 143}, {'id': 1115, 'image_count': 1517}, {'id': 1116, 'image_count': 7}, {'id': 1117, 'image_count': 943}, {'id': 1118, 'image_count': 6}, {'id': 1119, 'image_count': 1}, {'id': 1120, 'image_count': 11}, {'id': 1121, 'image_count': 101}, {'id': 1122, 'image_count': 1909}, {'id': 1123, 'image_count': 800}, {'id': 1124, 'image_count': 1}, {'id': 1125, 'image_count': 44}, {'id': 1126, 'image_count': 3}, {'id': 1127, 'image_count': 44}, {'id': 1128, 'image_count': 31}, {'id': 1129, 'image_count': 7}, {'id': 1130, 'image_count': 20}, {'id': 1131, 'image_count': 11}, {'id': 1132, 'image_count': 13}, {'id': 1133, 'image_count': 1924}, {'id': 1134, 'image_count': 113}, {'id': 1135, 'image_count': 2}, {'id': 1136, 'image_count': 139}, {'id': 1137, 'image_count': 12}, {'id': 1138, 'image_count': 37}, {'id': 1139, 'image_count': 1866}, {'id': 1140, 'image_count': 47}, {'id': 1141, 'image_count': 1468}, {'id': 1142, 'image_count': 729}, {'id': 1143, 'image_count': 24}, {'id': 1144, 'image_count': 1}, {'id': 1145, 'image_count': 10}, {'id': 1146, 'image_count': 3}, {'id': 1147, 'image_count': 14}, {'id': 1148, 'image_count': 4}, {'id': 1149, 'image_count': 29}, {'id': 1150, 'image_count': 4}, {'id': 1151, 'image_count': 70}, {'id': 1152, 'image_count': 46}, {'id': 1153, 'image_count': 14}, {'id': 1154, 'image_count': 48}, {'id': 1155, 'image_count': 1855}, {'id': 1156, 'image_count': 113}, {'id': 1157, 'image_count': 1}, {'id': 1158, 'image_count': 1}, {'id': 1159, 'image_count': 10}, {'id': 1160, 'image_count': 54}, {'id': 1161, 'image_count': 1923}, {'id': 1162, 'image_count': 630}, {'id': 1163, 'image_count': 31}, {'id': 1164, 'image_count': 69}, {'id': 1165, 'image_count': 7}, {'id': 1166, 'image_count': 11}, {'id': 1167, 'image_count': 1}, {'id': 1168, 'image_count': 30}, {'id': 1169, 'image_count': 50}, {'id': 1170, 'image_count': 45}, {'id': 1171, 'image_count': 28}, {'id': 1172, 'image_count': 114}, {'id': 1173, 'image_count': 193}, {'id': 1174, 'image_count': 21}, {'id': 1175, 'image_count': 91}, {'id': 1176, 'image_count': 31}, {'id': 1177, 'image_count': 1469}, {'id': 1178, 'image_count': 1924}, {'id': 1179, 'image_count': 87}, {'id': 1180, 'image_count': 77}, {'id': 1181, 'image_count': 11}, {'id': 1182, 'image_count': 47}, {'id': 1183, 'image_count': 21}, {'id': 1184, 'image_count': 47}, {'id': 1185, 'image_count': 70}, {'id': 1186, 'image_count': 1838}, {'id': 1187, 'image_count': 19}, {'id': 1188, 'image_count': 531}, {'id': 1189, 'image_count': 11}, {'id': 1190, 'image_count': 941}, {'id': 1191, 'image_count': 113}, {'id': 1192, 'image_count': 26}, {'id': 1193, 'image_count': 5}, {'id': 1194, 'image_count': 56}, {'id': 1195, 'image_count': 73}, {'id': 1196, 'image_count': 32}, {'id': 1197, 'image_count': 128}, {'id': 1198, 'image_count': 623}, {'id': 1199, 'image_count': 12}, {'id': 1200, 'image_count': 52}, {'id': 1201, 'image_count': 11}, {'id': 1202, 'image_count': 1674}, {'id': 1203, 'image_count': 81}]  # noqa
+# fmt: on

detectron2/data/datasets/pascal_voc.py

@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import numpy as np
+import os
+import xml.etree.ElementTree as ET
+from typing import List, Tuple, Union
+
+from detectron2.data import DatasetCatalog, MetadataCatalog
+from detectron2.structures import BoxMode
+from detectron2.utils.file_io import PathManager
+
+__all__ = ["load_voc_instances", "register_pascal_voc"]
+
+
+# fmt: off
+CLASS_NAMES = (
+    "aeroplane", "bicycle", "bird", "boat", "bottle", "bus", "car", "cat",
+    "chair", "cow", "diningtable", "dog", "horse", "motorbike", "person",
+    "pottedplant", "sheep", "sofa", "train", "tvmonitor"
+)
+# fmt: on
+
+
+def load_voc_instances(dirname: str, split: str, class_names: Union[List[str], Tuple[str, ...]]):
+    """
+    Load Pascal VOC detection annotations to Detectron2 format.
+
+    Args:
+        dirname: Contain "Annotations", "ImageSets", "JPEGImages"
+        split (str): one of "train", "test", "val", "trainval"
+        class_names: list or tuple of class names
+    """
+    with PathManager.open(os.path.join(dirname, "ImageSets", "Main", split + ".txt")) as f:
+        fileids = np.loadtxt(f, dtype=str)
+
+    # Needs to read many small annotation files. Makes sense at local
+    annotation_dirname = PathManager.get_local_path(os.path.join(dirname, "Annotations/"))
+    dicts = []
+    for fileid in fileids:
+        anno_file = os.path.join(annotation_dirname, fileid + ".xml")
+        jpeg_file = os.path.join(dirname, "JPEGImages", fileid + ".jpg")
+
+        with PathManager.open(anno_file) as f:
+            tree = ET.parse(f)
+
+        r = {
+            "file_name": jpeg_file,
+            "image_id": fileid,
+            "height": int(tree.findall("./size/height")[0].text),
+            "width": int(tree.findall("./size/width")[0].text),
+        }
+        instances = []
+
+        for obj in tree.findall("object"):
+            cls = obj.find("name").text
+            # We include "difficult" samples in training.
+            # Based on limited experiments, they don't hurt accuracy.
+            # difficult = int(obj.find("difficult").text)
+            # if difficult == 1:
+            # continue
+            bbox = obj.find("bndbox")
+            bbox = [float(bbox.find(x).text) for x in ["xmin", "ymin", "xmax", "ymax"]]
+            # Original annotations are integers in the range [1, W or H]
+            # Assuming they mean 1-based pixel indices (inclusive),
+            # a box with annotation (xmin=1, xmax=W) covers the whole image.
+            # In coordinate space this is represented by (xmin=0, xmax=W)
+            bbox[0] -= 1.0
+            bbox[1] -= 1.0
+            instances.append(
+                {"category_id": class_names.index(cls), "bbox": bbox, "bbox_mode": BoxMode.XYXY_ABS}
+            )
+        r["annotations"] = instances
+        dicts.append(r)
+    return dicts
+
+
+def register_pascal_voc(name, dirname, split, year, class_names=CLASS_NAMES):
+    DatasetCatalog.register(name, lambda: load_voc_instances(dirname, split, class_names))
+    MetadataCatalog.get(name).set(
+        thing_classes=list(class_names), dirname=dirname, year=year, split=split
+    )

detectron2/data/datasets/register_coco.py

@@ -0,0 +1,3 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .coco import register_coco_instances  # noqa
+from .coco_panoptic import register_coco_panoptic_separated  # noqa

detectron2/data/detection_utils.py

@@ -0,0 +1,661 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+"""
+Common data processing utilities that are used in a
+typical object detection data pipeline.
+"""
+import logging
+import numpy as np
+from typing import List, Union
+import pycocotools.mask as mask_util
+import torch
+from PIL import Image
+
+from detectron2.structures import (
+    BitMasks,
+    Boxes,
+    BoxMode,
+    Instances,
+    Keypoints,
+    PolygonMasks,
+    RotatedBoxes,
+    polygons_to_bitmask,
+)
+from detectron2.utils.file_io import PathManager
+
+from . import transforms as T
+from .catalog import MetadataCatalog
+
+__all__ = [
+    "SizeMismatchError",
+    "convert_image_to_rgb",
+    "check_image_size",
+    "transform_proposals",
+    "transform_instance_annotations",
+    "annotations_to_instances",
+    "annotations_to_instances_rotated",
+    "build_augmentation",
+    "build_transform_gen",
+    "create_keypoint_hflip_indices",
+    "filter_empty_instances",
+    "read_image",
+]
+
+
+class SizeMismatchError(ValueError):
+    """
+    When loaded image has difference width/height compared with annotation.
+    """
+
+
+# https://en.wikipedia.org/wiki/YUV#SDTV_with_BT.601
+_M_RGB2YUV = [[0.299, 0.587, 0.114], [-0.14713, -0.28886, 0.436], [0.615, -0.51499, -0.10001]]
+_M_YUV2RGB = [[1.0, 0.0, 1.13983], [1.0, -0.39465, -0.58060], [1.0, 2.03211, 0.0]]
+
+# https://www.exiv2.org/tags.html
+_EXIF_ORIENT = 274  # exif 'Orientation' tag
+
+
+def convert_PIL_to_numpy(image, format):
+    """
+    Convert PIL image to numpy array of target format.
+
+    Args:
+        image (PIL.Image): a PIL image
+        format (str): the format of output image
+
+    Returns:
+        (np.ndarray): also see `read_image`
+    """
+    if format is not None:
+        # PIL only supports RGB, so convert to RGB and flip channels over below
+        conversion_format = format
+        if format in ["BGR", "YUV-BT.601"]:
+            conversion_format = "RGB"
+        image = image.convert(conversion_format)
+    image = np.asarray(image)
+    # PIL squeezes out the channel dimension for "L", so make it HWC
+    if format == "L":
+        image = np.expand_dims(image, -1)
+
+    # handle formats not supported by PIL
+    elif format == "BGR":
+        # flip channels if needed
+        image = image[:, :, ::-1]
+    elif format == "YUV-BT.601":
+        image = image / 255.0
+        image = np.dot(image, np.array(_M_RGB2YUV).T)
+
+    return image
+
+
+def convert_image_to_rgb(image, format):
+    """
+    Convert an image from given format to RGB.
+
+    Args:
+        image (np.ndarray or Tensor): an HWC image
+        format (str): the format of input image, also see `read_image`
+
+    Returns:
+        (np.ndarray): (H,W,3) RGB image in 0-255 range, can be either float or uint8
+    """
+    if isinstance(image, torch.Tensor):
+        image = image.cpu().numpy()
+    if format == "BGR":
+        image = image[:, :, [2, 1, 0]]
+    elif format == "YUV-BT.601":
+        image = np.dot(image, np.array(_M_YUV2RGB).T)
+        image = image * 255.0
+    else:
+        if format == "L":
+            image = image[:, :, 0]
+        image = image.astype(np.uint8)
+        image = np.asarray(Image.fromarray(image, mode=format).convert("RGB"))
+    return image
+
+
+def _apply_exif_orientation(image):
+    """
+    Applies the exif orientation correctly.
+
+    This code exists per the bug:
+      https://github.com/python-pillow/Pillow/issues/3973
+    with the function `ImageOps.exif_transpose`. The Pillow source raises errors with
+    various methods, especially `tobytes`
+
+    Function based on:
+      https://github.com/wkentaro/labelme/blob/v4.5.4/labelme/utils/image.py#L59
+      https://github.com/python-pillow/Pillow/blob/7.1.2/src/PIL/ImageOps.py#L527
+
+    Args:
+        image (PIL.Image): a PIL image
+
+    Returns:
+        (PIL.Image): the PIL image with exif orientation applied, if applicable
+    """
+    if not hasattr(image, "getexif"):
+        return image
+
+    try:
+        exif = image.getexif()
+    except Exception:  # https://github.com/facebookresearch/detectron2/issues/1885
+        exif = None
+
+    if exif is None:
+        return image
+
+    orientation = exif.get(_EXIF_ORIENT)
+
+    method = {
+        2: Image.FLIP_LEFT_RIGHT,
+        3: Image.ROTATE_180,
+        4: Image.FLIP_TOP_BOTTOM,
+        5: Image.TRANSPOSE,
+        6: Image.ROTATE_270,
+        7: Image.TRANSVERSE,
+        8: Image.ROTATE_90,
+    }.get(orientation)
+
+    if method is not None:
+        return image.transpose(method)
+    return image
+
+
+def read_image(file_name, format=None):
+    """
+    Read an image into the given format.
+    Will apply rotation and flipping if the image has such exif information.
+
+    Args:
+        file_name (str): image file path
+        format (str): one of the supported image modes in PIL, or "BGR" or "YUV-BT.601".
+
+    Returns:
+        image (np.ndarray):
+            an HWC image in the given format, which is 0-255, uint8 for
+            supported image modes in PIL or "BGR"; float (0-1 for Y) for YUV-BT.601.
+    """
+    with PathManager.open(file_name, "rb") as f:
+        image = Image.open(f)
+
+        # work around this bug: https://github.com/python-pillow/Pillow/issues/3973
+        image = _apply_exif_orientation(image)
+        return convert_PIL_to_numpy(image, format)
+
+
+def check_image_size(dataset_dict, image):
+    """
+    Raise an error if the image does not match the size specified in the dict.
+    """
+    if "width" in dataset_dict or "height" in dataset_dict:
+        image_wh = (image.shape[1], image.shape[0])
+        expected_wh = (dataset_dict["width"], dataset_dict["height"])
+        if not image_wh == expected_wh:
+            raise SizeMismatchError(
+                "Mismatched image shape{}, got {}, expect {}.".format(
+                    (
+                        " for image " + dataset_dict["file_name"]
+                        if "file_name" in dataset_dict
+                        else ""
+                    ),
+                    image_wh,
+                    expected_wh,
+                )
+                + " Please check the width/height in your annotation."
+            )
+
+    # To ensure bbox always remap to original image size
+    if "width" not in dataset_dict:
+        dataset_dict["width"] = image.shape[1]
+    if "height" not in dataset_dict:
+        dataset_dict["height"] = image.shape[0]
+
+
+def transform_proposals(dataset_dict, image_shape, transforms, *, proposal_topk, min_box_size=0):
+    """
+    Apply transformations to the proposals in dataset_dict, if any.
+
+    Args:
+        dataset_dict (dict): a dict read from the dataset, possibly
+            contains fields "proposal_boxes", "proposal_objectness_logits", "proposal_bbox_mode"
+        image_shape (tuple): height, width
+        transforms (TransformList):
+        proposal_topk (int): only keep top-K scoring proposals
+        min_box_size (int): proposals with either side smaller than this
+            threshold are removed
+
+    The input dict is modified in-place, with abovementioned keys removed. A new
+    key "proposals" will be added. Its value is an `Instances`
+    object which contains the transformed proposals in its field
+    "proposal_boxes" and "objectness_logits".
+    """
+    if "proposal_boxes" in dataset_dict:
+        # Transform proposal boxes
+        boxes = transforms.apply_box(
+            BoxMode.convert(
+                dataset_dict.pop("proposal_boxes"),
+                dataset_dict.pop("proposal_bbox_mode"),
+                BoxMode.XYXY_ABS,
+            )
+        )
+        boxes = Boxes(boxes)
+        objectness_logits = torch.as_tensor(
+            dataset_dict.pop("proposal_objectness_logits").astype("float32")
+        )
+
+        boxes.clip(image_shape)
+        keep = boxes.nonempty(threshold=min_box_size)
+        boxes = boxes[keep]
+        objectness_logits = objectness_logits[keep]
+
+        proposals = Instances(image_shape)
+        proposals.proposal_boxes = boxes[:proposal_topk]
+        proposals.objectness_logits = objectness_logits[:proposal_topk]
+        dataset_dict["proposals"] = proposals
+
+
+def get_bbox(annotation):
+    """
+    Get bbox from data
+    Args:
+        annotation (dict): dict of instance annotations for a single instance.
+    Returns:
+        bbox (ndarray): x1, y1, x2, y2 coordinates
+    """
+    # bbox is 1d (per-instance bounding box)
+    bbox = BoxMode.convert(annotation["bbox"], annotation["bbox_mode"], BoxMode.XYXY_ABS)
+    return bbox
+
+
+def transform_instance_annotations(
+    annotation, transforms, image_size, *, keypoint_hflip_indices=None
+):
+    """
+    Apply transforms to box, segmentation and keypoints annotations of a single instance.
+
+    It will use `transforms.apply_box` for the box, and
+    `transforms.apply_coords` for segmentation polygons & keypoints.
+    If you need anything more specially designed for each data structure,
+    you'll need to implement your own version of this function or the transforms.
+
+    Args:
+        annotation (dict): dict of instance annotations for a single instance.
+            It will be modified in-place.
+        transforms (TransformList or list[Transform]):
+        image_size (tuple): the height, width of the transformed image
+        keypoint_hflip_indices (ndarray[int]): see `create_keypoint_hflip_indices`.
+
+    Returns:
+        dict:
+            the same input dict with fields "bbox", "segmentation", "keypoints"
+            transformed according to `transforms`.
+            The "bbox_mode" field will be set to XYXY_ABS.
+    """
+    if isinstance(transforms, (tuple, list)):
+        transforms = T.TransformList(transforms)
+    # bbox is 1d (per-instance bounding box)
+    bbox = BoxMode.convert(annotation["bbox"], annotation["bbox_mode"], BoxMode.XYXY_ABS)
+    # clip transformed bbox to image size
+    bbox = transforms.apply_box(np.array([bbox]))[0].clip(min=0)
+    annotation["bbox"] = np.minimum(bbox, list(image_size + image_size)[::-1])
+    annotation["bbox_mode"] = BoxMode.XYXY_ABS
+
+    if "segmentation" in annotation:
+        # each instance contains 1 or more polygons
+        segm = annotation["segmentation"]
+        if isinstance(segm, list):
+            # polygons
+            polygons = [np.asarray(p).reshape(-1, 2) for p in segm]
+            annotation["segmentation"] = [
+                p.reshape(-1) for p in transforms.apply_polygons(polygons)
+            ]
+        elif isinstance(segm, dict):
+            # RLE
+            mask = mask_util.decode(segm)
+            mask = transforms.apply_segmentation(mask)
+            assert tuple(mask.shape[:2]) == image_size
+            annotation["segmentation"] = mask
+        else:
+            raise ValueError(
+                "Cannot transform segmentation of type '{}'!"
+                "Supported types are: polygons as list[list[float] or ndarray],"
+                " COCO-style RLE as a dict.".format(type(segm))
+            )
+
+    if "keypoints" in annotation:
+        keypoints = transform_keypoint_annotations(
+            annotation["keypoints"], transforms, image_size, keypoint_hflip_indices
+        )
+        annotation["keypoints"] = keypoints
+
+    return annotation
+
+
+def transform_keypoint_annotations(keypoints, transforms, image_size, keypoint_hflip_indices=None):
+    """
+    Transform keypoint annotations of an image.
+    If a keypoint is transformed out of image boundary, it will be marked "unlabeled" (visibility=0)
+
+    Args:
+        keypoints (list[float]): Nx3 float in Detectron2's Dataset format.
+            Each point is represented by (x, y, visibility).
+        transforms (TransformList):
+        image_size (tuple): the height, width of the transformed image
+        keypoint_hflip_indices (ndarray[int]): see `create_keypoint_hflip_indices`.
+            When `transforms` includes horizontal flip, will use the index
+            mapping to flip keypoints.
+    """
+    # (N*3,) -> (N, 3)
+    keypoints = np.asarray(keypoints, dtype="float64").reshape(-1, 3)
+    keypoints_xy = transforms.apply_coords(keypoints[:, :2])
+
+    # Set all out-of-boundary points to "unlabeled"
+    inside = (keypoints_xy >= np.array([0, 0])) & (keypoints_xy <= np.array(image_size[::-1]))
+    inside = inside.all(axis=1)
+    keypoints[:, :2] = keypoints_xy
+    keypoints[:, 2][~inside] = 0
+
+    # This assumes that HorizFlipTransform is the only one that does flip
+    do_hflip = sum(isinstance(t, T.HFlipTransform) for t in transforms.transforms) % 2 == 1
+
+    # Alternative way: check if probe points was horizontally flipped.
+    # probe = np.asarray([[0.0, 0.0], [image_width, 0.0]])
+    # probe_aug = transforms.apply_coords(probe.copy())
+    # do_hflip = np.sign(probe[1][0] - probe[0][0]) != np.sign(probe_aug[1][0] - probe_aug[0][0])  # noqa
+
+    # If flipped, swap each keypoint with its opposite-handed equivalent
+    if do_hflip:
+        if keypoint_hflip_indices is None:
+            raise ValueError("Cannot flip keypoints without providing flip indices!")
+        if len(keypoints) != len(keypoint_hflip_indices):
+            raise ValueError(
+                "Keypoint data has {} points, but metadata "
+                "contains {} points!".format(len(keypoints), len(keypoint_hflip_indices))
+            )
+        keypoints = keypoints[np.asarray(keypoint_hflip_indices, dtype=np.int32), :]
+
+    # Maintain COCO convention that if visibility == 0 (unlabeled), then x, y = 0
+    keypoints[keypoints[:, 2] == 0] = 0
+    return keypoints
+
+
+def annotations_to_instances(annos, image_size, mask_format="polygon"):
+    """
+    Create an :class:`Instances` object used by the models,
+    from instance annotations in the dataset dict.
+
+    Args:
+        annos (list[dict]): a list of instance annotations in one image, each
+            element for one instance.
+        image_size (tuple): height, width
+
+    Returns:
+        Instances:
+            It will contain fields "gt_boxes", "gt_classes",
+            "gt_masks", "gt_keypoints", if they can be obtained from `annos`.
+            This is the format that builtin models expect.
+    """
+    boxes = (
+        np.stack(
+            [BoxMode.convert(obj["bbox"], obj["bbox_mode"], BoxMode.XYXY_ABS) for obj in annos]
+        )
+        if len(annos)
+        else np.zeros((0, 4))
+    )
+    target = Instances(image_size)
+    target.gt_boxes = Boxes(boxes)
+
+    classes = [int(obj["category_id"]) for obj in annos]
+    classes = torch.tensor(classes, dtype=torch.int64)
+    target.gt_classes = classes
+
+    if len(annos) and "segmentation" in annos[0]:
+        segms = [obj["segmentation"] for obj in annos]
+        if mask_format == "polygon":
+            try:
+                masks = PolygonMasks(segms)
+            except ValueError as e:
+                raise ValueError(
+                    "Failed to use mask_format=='polygon' from the given annotations!"
+                ) from e
+        else:
+            assert mask_format == "bitmask", mask_format
+            masks = []
+            for segm in segms:
+                if isinstance(segm, list):
+                    # polygon
+                    masks.append(polygons_to_bitmask(segm, *image_size))
+                elif isinstance(segm, dict):
+                    # COCO RLE
+                    masks.append(mask_util.decode(segm))
+                elif isinstance(segm, np.ndarray):
+                    assert segm.ndim == 2, "Expect segmentation of 2 dimensions, got {}.".format(
+                        segm.ndim
+                    )
+                    # mask array
+                    masks.append(segm)
+                else:
+                    raise ValueError(
+                        "Cannot convert segmentation of type '{}' to BitMasks!"
+                        "Supported types are: polygons as list[list[float] or ndarray],"
+                        " COCO-style RLE as a dict, or a binary segmentation mask "
+                        " in a 2D numpy array of shape HxW.".format(type(segm))
+                    )
+            # torch.from_numpy does not support array with negative stride.
+            masks = BitMasks(
+                torch.stack([torch.from_numpy(np.ascontiguousarray(x)) for x in masks])
+            )
+        target.gt_masks = masks
+
+    if len(annos) and "keypoints" in annos[0]:
+        kpts = [obj.get("keypoints", []) for obj in annos]
+        target.gt_keypoints = Keypoints(kpts)
+
+    return target
+
+
+def annotations_to_instances_rotated(annos, image_size):
+    """
+    Create an :class:`Instances` object used by the models,
+    from instance annotations in the dataset dict.
+    Compared to `annotations_to_instances`, this function is for rotated boxes only
+
+    Args:
+        annos (list[dict]): a list of instance annotations in one image, each
+            element for one instance.
+        image_size (tuple): height, width
+
+    Returns:
+        Instances:
+            Containing fields "gt_boxes", "gt_classes",
+            if they can be obtained from `annos`.
+            This is the format that builtin models expect.
+    """
+    boxes = [obj["bbox"] for obj in annos]
+    target = Instances(image_size)
+    boxes = target.gt_boxes = RotatedBoxes(boxes)
+    boxes.clip(image_size)
+
+    classes = [obj["category_id"] for obj in annos]
+    classes = torch.tensor(classes, dtype=torch.int64)
+    target.gt_classes = classes
+
+    return target
+
+
+def filter_empty_instances(
+    instances, by_box=True, by_mask=True, box_threshold=1e-5, return_mask=False
+):
+    """
+    Filter out empty instances in an `Instances` object.
+
+    Args:
+        instances (Instances):
+        by_box (bool): whether to filter out instances with empty boxes
+        by_mask (bool): whether to filter out instances with empty masks
+        box_threshold (float): minimum width and height to be considered non-empty
+        return_mask (bool): whether to return boolean mask of filtered instances
+
+    Returns:
+        Instances: the filtered instances.
+        tensor[bool], optional: boolean mask of filtered instances
+    """
+    assert by_box or by_mask
+    r = []
+    if by_box:
+        r.append(instances.gt_boxes.nonempty(threshold=box_threshold))
+    if instances.has("gt_masks") and by_mask:
+        r.append(instances.gt_masks.nonempty())
+
+    # TODO: can also filter visible keypoints
+
+    if not r:
+        return instances
+    m = r[0]
+    for x in r[1:]:
+        m = m & x
+    if return_mask:
+        return instances[m], m
+    return instances[m]
+
+
+def create_keypoint_hflip_indices(dataset_names: Union[str, List[str]]) -> List[int]:
+    """
+    Args:
+        dataset_names: list of dataset names
+
+    Returns:
+        list[int]: a list of size=#keypoints, storing the
+        horizontally-flipped keypoint indices.
+    """
+    if isinstance(dataset_names, str):
+        dataset_names = [dataset_names]
+
+    check_metadata_consistency("keypoint_names", dataset_names)
+    check_metadata_consistency("keypoint_flip_map", dataset_names)
+
+    meta = MetadataCatalog.get(dataset_names[0])
+    names = meta.keypoint_names
+    # TODO flip -> hflip
+    flip_map = dict(meta.keypoint_flip_map)
+    flip_map.update({v: k for k, v in flip_map.items()})
+    flipped_names = [i if i not in flip_map else flip_map[i] for i in names]
+    flip_indices = [names.index(i) for i in flipped_names]
+    return flip_indices
+
+
+def get_fed_loss_cls_weights(dataset_names: Union[str, List[str]], freq_weight_power=1.0):
+    """
+    Get frequency weight for each class sorted by class id.
+    We now calcualte freqency weight using image_count to the power freq_weight_power.
+
+    Args:
+        dataset_names: list of dataset names
+        freq_weight_power: power value
+    """
+    if isinstance(dataset_names, str):
+        dataset_names = [dataset_names]
+
+    check_metadata_consistency("class_image_count", dataset_names)
+
+    meta = MetadataCatalog.get(dataset_names[0])
+    class_freq_meta = meta.class_image_count
+    class_freq = torch.tensor(
+        [c["image_count"] for c in sorted(class_freq_meta, key=lambda x: x["id"])]
+    )
+    class_freq_weight = class_freq.float() ** freq_weight_power
+    return class_freq_weight
+
+
+def gen_crop_transform_with_instance(crop_size, image_size, instance):
+    """
+    Generate a CropTransform so that the cropping region contains
+    the center of the given instance.
+
+    Args:
+        crop_size (tuple): h, w in pixels
+        image_size (tuple): h, w
+        instance (dict): an annotation dict of one instance, in Detectron2's
+            dataset format.
+    """
+    crop_size = np.asarray(crop_size, dtype=np.int32)
+    bbox = BoxMode.convert(instance["bbox"], instance["bbox_mode"], BoxMode.XYXY_ABS)
+    center_yx = (bbox[1] + bbox[3]) * 0.5, (bbox[0] + bbox[2]) * 0.5
+    assert (
+        image_size[0] >= center_yx[0] and image_size[1] >= center_yx[1]
+    ), "The annotation bounding box is outside of the image!"
+    assert (
+        image_size[0] >= crop_size[0] and image_size[1] >= crop_size[1]
+    ), "Crop size is larger than image size!"
+
+    min_yx = np.maximum(np.floor(center_yx).astype(np.int32) - crop_size, 0)
+    max_yx = np.maximum(np.asarray(image_size, dtype=np.int32) - crop_size, 0)
+    max_yx = np.minimum(max_yx, np.ceil(center_yx).astype(np.int32))
+
+    y0 = np.random.randint(min_yx[0], max_yx[0] + 1)
+    x0 = np.random.randint(min_yx[1], max_yx[1] + 1)
+    return T.CropTransform(x0, y0, crop_size[1], crop_size[0])
+
+
+def check_metadata_consistency(key, dataset_names):
+    """
+    Check that the datasets have consistent metadata.
+
+    Args:
+        key (str): a metadata key
+        dataset_names (list[str]): a list of dataset names
+
+    Raises:
+        AttributeError: if the key does not exist in the metadata
+        ValueError: if the given datasets do not have the same metadata values defined by key
+    """
+    if len(dataset_names) == 0:
+        return
+    logger = logging.getLogger(__name__)
+    entries_per_dataset = [getattr(MetadataCatalog.get(d), key) for d in dataset_names]
+    for idx, entry in enumerate(entries_per_dataset):
+        if entry != entries_per_dataset[0]:
+            logger.error(
+                "Metadata '{}' for dataset '{}' is '{}'".format(key, dataset_names[idx], str(entry))
+            )
+            logger.error(
+                "Metadata '{}' for dataset '{}' is '{}'".format(
+                    key, dataset_names[0], str(entries_per_dataset[0])
+                )
+            )
+            raise ValueError("Datasets have different metadata '{}'!".format(key))
+
+
+def build_augmentation(cfg, is_train):
+    """
+    Create a list of default :class:`Augmentation` from config.
+    Now it includes resizing and flipping.
+
+    Returns:
+        list[Augmentation]
+    """
+    if is_train:
+        min_size = cfg.INPUT.MIN_SIZE_TRAIN
+        max_size = cfg.INPUT.MAX_SIZE_TRAIN
+        sample_style = cfg.INPUT.MIN_SIZE_TRAIN_SAMPLING
+    else:
+        min_size = cfg.INPUT.MIN_SIZE_TEST
+        max_size = cfg.INPUT.MAX_SIZE_TEST
+        sample_style = "choice"
+    augmentation = [T.ResizeShortestEdge(min_size, max_size, sample_style)]
+    if is_train and cfg.INPUT.RANDOM_FLIP != "none":
+        augmentation.append(
+            T.RandomFlip(
+                horizontal=cfg.INPUT.RANDOM_FLIP == "horizontal",
+                vertical=cfg.INPUT.RANDOM_FLIP == "vertical",
+            )
+        )
+    return augmentation
+
+
+build_transform_gen = build_augmentation
+"""
+Alias for backward-compatibility.
+"""

detectron2/data/samplers/__init__.py

@@ -0,0 +1,17 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .distributed_sampler import (
+    InferenceSampler,
+    RandomSubsetTrainingSampler,
+    RepeatFactorTrainingSampler,
+    TrainingSampler,
+)
+
+from .grouped_batch_sampler import GroupedBatchSampler
+
+__all__ = [
+    "GroupedBatchSampler",
+    "TrainingSampler",
+    "RandomSubsetTrainingSampler",
+    "InferenceSampler",
+    "RepeatFactorTrainingSampler",
+]

detectron2/data/samplers/distributed_sampler.py

@@ -0,0 +1,287 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import itertools
+import logging
+import math
+from collections import defaultdict
+from typing import Optional
+import torch
+from torch.utils.data.sampler import Sampler
+
+from detectron2.utils import comm
+
+logger = logging.getLogger(__name__)
+
+
+class TrainingSampler(Sampler):
+    """
+    In training, we only care about the "infinite stream" of training data.
+    So this sampler produces an infinite stream of indices and
+    all workers cooperate to correctly shuffle the indices and sample different indices.
+
+    The samplers in each worker effectively produces `indices[worker_id::num_workers]`
+    where `indices` is an infinite stream of indices consisting of
+    `shuffle(range(size)) + shuffle(range(size)) + ...` (if shuffle is True)
+    or `range(size) + range(size) + ...` (if shuffle is False)
+
+    Note that this sampler does not shard based on pytorch DataLoader worker id.
+    A sampler passed to pytorch DataLoader is used only with map-style dataset
+    and will not be executed inside workers.
+    But if this sampler is used in a way that it gets execute inside a dataloader
+    worker, then extra work needs to be done to shard its outputs based on worker id.
+    This is required so that workers don't produce identical data.
+    :class:`ToIterableDataset` implements this logic.
+    This note is true for all samplers in detectron2.
+    """
+
+    def __init__(self, size: int, shuffle: bool = True, seed: Optional[int] = None):
+        """
+        Args:
+            size (int): the total number of data of the underlying dataset to sample from
+            shuffle (bool): whether to shuffle the indices or not
+            seed (int): the initial seed of the shuffle. Must be the same
+                across all workers. If None, will use a random seed shared
+                among workers (require synchronization among all workers).
+        """
+        if not isinstance(size, int):
+            raise TypeError(f"TrainingSampler(size=) expects an int. Got type {type(size)}.")
+        if size <= 0:
+            raise ValueError(f"TrainingSampler(size=) expects a positive int. Got {size}.")
+        self._size = size
+        self._shuffle = shuffle
+        if seed is None:
+            seed = comm.shared_random_seed()
+        self._seed = int(seed)
+
+        self._rank = comm.get_rank()
+        self._world_size = comm.get_world_size()
+
+    def __iter__(self):
+        start = self._rank
+        yield from itertools.islice(self._infinite_indices(), start, None, self._world_size)
+
+    def _infinite_indices(self):
+        g = torch.Generator()
+        if self._seed is not None:
+            g.manual_seed(self._seed)
+        while True:
+            if self._shuffle:
+                yield from torch.randperm(self._size, generator=g).tolist()
+            else:
+                yield from torch.arange(self._size).tolist()
+
+
+class RandomSubsetTrainingSampler(TrainingSampler):
+    """
+    Similar to TrainingSampler, but only sample a random subset of indices.
+    This is useful when you want to estimate the accuracy vs data-number curves by
+      training the model with different subset_ratio.
+    """
+
+    def __init__(
+        self,
+        size: int,
+        subset_ratio: float,
+        shuffle: bool = True,
+        seed_shuffle: Optional[int] = None,
+        seed_subset: Optional[int] = None,
+    ):
+        """
+        Args:
+            size (int): the total number of data of the underlying dataset to sample from
+            subset_ratio (float): the ratio of subset data to sample from the underlying dataset
+            shuffle (bool): whether to shuffle the indices or not
+            seed_shuffle (int): the initial seed of the shuffle. Must be the same
+                across all workers. If None, will use a random seed shared
+                among workers (require synchronization among all workers).
+            seed_subset (int): the seed to randomize the subset to be sampled.
+                Must be the same across all workers. If None, will use a random seed shared
+                among workers (require synchronization among all workers).
+        """
+        super().__init__(size=size, shuffle=shuffle, seed=seed_shuffle)
+
+        assert 0.0 < subset_ratio <= 1.0
+        self._size_subset = int(size * subset_ratio)
+        assert self._size_subset > 0
+        if seed_subset is None:
+            seed_subset = comm.shared_random_seed()
+        self._seed_subset = int(seed_subset)
+
+        # randomly generate the subset indexes to be sampled from
+        g = torch.Generator()
+        g.manual_seed(self._seed_subset)
+        indexes_randperm = torch.randperm(self._size, generator=g)
+        self._indexes_subset = indexes_randperm[: self._size_subset]
+
+        logger.info("Using RandomSubsetTrainingSampler......")
+        logger.info(f"Randomly sample {self._size_subset} data from the original {self._size} data")
+
+    def _infinite_indices(self):
+        g = torch.Generator()
+        g.manual_seed(self._seed)  # self._seed equals seed_shuffle from __init__()
+        while True:
+            if self._shuffle:
+                # generate a random permutation to shuffle self._indexes_subset
+                randperm = torch.randperm(self._size_subset, generator=g)
+                yield from self._indexes_subset[randperm].tolist()
+            else:
+                yield from self._indexes_subset.tolist()
+
+
+class RepeatFactorTrainingSampler(Sampler):
+    """
+    Similar to TrainingSampler, but a sample may appear more times than others based
+    on its "repeat factor". This is suitable for training on class imbalanced datasets like LVIS.
+    """
+
+    def __init__(self, repeat_factors, *, shuffle=True, seed=None):
+        """
+        Args:
+            repeat_factors (Tensor): a float vector, the repeat factor for each indice. When it's
+                full of ones, it is equivalent to ``TrainingSampler(len(repeat_factors), ...)``.
+            shuffle (bool): whether to shuffle the indices or not
+            seed (int): the initial seed of the shuffle. Must be the same
+                across all workers. If None, will use a random seed shared
+                among workers (require synchronization among all workers).
+        """
+        self._shuffle = shuffle
+        if seed is None:
+            seed = comm.shared_random_seed()
+        self._seed = int(seed)
+
+        self._rank = comm.get_rank()
+        self._world_size = comm.get_world_size()
+
+        # Split into whole number (_int_part) and fractional (_frac_part) parts.
+        self._int_part = torch.trunc(repeat_factors)
+        self._frac_part = repeat_factors - self._int_part
+
+    @staticmethod
+    def repeat_factors_from_category_frequency(dataset_dicts, repeat_thresh, sqrt=True):
+        """
+        Compute (fractional) per-image repeat factors based on category frequency.
+        The repeat factor for an image is a function of the frequency of the rarest
+        category labeled in that image. The "frequency of category c" in [0, 1] is defined
+        as the fraction of images in the training set (without repeats) in which category c
+        appears.
+        See :paper:`lvis` (>= v2) Appendix B.2.
+
+        Args:
+            dataset_dicts (list[dict]): annotations in Detectron2 dataset format.
+            repeat_thresh (float): frequency threshold below which data is repeated.
+                If the frequency is half of `repeat_thresh`, the image will be
+                repeated twice.
+            sqrt (bool): if True, apply :func:`math.sqrt` to the repeat factor.
+
+        Returns:
+            torch.Tensor:
+                the i-th element is the repeat factor for the dataset image at index i.
+        """
+        # 1. For each category c, compute the fraction of images that contain it: f(c)
+        category_freq = defaultdict(int)
+        for dataset_dict in dataset_dicts:  # For each image (without repeats)
+            cat_ids = {ann["category_id"] for ann in dataset_dict["annotations"]}
+            for cat_id in cat_ids:
+                category_freq[cat_id] += 1
+        num_images = len(dataset_dicts)
+        for k, v in category_freq.items():
+            category_freq[k] = v / num_images
+
+        # 2. For each category c, compute the category-level repeat factor:
+        #    r(c) = max(1, sqrt(t / f(c)))
+        category_rep = {
+            cat_id: max(
+                1.0,
+                (math.sqrt(repeat_thresh / cat_freq) if sqrt else (repeat_thresh / cat_freq)),
+            )
+            for cat_id, cat_freq in category_freq.items()
+        }
+        for cat_id in sorted(category_rep.keys()):
+            logger.info(
+                f"Cat ID {cat_id}: freq={category_freq[cat_id]:.2f}, rep={category_rep[cat_id]:.2f}"
+            )
+
+        # 3. For each image I, compute the image-level repeat factor:
+        #    r(I) = max_{c in I} r(c)
+        rep_factors = []
+        for dataset_dict in dataset_dicts:
+            cat_ids = {ann["category_id"] for ann in dataset_dict["annotations"]}
+            rep_factor = max({category_rep[cat_id] for cat_id in cat_ids}, default=1.0)
+            rep_factors.append(rep_factor)
+
+        return torch.tensor(rep_factors, dtype=torch.float32)
+
+    def _get_epoch_indices(self, generator):
+        """
+        Create a list of dataset indices (with repeats) to use for one epoch.
+
+        Args:
+            generator (torch.Generator): pseudo random number generator used for
+                stochastic rounding.
+
+        Returns:
+            torch.Tensor: list of dataset indices to use in one epoch. Each index
+                is repeated based on its calculated repeat factor.
+        """
+        # Since repeat factors are fractional, we use stochastic rounding so
+        # that the target repeat factor is achieved in expectation over the
+        # course of training
+        rands = torch.rand(len(self._frac_part), generator=generator)
+        rep_factors = self._int_part + (rands < self._frac_part).float()
+        # Construct a list of indices in which we repeat images as specified
+        indices = []
+        for dataset_index, rep_factor in enumerate(rep_factors):
+            indices.extend([dataset_index] * int(rep_factor.item()))
+        return torch.tensor(indices, dtype=torch.int64)
+
+    def __iter__(self):
+        start = self._rank
+        yield from itertools.islice(self._infinite_indices(), start, None, self._world_size)
+
+    def _infinite_indices(self):
+        g = torch.Generator()
+        g.manual_seed(self._seed)
+        while True:
+            # Sample indices with repeats determined by stochastic rounding; each
+            # "epoch" may have a slightly different size due to the rounding.
+            indices = self._get_epoch_indices(g)
+            if self._shuffle:
+                randperm = torch.randperm(len(indices), generator=g)
+                yield from indices[randperm].tolist()
+            else:
+                yield from indices.tolist()
+
+
+class InferenceSampler(Sampler):
+    """
+    Produce indices for inference across all workers.
+    Inference needs to run on the __exact__ set of samples,
+    therefore when the total number of samples is not divisible by the number of workers,
+    this sampler produces different number of samples on different workers.
+    """
+
+    def __init__(self, size: int):
+        """
+        Args:
+            size (int): the total number of data of the underlying dataset to sample from
+        """
+        self._size = size
+        assert size > 0
+        self._rank = comm.get_rank()
+        self._world_size = comm.get_world_size()
+        self._local_indices = self._get_local_indices(size, self._world_size, self._rank)
+
+    @staticmethod
+    def _get_local_indices(total_size, world_size, rank):
+        shard_size = total_size // world_size
+        left = total_size % world_size
+        shard_sizes = [shard_size + int(r < left) for r in range(world_size)]
+
+        begin = sum(shard_sizes[:rank])
+        end = min(sum(shard_sizes[: rank + 1]), total_size)
+        return range(begin, end)
+
+    def __iter__(self):
+        yield from self._local_indices
+
+    def __len__(self):
+        return len(self._local_indices)

detectron2/data/samplers/grouped_batch_sampler.py

@@ -0,0 +1,47 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import numpy as np
+from torch.utils.data.sampler import BatchSampler, Sampler
+
+
+class GroupedBatchSampler(BatchSampler):
+    """
+    Wraps another sampler to yield a mini-batch of indices.
+    It enforces that the batch only contain elements from the same group.
+    It also tries to provide mini-batches which follows an ordering which is
+    as close as possible to the ordering from the original sampler.
+    """
+
+    def __init__(self, sampler, group_ids, batch_size):
+        """
+        Args:
+            sampler (Sampler): Base sampler.
+            group_ids (list[int]): If the sampler produces indices in range [0, N),
+                `group_ids` must be a list of `N` ints which contains the group id of each sample.
+                The group ids must be a set of integers in the range [0, num_groups).
+            batch_size (int): Size of mini-batch.
+        """
+        if not isinstance(sampler, Sampler):
+            raise ValueError(
+                "sampler should be an instance of "
+                "torch.utils.data.Sampler, but got sampler={}".format(sampler)
+            )
+        self.sampler = sampler
+        self.group_ids = np.asarray(group_ids)
+        assert self.group_ids.ndim == 1
+        self.batch_size = batch_size
+        groups = np.unique(self.group_ids).tolist()
+
+        # buffer the indices of each group until batch size is reached
+        self.buffer_per_group = {k: [] for k in groups}
+
+    def __iter__(self):
+        for idx in self.sampler:
+            group_id = self.group_ids[idx]
+            group_buffer = self.buffer_per_group[group_id]
+            group_buffer.append(idx)
+            if len(group_buffer) == self.batch_size:
+                yield group_buffer[:]  # yield a copy of the list
+                del group_buffer[:]
+
+    def __len__(self):
+        raise NotImplementedError("len() of GroupedBatchSampler is not well-defined.")

detectron2/data/transforms/__init__.py

@@ -0,0 +1,14 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from fvcore.transforms.transform import Transform, TransformList  # order them first
+from fvcore.transforms.transform import *
+from .transform import *
+from .augmentation import *
+from .augmentation_impl import *
+
+__all__ = [k for k in globals().keys() if not k.startswith("_")]
+
+
+from detectron2.utils.env import fixup_module_metadata
+
+fixup_module_metadata(__name__, globals(), __all__)
+del fixup_module_metadata

detectron2/data/transforms/augmentation.py

@@ -0,0 +1,380 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import inspect
+import numpy as np
+import pprint
+from typing import Any, List, Optional, Tuple, Union
+from fvcore.transforms.transform import Transform, TransformList
+
+"""
+See "Data Augmentation" tutorial for an overview of the system:
+https://detectron2.readthedocs.io/tutorials/augmentation.html
+"""
+
+
+__all__ = [
+    "Augmentation",
+    "AugmentationList",
+    "AugInput",
+    "TransformGen",
+    "apply_transform_gens",
+    "StandardAugInput",
+    "apply_augmentations",
+]
+
+
+def _check_img_dtype(img):
+    assert isinstance(img, np.ndarray), "[Augmentation] Needs an numpy array, but got a {}!".format(
+        type(img)
+    )
+    assert not isinstance(img.dtype, np.integer) or (
+        img.dtype == np.uint8
+    ), "[Augmentation] Got image of type {}, use uint8 or floating points instead!".format(
+        img.dtype
+    )
+    assert img.ndim in [2, 3], img.ndim
+
+
+def _get_aug_input_args(aug, aug_input) -> List[Any]:
+    """
+    Get the arguments to be passed to ``aug.get_transform`` from the input ``aug_input``.
+    """
+    if aug.input_args is None:
+        # Decide what attributes are needed automatically
+        prms = list(inspect.signature(aug.get_transform).parameters.items())
+        # The default behavior is: if there is one parameter, then its "image"
+        # (work automatically for majority of use cases, and also avoid BC breaking),
+        # Otherwise, use the argument names.
+        if len(prms) == 1:
+            names = ("image",)
+        else:
+            names = []
+            for name, prm in prms:
+                if prm.kind in (
+                    inspect.Parameter.VAR_POSITIONAL,
+                    inspect.Parameter.VAR_KEYWORD,
+                ):
+                    raise TypeError(
+                        f""" \
+The default implementation of `{type(aug)}.__call__` does not allow \
+`{type(aug)}.get_transform` to use variable-length arguments (*args, **kwargs)! \
+If arguments are unknown, reimplement `__call__` instead. \
+"""
+                    )
+                names.append(name)
+        aug.input_args = tuple(names)
+
+    args = []
+    for f in aug.input_args:
+        try:
+            args.append(getattr(aug_input, f))
+        except AttributeError as e:
+            raise AttributeError(
+                f"{type(aug)}.get_transform needs input attribute '{f}', "
+                f"but it is not an attribute of {type(aug_input)}!"
+            ) from e
+    return args
+
+
+class Augmentation:
+    """
+    Augmentation defines (often random) policies/strategies to generate :class:`Transform`
+    from data. It is often used for pre-processing of input data.
+
+    A "policy" that generates a :class:`Transform` may, in the most general case,
+    need arbitrary information from input data in order to determine what transforms
+    to apply. Therefore, each :class:`Augmentation` instance defines the arguments
+    needed by its :meth:`get_transform` method. When called with the positional arguments,
+    the :meth:`get_transform` method executes the policy.
+
+    Note that :class:`Augmentation` defines the policies to create a :class:`Transform`,
+    but not how to execute the actual transform operations to those data.
+    Its :meth:`__call__` method will use :meth:`AugInput.transform` to execute the transform.
+
+    The returned `Transform` object is meant to describe deterministic transformation, which means
+    it can be re-applied on associated data, e.g. the geometry of an image and its segmentation
+    masks need to be transformed together.
+    (If such re-application is not needed, then determinism is not a crucial requirement.)
+    """
+
+    input_args: Optional[Tuple[str]] = None
+    """
+    Stores the attribute names needed by :meth:`get_transform`, e.g.  ``("image", "sem_seg")``.
+    By default, it is just a tuple of argument names in :meth:`self.get_transform`, which often only
+    contain "image". As long as the argument name convention is followed, there is no need for
+    users to touch this attribute.
+    """
+
+    def _init(self, params=None):
+        if params:
+            for k, v in params.items():
+                if k != "self" and not k.startswith("_"):
+                    setattr(self, k, v)
+
+    def get_transform(self, *args) -> Transform:
+        """
+        Execute the policy based on input data, and decide what transform to apply to inputs.
+
+        Args:
+            args: Any fixed-length positional arguments. By default, the name of the arguments
+                should exist in the :class:`AugInput` to be used.
+
+        Returns:
+            Transform: Returns the deterministic transform to apply to the input.
+
+        Examples:
+        ::
+            class MyAug:
+                # if a policy needs to know both image and semantic segmentation
+                def get_transform(image, sem_seg) -> T.Transform:
+                    pass
+            tfm: Transform = MyAug().get_transform(image, sem_seg)
+            new_image = tfm.apply_image(image)
+
+        Notes:
+            Users can freely use arbitrary new argument names in custom
+            :meth:`get_transform` method, as long as they are available in the
+            input data. In detectron2 we use the following convention:
+
+            * image: (H,W) or (H,W,C) ndarray of type uint8 in range [0, 255], or
+              floating point in range [0, 1] or [0, 255].
+            * boxes: (N,4) ndarray of float32. It represents the instance bounding boxes
+              of N instances. Each is in XYXY format in unit of absolute coordinates.
+            * sem_seg: (H,W) ndarray of type uint8. Each element is an integer label of pixel.
+
+            We do not specify convention for other types and do not include builtin
+            :class:`Augmentation` that uses other types in detectron2.
+        """
+        raise NotImplementedError
+
+    def __call__(self, aug_input) -> Transform:
+        """
+        Augment the given `aug_input` **in-place**, and return the transform that's used.
+
+        This method will be called to apply the augmentation. In most augmentation, it
+        is enough to use the default implementation, which calls :meth:`get_transform`
+        using the inputs. But a subclass can overwrite it to have more complicated logic.
+
+        Args:
+            aug_input (AugInput): an object that has attributes needed by this augmentation
+                (defined by ``self.get_transform``). Its ``transform`` method will be called
+                to in-place transform it.
+
+        Returns:
+            Transform: the transform that is applied on the input.
+        """
+        args = _get_aug_input_args(self, aug_input)
+        tfm = self.get_transform(*args)
+        assert isinstance(tfm, (Transform, TransformList)), (
+            f"{type(self)}.get_transform must return an instance of Transform! "
+            f"Got {type(tfm)} instead."
+        )
+        aug_input.transform(tfm)
+        return tfm
+
+    def _rand_range(self, low=1.0, high=None, size=None):
+        """
+        Uniform float random number between low and high.
+        """
+        if high is None:
+            low, high = 0, low
+        if size is None:
+            size = []
+        return np.random.uniform(low, high, size)
+
+    def __repr__(self):
+        """
+        Produce something like:
+        "MyAugmentation(field1={self.field1}, field2={self.field2})"
+        """
+        try:
+            sig = inspect.signature(self.__init__)
+            classname = type(self).__name__
+            argstr = []
+            for name, param in sig.parameters.items():
+                assert (
+                    param.kind != param.VAR_POSITIONAL and param.kind != param.VAR_KEYWORD
+                ), "The default __repr__ doesn't support *args or **kwargs"
+                assert hasattr(self, name), (
+                    "Attribute {} not found! "
+                    "Default __repr__ only works if attributes match the constructor.".format(name)
+                )
+                attr = getattr(self, name)
+                default = param.default
+                if default is attr:
+                    continue
+                attr_str = pprint.pformat(attr)
+                if "\n" in attr_str:
+                    # don't show it if pformat decides to use >1 lines
+                    attr_str = "..."
+                argstr.append("{}={}".format(name, attr_str))
+            return "{}({})".format(classname, ", ".join(argstr))
+        except AssertionError:
+            return super().__repr__()
+
+    __str__ = __repr__
+
+
+class _TransformToAug(Augmentation):
+    def __init__(self, tfm: Transform):
+        self.tfm = tfm
+
+    def get_transform(self, *args):
+        return self.tfm
+
+    def __repr__(self):
+        return repr(self.tfm)
+
+    __str__ = __repr__
+
+
+def _transform_to_aug(tfm_or_aug):
+    """
+    Wrap Transform into Augmentation.
+    Private, used internally to implement augmentations.
+    """
+    assert isinstance(tfm_or_aug, (Transform, Augmentation)), tfm_or_aug
+    if isinstance(tfm_or_aug, Augmentation):
+        return tfm_or_aug
+    else:
+        return _TransformToAug(tfm_or_aug)
+
+
+class AugmentationList(Augmentation):
+    """
+    Apply a sequence of augmentations.
+
+    It has ``__call__`` method to apply the augmentations.
+
+    Note that :meth:`get_transform` method is impossible (will throw error if called)
+    for :class:`AugmentationList`, because in order to apply a sequence of augmentations,
+    the kth augmentation must be applied first, to provide inputs needed by the (k+1)th
+    augmentation.
+    """
+
+    def __init__(self, augs):
+        """
+        Args:
+            augs (list[Augmentation or Transform]):
+        """
+        super().__init__()
+        self.augs = [_transform_to_aug(x) for x in augs]
+
+    def __call__(self, aug_input) -> TransformList:
+        tfms = []
+        for x in self.augs:
+            tfm = x(aug_input)
+            tfms.append(tfm)
+        return TransformList(tfms)
+
+    def __repr__(self):
+        msgs = [str(x) for x in self.augs]
+        return "AugmentationList[{}]".format(", ".join(msgs))
+
+    __str__ = __repr__
+
+
+class AugInput:
+    """
+    Input that can be used with :meth:`Augmentation.__call__`.
+    This is a standard implementation for the majority of use cases.
+    This class provides the standard attributes **"image", "boxes", "sem_seg"**
+    defined in :meth:`__init__` and they may be needed by different augmentations.
+    Most augmentation policies do not need attributes beyond these three.
+
+    After applying augmentations to these attributes (using :meth:`AugInput.transform`),
+    the returned transforms can then be used to transform other data structures that users have.
+
+    Examples:
+    ::
+        input = AugInput(image, boxes=boxes)
+        tfms = augmentation(input)
+        transformed_image = input.image
+        transformed_boxes = input.boxes
+        transformed_other_data = tfms.apply_other(other_data)
+
+    An extended project that works with new data types may implement augmentation policies
+    that need other inputs. An algorithm may need to transform inputs in a way different
+    from the standard approach defined in this class. In those rare situations, users can
+    implement a class similar to this class, that satify the following condition:
+
+    * The input must provide access to these data in the form of attribute access
+      (``getattr``).  For example, if an :class:`Augmentation` to be applied needs "image"
+      and "sem_seg" arguments, its input must have the attribute "image" and "sem_seg".
+    * The input must have a ``transform(tfm: Transform) -> None`` method which
+      in-place transforms all its attributes.
+    """
+
+    # TODO maybe should support more builtin data types here
+    def __init__(
+        self,
+        image: np.ndarray,
+        *,
+        boxes: Optional[np.ndarray] = None,
+        sem_seg: Optional[np.ndarray] = None,
+    ):
+        """
+        Args:
+            image (ndarray): (H,W) or (H,W,C) ndarray of type uint8 in range [0, 255], or
+                floating point in range [0, 1] or [0, 255]. The meaning of C is up
+                to users.
+            boxes (ndarray or None): Nx4 float32 boxes in XYXY_ABS mode
+            sem_seg (ndarray or None): HxW uint8 semantic segmentation mask. Each element
+                is an integer label of pixel.
+        """
+        _check_img_dtype(image)
+        self.image = image
+        self.boxes = boxes
+        self.sem_seg = sem_seg
+
+    def transform(self, tfm: Transform) -> None:
+        """
+        In-place transform all attributes of this class.
+
+        By "in-place", it means after calling this method, accessing an attribute such
+        as ``self.image`` will return transformed data.
+        """
+        self.image = tfm.apply_image(self.image)
+        if self.boxes is not None:
+            self.boxes = tfm.apply_box(self.boxes)
+        if self.sem_seg is not None:
+            self.sem_seg = tfm.apply_segmentation(self.sem_seg)
+
+    def apply_augmentations(
+        self, augmentations: List[Union[Augmentation, Transform]]
+    ) -> TransformList:
+        """
+        Equivalent of ``AugmentationList(augmentations)(self)``
+        """
+        return AugmentationList(augmentations)(self)
+
+
+def apply_augmentations(augmentations: List[Union[Transform, Augmentation]], inputs):
+    """
+    Use ``T.AugmentationList(augmentations)(inputs)`` instead.
+    """
+    if isinstance(inputs, np.ndarray):
+        # handle the common case of image-only Augmentation, also for backward compatibility
+        image_only = True
+        inputs = AugInput(inputs)
+    else:
+        image_only = False
+    tfms = inputs.apply_augmentations(augmentations)
+    return inputs.image if image_only else inputs, tfms
+
+
+apply_transform_gens = apply_augmentations
+"""
+Alias for backward-compatibility.
+"""
+
+TransformGen = Augmentation
+"""
+Alias for Augmentation, since it is something that generates :class:`Transform`s
+"""
+
+StandardAugInput = AugInput
+"""
+Alias for compatibility. It's not worth the complexity to have two classes.
+"""

detectron2/data/transforms/augmentation_impl.py

@@ -0,0 +1,736 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+"""
+Implement many useful :class:`Augmentation`.
+"""
+import numpy as np
+import sys
+from numpy import random
+from typing import Tuple
+import torch
+from fvcore.transforms.transform import (
+    BlendTransform,
+    CropTransform,
+    HFlipTransform,
+    NoOpTransform,
+    PadTransform,
+    Transform,
+    TransformList,
+    VFlipTransform,
+)
+from PIL import Image
+
+from detectron2.structures import Boxes, pairwise_iou
+
+from .augmentation import Augmentation, _transform_to_aug
+from .transform import ExtentTransform, ResizeTransform, RotationTransform
+
+__all__ = [
+    "FixedSizeCrop",
+    "RandomApply",
+    "RandomBrightness",
+    "RandomContrast",
+    "RandomCrop",
+    "RandomExtent",
+    "RandomFlip",
+    "RandomSaturation",
+    "RandomLighting",
+    "RandomRotation",
+    "Resize",
+    "ResizeScale",
+    "ResizeShortestEdge",
+    "RandomCrop_CategoryAreaConstraint",
+    "RandomResize",
+    "MinIoURandomCrop",
+]
+
+
+class RandomApply(Augmentation):
+    """
+    Randomly apply an augmentation with a given probability.
+    """
+
+    def __init__(self, tfm_or_aug, prob=0.5):
+        """
+        Args:
+            tfm_or_aug (Transform, Augmentation): the transform or augmentation
+                to be applied. It can either be a `Transform` or `Augmentation`
+                instance.
+            prob (float): probability between 0.0 and 1.0 that
+                the wrapper transformation is applied
+        """
+        super().__init__()
+        self.aug = _transform_to_aug(tfm_or_aug)
+        assert 0.0 <= prob <= 1.0, f"Probablity must be between 0.0 and 1.0 (given: {prob})"
+        self.prob = prob
+
+    def get_transform(self, *args):
+        do = self._rand_range() < self.prob
+        if do:
+            return self.aug.get_transform(*args)
+        else:
+            return NoOpTransform()
+
+    def __call__(self, aug_input):
+        do = self._rand_range() < self.prob
+        if do:
+            return self.aug(aug_input)
+        else:
+            return NoOpTransform()
+
+
+class RandomFlip(Augmentation):
+    """
+    Flip the image horizontally or vertically with the given probability.
+    """
+
+    def __init__(self, prob=0.5, *, horizontal=True, vertical=False):
+        """
+        Args:
+            prob (float): probability of flip.
+            horizontal (boolean): whether to apply horizontal flipping
+            vertical (boolean): whether to apply vertical flipping
+        """
+        super().__init__()
+
+        if horizontal and vertical:
+            raise ValueError("Cannot do both horiz and vert. Please use two Flip instead.")
+        if not horizontal and not vertical:
+            raise ValueError("At least one of horiz or vert has to be True!")
+        self._init(locals())
+
+    def get_transform(self, image):
+        h, w = image.shape[:2]
+        do = self._rand_range() < self.prob
+        if do:
+            if self.horizontal:
+                return HFlipTransform(w)
+            elif self.vertical:
+                return VFlipTransform(h)
+        else:
+            return NoOpTransform()
+
+
+class Resize(Augmentation):
+    """Resize image to a fixed target size"""
+
+    def __init__(self, shape, interp=Image.BILINEAR):
+        """
+        Args:
+            shape: (h, w) tuple or a int
+            interp: PIL interpolation method
+        """
+        if isinstance(shape, int):
+            shape = (shape, shape)
+        shape = tuple(shape)
+        self._init(locals())
+
+    def get_transform(self, image):
+        return ResizeTransform(
+            image.shape[0], image.shape[1], self.shape[0], self.shape[1], self.interp
+        )
+
+
+class ResizeShortestEdge(Augmentation):
+    """
+    Resize the image while keeping the aspect ratio unchanged.
+    It attempts to scale the shorter edge to the given `short_edge_length`,
+    as long as the longer edge does not exceed `max_size`.
+    If `max_size` is reached, then downscale so that the longer edge does not exceed max_size.
+    """
+
+    @torch.jit.unused
+    def __init__(
+        self, short_edge_length, max_size=sys.maxsize, sample_style="range", interp=Image.BILINEAR
+    ):
+        """
+        Args:
+            short_edge_length (list[int]): If ``sample_style=="range"``,
+                a [min, max] interval from which to sample the shortest edge length.
+                If ``sample_style=="choice"``, a list of shortest edge lengths to sample from.
+            max_size (int): maximum allowed longest edge length.
+            sample_style (str): either "range" or "choice".
+        """
+        super().__init__()
+        assert sample_style in ["range", "choice"], sample_style
+
+        self.is_range = sample_style == "range"
+        if isinstance(short_edge_length, int):
+            short_edge_length = (short_edge_length, short_edge_length)
+        if self.is_range:
+            assert len(short_edge_length) == 2, (
+                "short_edge_length must be two values using 'range' sample style."
+                f" Got {short_edge_length}!"
+            )
+        self._init(locals())
+
+    @torch.jit.unused
+    def get_transform(self, image):
+        h, w = image.shape[:2]
+        if self.is_range:
+            size = np.random.randint(self.short_edge_length[0], self.short_edge_length[1] + 1)
+        else:
+            size = np.random.choice(self.short_edge_length)
+        if size == 0:
+            return NoOpTransform()
+
+        newh, neww = ResizeShortestEdge.get_output_shape(h, w, size, self.max_size)
+        return ResizeTransform(h, w, newh, neww, self.interp)
+
+    @staticmethod
+    def get_output_shape(
+        oldh: int, oldw: int, short_edge_length: int, max_size: int
+    ) -> Tuple[int, int]:
+        """
+        Compute the output size given input size and target short edge length.
+        """
+        h, w = oldh, oldw
+        size = short_edge_length * 1.0
+        scale = size / min(h, w)
+        if h < w:
+            newh, neww = size, scale * w
+        else:
+            newh, neww = scale * h, size
+        if max(newh, neww) > max_size:
+            scale = max_size * 1.0 / max(newh, neww)
+            newh = newh * scale
+            neww = neww * scale
+        neww = int(neww + 0.5)
+        newh = int(newh + 0.5)
+        return (newh, neww)
+
+
+class ResizeScale(Augmentation):
+    """
+    Takes target size as input and randomly scales the given target size between `min_scale`
+    and `max_scale`. It then scales the input image such that it fits inside the scaled target
+    box, keeping the aspect ratio constant.
+    This implements the resize part of the Google's 'resize_and_crop' data augmentation:
+    https://github.com/tensorflow/tpu/blob/master/models/official/detection/utils/input_utils.py#L127
+    """
+
+    def __init__(
+        self,
+        min_scale: float,
+        max_scale: float,
+        target_height: int,
+        target_width: int,
+        interp: int = Image.BILINEAR,
+    ):
+        """
+        Args:
+            min_scale: minimum image scale range.
+            max_scale: maximum image scale range.
+            target_height: target image height.
+            target_width: target image width.
+            interp: image interpolation method.
+        """
+        super().__init__()
+        self._init(locals())
+
+    def _get_resize(self, image: np.ndarray, scale: float) -> Transform:
+        input_size = image.shape[:2]
+
+        # Compute new target size given a scale.
+        target_size = (self.target_height, self.target_width)
+        target_scale_size = np.multiply(target_size, scale)
+
+        # Compute actual rescaling applied to input image and output size.
+        output_scale = np.minimum(
+            target_scale_size[0] / input_size[0], target_scale_size[1] / input_size[1]
+        )
+        output_size = np.round(np.multiply(input_size, output_scale)).astype(int)
+
+        return ResizeTransform(
+            input_size[0], input_size[1], int(output_size[0]), int(output_size[1]), self.interp
+        )
+
+    def get_transform(self, image: np.ndarray) -> Transform:
+        random_scale = np.random.uniform(self.min_scale, self.max_scale)
+        return self._get_resize(image, random_scale)
+
+
+class RandomRotation(Augmentation):
+    """
+    This method returns a copy of this image, rotated the given
+    number of degrees counter clockwise around the given center.
+    """
+
+    def __init__(self, angle, expand=True, center=None, sample_style="range", interp=None):
+        """
+        Args:
+            angle (list[float]): If ``sample_style=="range"``,
+                a [min, max] interval from which to sample the angle (in degrees).
+                If ``sample_style=="choice"``, a list of angles to sample from
+            expand (bool): choose if the image should be resized to fit the whole
+                rotated image (default), or simply cropped
+            center (list[[float, float]]):  If ``sample_style=="range"``,
+                a [[minx, miny], [maxx, maxy]] relative interval from which to sample the center,
+                [0, 0] being the top left of the image and [1, 1] the bottom right.
+                If ``sample_style=="choice"``, a list of centers to sample from
+                Default: None, which means that the center of rotation is the center of the image
+                center has no effect if expand=True because it only affects shifting
+        """
+        super().__init__()
+        assert sample_style in ["range", "choice"], sample_style
+        self.is_range = sample_style == "range"
+        if isinstance(angle, (float, int)):
+            angle = (angle, angle)
+        if center is not None and isinstance(center[0], (float, int)):
+            center = (center, center)
+        self._init(locals())
+
+    def get_transform(self, image):
+        h, w = image.shape[:2]
+        center = None
+        if self.is_range:
+            angle = np.random.uniform(self.angle[0], self.angle[1])
+            if self.center is not None:
+                center = (
+                    np.random.uniform(self.center[0][0], self.center[1][0]),
+                    np.random.uniform(self.center[0][1], self.center[1][1]),
+                )
+        else:
+            angle = np.random.choice(self.angle)
+            if self.center is not None:
+                center = np.random.choice(self.center)
+
+        if center is not None:
+            center = (w * center[0], h * center[1])  # Convert to absolute coordinates
+
+        if angle % 360 == 0:
+            return NoOpTransform()
+
+        return RotationTransform(h, w, angle, expand=self.expand, center=center, interp=self.interp)
+
+
+class FixedSizeCrop(Augmentation):
+    """
+    If `crop_size` is smaller than the input image size, then it uses a random crop of
+    the crop size. If `crop_size` is larger than the input image size, then it pads
+    the right and the bottom of the image to the crop size if `pad` is True, otherwise
+    it returns the smaller image.
+    """
+
+    def __init__(
+        self,
+        crop_size: Tuple[int],
+        pad: bool = True,
+        pad_value: float = 128.0,
+        seg_pad_value: int = 255,
+    ):
+        """
+        Args:
+            crop_size: target image (height, width).
+            pad: if True, will pad images smaller than `crop_size` up to `crop_size`
+            pad_value: the padding value to the image.
+            seg_pad_value: the padding value to the segmentation mask.
+        """
+        super().__init__()
+        self._init(locals())
+
+    def _get_crop(self, image: np.ndarray) -> Transform:
+        # Compute the image scale and scaled size.
+        input_size = image.shape[:2]
+        output_size = self.crop_size
+
+        # Add random crop if the image is scaled up.
+        max_offset = np.subtract(input_size, output_size)
+        max_offset = np.maximum(max_offset, 0)
+        offset = np.multiply(max_offset, np.random.uniform(0.0, 1.0))
+        offset = np.round(offset).astype(int)
+        return CropTransform(
+            offset[1], offset[0], output_size[1], output_size[0], input_size[1], input_size[0]
+        )
+
+    def _get_pad(self, image: np.ndarray) -> Transform:
+        # Compute the image scale and scaled size.
+        input_size = image.shape[:2]
+        output_size = self.crop_size
+
+        # Add padding if the image is scaled down.
+        pad_size = np.subtract(output_size, input_size)
+        pad_size = np.maximum(pad_size, 0)
+        original_size = np.minimum(input_size, output_size)
+        return PadTransform(
+            0,
+            0,
+            pad_size[1],
+            pad_size[0],
+            original_size[1],
+            original_size[0],
+            self.pad_value,
+            self.seg_pad_value,
+        )
+
+    def get_transform(self, image: np.ndarray) -> TransformList:
+        transforms = [self._get_crop(image)]
+        if self.pad:
+            transforms.append(self._get_pad(image))
+        return TransformList(transforms)
+
+
+class RandomCrop(Augmentation):
+    """
+    Randomly crop a rectangle region out of an image.
+    """
+
+    def __init__(self, crop_type: str, crop_size):
+        """
+        Args:
+            crop_type (str): one of "relative_range", "relative", "absolute", "absolute_range".
+            crop_size (tuple[float, float]): two floats, explained below.
+
+        - "relative": crop a (H * crop_size[0], W * crop_size[1]) region from an input image of
+          size (H, W). crop size should be in (0, 1]
+        - "relative_range": uniformly sample two values from [crop_size[0], 1]
+          and [crop_size[1]], 1], and use them as in "relative" crop type.
+        - "absolute" crop a (crop_size[0], crop_size[1]) region from input image.
+          crop_size must be smaller than the input image size.
+        - "absolute_range", for an input of size (H, W), uniformly sample H_crop in
+          [crop_size[0], min(H, crop_size[1])] and W_crop in [crop_size[0], min(W, crop_size[1])].
+          Then crop a region (H_crop, W_crop).
+        """
+        # TODO style of relative_range and absolute_range are not consistent:
+        # one takes (h, w) but another takes (min, max)
+        super().__init__()
+        assert crop_type in ["relative_range", "relative", "absolute", "absolute_range"]
+        self._init(locals())
+
+    def get_transform(self, image):
+        h, w = image.shape[:2]
+        croph, cropw = self.get_crop_size((h, w))
+        assert h >= croph and w >= cropw, "Shape computation in {} has bugs.".format(self)
+        h0 = np.random.randint(h - croph + 1)
+        w0 = np.random.randint(w - cropw + 1)
+        return CropTransform(w0, h0, cropw, croph)
+
+    def get_crop_size(self, image_size):
+        """
+        Args:
+            image_size (tuple): height, width
+
+        Returns:
+            crop_size (tuple): height, width in absolute pixels
+        """
+        h, w = image_size
+        if self.crop_type == "relative":
+            ch, cw = self.crop_size
+            return int(h * ch + 0.5), int(w * cw + 0.5)
+        elif self.crop_type == "relative_range":
+            crop_size = np.asarray(self.crop_size, dtype=np.float32)
+            ch, cw = crop_size + np.random.rand(2) * (1 - crop_size)
+            return int(h * ch + 0.5), int(w * cw + 0.5)
+        elif self.crop_type == "absolute":
+            return (min(self.crop_size[0], h), min(self.crop_size[1], w))
+        elif self.crop_type == "absolute_range":
+            assert self.crop_size[0] <= self.crop_size[1]
+            ch = np.random.randint(min(h, self.crop_size[0]), min(h, self.crop_size[1]) + 1)
+            cw = np.random.randint(min(w, self.crop_size[0]), min(w, self.crop_size[1]) + 1)
+            return ch, cw
+        else:
+            raise NotImplementedError("Unknown crop type {}".format(self.crop_type))
+
+
+class RandomCrop_CategoryAreaConstraint(Augmentation):
+    """
+    Similar to :class:`RandomCrop`, but find a cropping window such that no single category
+    occupies a ratio of more than `single_category_max_area` in semantic segmentation ground
+    truth, which can cause unstability in training. The function attempts to find such a valid
+    cropping window for at most 10 times.
+    """
+
+    def __init__(
+        self,
+        crop_type: str,
+        crop_size,
+        single_category_max_area: float = 1.0,
+        ignored_category: int = None,
+    ):
+        """
+        Args:
+            crop_type, crop_size: same as in :class:`RandomCrop`
+            single_category_max_area: the maximum allowed area ratio of a
+                category. Set to 1.0 to disable
+            ignored_category: allow this category in the semantic segmentation
+                ground truth to exceed the area ratio. Usually set to the category
+                that's ignored in training.
+        """
+        self.crop_aug = RandomCrop(crop_type, crop_size)
+        self._init(locals())
+
+    def get_transform(self, image, sem_seg):
+        if self.single_category_max_area >= 1.0:
+            return self.crop_aug.get_transform(image)
+        else:
+            h, w = sem_seg.shape
+            for _ in range(10):
+                crop_size = self.crop_aug.get_crop_size((h, w))
+                y0 = np.random.randint(h - crop_size[0] + 1)
+                x0 = np.random.randint(w - crop_size[1] + 1)
+                sem_seg_temp = sem_seg[y0 : y0 + crop_size[0], x0 : x0 + crop_size[1]]
+                labels, cnt = np.unique(sem_seg_temp, return_counts=True)
+                if self.ignored_category is not None:
+                    cnt = cnt[labels != self.ignored_category]
+                if len(cnt) > 1 and np.max(cnt) < np.sum(cnt) * self.single_category_max_area:
+                    break
+            crop_tfm = CropTransform(x0, y0, crop_size[1], crop_size[0])
+            return crop_tfm
+
+
+class RandomExtent(Augmentation):
+    """
+    Outputs an image by cropping a random "subrect" of the source image.
+
+    The subrect can be parameterized to include pixels outside the source image,
+    in which case they will be set to zeros (i.e. black). The size of the output
+    image will vary with the size of the random subrect.
+    """
+
+    def __init__(self, scale_range, shift_range):
+        """
+        Args:
+            output_size (h, w): Dimensions of output image
+            scale_range (l, h): Range of input-to-output size scaling factor
+            shift_range (x, y): Range of shifts of the cropped subrect. The rect
+                is shifted by [w / 2 * Uniform(-x, x), h / 2 * Uniform(-y, y)],
+                where (w, h) is the (width, height) of the input image. Set each
+                component to zero to crop at the image's center.
+        """
+        super().__init__()
+        self._init(locals())
+
+    def get_transform(self, image):
+        img_h, img_w = image.shape[:2]
+
+        # Initialize src_rect to fit the input image.
+        src_rect = np.array([-0.5 * img_w, -0.5 * img_h, 0.5 * img_w, 0.5 * img_h])
+
+        # Apply a random scaling to the src_rect.
+        src_rect *= np.random.uniform(self.scale_range[0], self.scale_range[1])
+
+        # Apply a random shift to the coordinates origin.
+        src_rect[0::2] += self.shift_range[0] * img_w * (np.random.rand() - 0.5)
+        src_rect[1::2] += self.shift_range[1] * img_h * (np.random.rand() - 0.5)
+
+        # Map src_rect coordinates into image coordinates (center at corner).
+        src_rect[0::2] += 0.5 * img_w
+        src_rect[1::2] += 0.5 * img_h
+
+        return ExtentTransform(
+            src_rect=(src_rect[0], src_rect[1], src_rect[2], src_rect[3]),
+            output_size=(int(src_rect[3] - src_rect[1]), int(src_rect[2] - src_rect[0])),
+        )
+
+
+class RandomContrast(Augmentation):
+    """
+    Randomly transforms image contrast.
+
+    Contrast intensity is uniformly sampled in (intensity_min, intensity_max).
+    - intensity < 1 will reduce contrast
+    - intensity = 1 will preserve the input image
+    - intensity > 1 will increase contrast
+
+    See: https://pillow.readthedocs.io/en/3.0.x/reference/ImageEnhance.html
+    """
+
+    def __init__(self, intensity_min, intensity_max):
+        """
+        Args:
+            intensity_min (float): Minimum augmentation
+            intensity_max (float): Maximum augmentation
+        """
+        super().__init__()
+        self._init(locals())
+
+    def get_transform(self, image):
+        w = np.random.uniform(self.intensity_min, self.intensity_max)
+        return BlendTransform(src_image=image.mean(), src_weight=1 - w, dst_weight=w)
+
+
+class RandomBrightness(Augmentation):
+    """
+    Randomly transforms image brightness.
+
+    Brightness intensity is uniformly sampled in (intensity_min, intensity_max).
+    - intensity < 1 will reduce brightness
+    - intensity = 1 will preserve the input image
+    - intensity > 1 will increase brightness
+
+    See: https://pillow.readthedocs.io/en/3.0.x/reference/ImageEnhance.html
+    """
+
+    def __init__(self, intensity_min, intensity_max):
+        """
+        Args:
+            intensity_min (float): Minimum augmentation
+            intensity_max (float): Maximum augmentation
+        """
+        super().__init__()
+        self._init(locals())
+
+    def get_transform(self, image):
+        w = np.random.uniform(self.intensity_min, self.intensity_max)
+        return BlendTransform(src_image=0, src_weight=1 - w, dst_weight=w)
+
+
+class RandomSaturation(Augmentation):
+    """
+    Randomly transforms saturation of an RGB image.
+    Input images are assumed to have 'RGB' channel order.
+
+    Saturation intensity is uniformly sampled in (intensity_min, intensity_max).
+    - intensity < 1 will reduce saturation (make the image more grayscale)
+    - intensity = 1 will preserve the input image
+    - intensity > 1 will increase saturation
+
+    See: https://pillow.readthedocs.io/en/3.0.x/reference/ImageEnhance.html
+    """
+
+    def __init__(self, intensity_min, intensity_max):
+        """
+        Args:
+            intensity_min (float): Minimum augmentation (1 preserves input).
+            intensity_max (float): Maximum augmentation (1 preserves input).
+        """
+        super().__init__()
+        self._init(locals())
+
+    def get_transform(self, image):
+        assert image.shape[-1] == 3, "RandomSaturation only works on RGB images"
+        w = np.random.uniform(self.intensity_min, self.intensity_max)
+        grayscale = image.dot([0.299, 0.587, 0.114])[:, :, np.newaxis]
+        return BlendTransform(src_image=grayscale, src_weight=1 - w, dst_weight=w)
+
+
+class RandomLighting(Augmentation):
+    """
+    The "lighting" augmentation described in AlexNet, using fixed PCA over ImageNet.
+    Input images are assumed to have 'RGB' channel order.
+
+    The degree of color jittering is randomly sampled via a normal distribution,
+    with standard deviation given by the scale parameter.
+    """
+
+    def __init__(self, scale):
+        """
+        Args:
+            scale (float): Standard deviation of principal component weighting.
+        """
+        super().__init__()
+        self._init(locals())
+        self.eigen_vecs = np.array(
+            [[-0.5675, 0.7192, 0.4009], [-0.5808, -0.0045, -0.8140], [-0.5836, -0.6948, 0.4203]]
+        )
+        self.eigen_vals = np.array([0.2175, 0.0188, 0.0045])
+
+    def get_transform(self, image):
+        assert image.shape[-1] == 3, "RandomLighting only works on RGB images"
+        weights = np.random.normal(scale=self.scale, size=3)
+        return BlendTransform(
+            src_image=self.eigen_vecs.dot(weights * self.eigen_vals), src_weight=1.0, dst_weight=1.0
+        )
+
+
+class RandomResize(Augmentation):
+    """Randomly resize image to a target size in shape_list"""
+
+    def __init__(self, shape_list, interp=Image.BILINEAR):
+        """
+        Args:
+            shape_list: a list of shapes in (h, w)
+            interp: PIL interpolation method
+        """
+        self.shape_list = shape_list
+        self._init(locals())
+
+    def get_transform(self, image):
+        shape_idx = np.random.randint(low=0, high=len(self.shape_list))
+        h, w = self.shape_list[shape_idx]
+        return ResizeTransform(image.shape[0], image.shape[1], h, w, self.interp)
+
+
+class MinIoURandomCrop(Augmentation):
+    """Random crop the image & bboxes, the cropped patches have minimum IoU
+    requirement with original image & bboxes, the IoU threshold is randomly
+    selected from min_ious.
+
+    Args:
+        min_ious (tuple): minimum IoU threshold for all intersections with
+        bounding boxes
+        min_crop_size (float): minimum crop's size (i.e. h,w := a*h, a*w,
+        where a >= min_crop_size)
+        mode_trials: number of trials for sampling min_ious threshold
+        crop_trials: number of trials for sampling crop_size after cropping
+    """
+
+    def __init__(
+        self,
+        min_ious=(0.1, 0.3, 0.5, 0.7, 0.9),
+        min_crop_size=0.3,
+        mode_trials=1000,
+        crop_trials=50,
+    ):
+        self.min_ious = min_ious
+        self.sample_mode = (1, *min_ious, 0)
+        self.min_crop_size = min_crop_size
+        self.mode_trials = mode_trials
+        self.crop_trials = crop_trials
+
+    def get_transform(self, image, boxes):
+        """Call function to crop images and bounding boxes with minimum IoU
+        constraint.
+
+        Args:
+            boxes: ground truth boxes in (x1, y1, x2, y2) format
+        """
+        if boxes is None:
+            return NoOpTransform()
+        h, w, c = image.shape
+        for _ in range(self.mode_trials):
+            mode = random.choice(self.sample_mode)
+            self.mode = mode
+            if mode == 1:
+                return NoOpTransform()
+
+            min_iou = mode
+            for _ in range(self.crop_trials):
+                new_w = random.uniform(self.min_crop_size * w, w)
+                new_h = random.uniform(self.min_crop_size * h, h)
+
+                # h / w in [0.5, 2]
+                if new_h / new_w < 0.5 or new_h / new_w > 2:
+                    continue
+
+                left = random.uniform(w - new_w)
+                top = random.uniform(h - new_h)
+
+                patch = np.array((int(left), int(top), int(left + new_w), int(top + new_h)))
+                # Line or point crop is not allowed
+                if patch[2] == patch[0] or patch[3] == patch[1]:
+                    continue
+                overlaps = pairwise_iou(
+                    Boxes(patch.reshape(-1, 4)), Boxes(boxes.reshape(-1, 4))
+                ).reshape(-1)
+                if len(overlaps) > 0 and overlaps.min() < min_iou:
+                    continue
+
+                # center of boxes should inside the crop img
+                # only adjust boxes and instance masks when the gt is not empty
+                if len(overlaps) > 0:
+                    # adjust boxes
+                    def is_center_of_bboxes_in_patch(boxes, patch):
+                        center = (boxes[:, :2] + boxes[:, 2:]) / 2
+                        mask = (
+                            (center[:, 0] > patch[0])
+                            * (center[:, 1] > patch[1])
+                            * (center[:, 0] < patch[2])
+                            * (center[:, 1] < patch[3])
+                        )
+                        return mask
+
+                    mask = is_center_of_bboxes_in_patch(boxes, patch)
+                    if not mask.any():
+                        continue
+                return CropTransform(int(left), int(top), int(new_w), int(new_h))

detectron2/data/transforms/transform.py

@@ -0,0 +1,351 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+"""
+See "Data Augmentation" tutorial for an overview of the system:
+https://detectron2.readthedocs.io/tutorials/augmentation.html
+"""
+
+import numpy as np
+import torch
+import torch.nn.functional as F
+from fvcore.transforms.transform import (
+    CropTransform,
+    HFlipTransform,
+    NoOpTransform,
+    Transform,
+    TransformList,
+)
+from PIL import Image
+
+try:
+    import cv2  # noqa
+except ImportError:
+    # OpenCV is an optional dependency at the moment
+    pass
+
+__all__ = [
+    "ExtentTransform",
+    "ResizeTransform",
+    "RotationTransform",
+    "ColorTransform",
+    "PILColorTransform",
+]
+
+
+class ExtentTransform(Transform):
+    """
+    Extracts a subregion from the source image and scales it to the output size.
+
+    The fill color is used to map pixels from the source rect that fall outside
+    the source image.
+
+    See: https://pillow.readthedocs.io/en/latest/PIL.html#PIL.ImageTransform.ExtentTransform
+    """
+
+    def __init__(self, src_rect, output_size, interp=Image.BILINEAR, fill=0):
+        """
+        Args:
+            src_rect (x0, y0, x1, y1): src coordinates
+            output_size (h, w): dst image size
+            interp: PIL interpolation methods
+            fill: Fill color used when src_rect extends outside image
+        """
+        super().__init__()
+        self._set_attributes(locals())
+
+    def apply_image(self, img, interp=None):
+        h, w = self.output_size
+        if len(img.shape) > 2 and img.shape[2] == 1:
+            pil_image = Image.fromarray(img[:, :, 0], mode="L")
+        else:
+            pil_image = Image.fromarray(img)
+        pil_image = pil_image.transform(
+            size=(w, h),
+            method=Image.EXTENT,
+            data=self.src_rect,
+            resample=interp if interp else self.interp,
+            fill=self.fill,
+        )
+        ret = np.asarray(pil_image)
+        if len(img.shape) > 2 and img.shape[2] == 1:
+            ret = np.expand_dims(ret, -1)
+        return ret
+
+    def apply_coords(self, coords):
+        # Transform image center from source coordinates into output coordinates
+        # and then map the new origin to the corner of the output image.
+        h, w = self.output_size
+        x0, y0, x1, y1 = self.src_rect
+        new_coords = coords.astype(np.float32)
+        new_coords[:, 0] -= 0.5 * (x0 + x1)
+        new_coords[:, 1] -= 0.5 * (y0 + y1)
+        new_coords[:, 0] *= w / (x1 - x0)
+        new_coords[:, 1] *= h / (y1 - y0)
+        new_coords[:, 0] += 0.5 * w
+        new_coords[:, 1] += 0.5 * h
+        return new_coords
+
+    def apply_segmentation(self, segmentation):
+        segmentation = self.apply_image(segmentation, interp=Image.NEAREST)
+        return segmentation
+
+
+class ResizeTransform(Transform):
+    """
+    Resize the image to a target size.
+    """
+
+    def __init__(self, h, w, new_h, new_w, interp=None):
+        """
+        Args:
+            h, w (int): original image size
+            new_h, new_w (int): new image size
+            interp: PIL interpolation methods, defaults to bilinear.
+        """
+        # TODO decide on PIL vs opencv
+        super().__init__()
+        if interp is None:
+            interp = Image.BILINEAR
+        self._set_attributes(locals())
+
+    def apply_image(self, img, interp=None):
+        assert img.shape[:2] == (self.h, self.w)
+        assert len(img.shape) <= 4
+        interp_method = interp if interp is not None else self.interp
+
+        if img.dtype == np.uint8:
+            if len(img.shape) > 2 and img.shape[2] == 1:
+                pil_image = Image.fromarray(img[:, :, 0], mode="L")
+            else:
+                pil_image = Image.fromarray(img)
+            pil_image = pil_image.resize((self.new_w, self.new_h), interp_method)
+            ret = np.asarray(pil_image)
+            if len(img.shape) > 2 and img.shape[2] == 1:
+                ret = np.expand_dims(ret, -1)
+        else:
+            # PIL only supports uint8
+            if any(x < 0 for x in img.strides):
+                img = np.ascontiguousarray(img)
+            img = torch.from_numpy(img)
+            shape = list(img.shape)
+            shape_4d = shape[:2] + [1] * (4 - len(shape)) + shape[2:]
+            img = img.view(shape_4d).permute(2, 3, 0, 1)  # hw(c) -> nchw
+            _PIL_RESIZE_TO_INTERPOLATE_MODE = {
+                Image.NEAREST: "nearest",
+                Image.BILINEAR: "bilinear",
+                Image.BICUBIC: "bicubic",
+            }
+            mode = _PIL_RESIZE_TO_INTERPOLATE_MODE[interp_method]
+            align_corners = None if mode == "nearest" else False
+            img = F.interpolate(
+                img, (self.new_h, self.new_w), mode=mode, align_corners=align_corners
+            )
+            shape[:2] = (self.new_h, self.new_w)
+            ret = img.permute(2, 3, 0, 1).view(shape).numpy()  # nchw -> hw(c)
+
+        return ret
+
+    def apply_coords(self, coords):
+        coords[:, 0] = coords[:, 0] * (self.new_w * 1.0 / self.w)
+        coords[:, 1] = coords[:, 1] * (self.new_h * 1.0 / self.h)
+        return coords
+
+    def apply_segmentation(self, segmentation):
+        segmentation = self.apply_image(segmentation, interp=Image.NEAREST)
+        return segmentation
+
+    def inverse(self):
+        return ResizeTransform(self.new_h, self.new_w, self.h, self.w, self.interp)
+
+
+class RotationTransform(Transform):
+    """
+    This method returns a copy of this image, rotated the given
+    number of degrees counter clockwise around its center.
+    """
+
+    def __init__(self, h, w, angle, expand=True, center=None, interp=None):
+        """
+        Args:
+            h, w (int): original image size
+            angle (float): degrees for rotation
+            expand (bool): choose if the image should be resized to fit the whole
+                rotated image (default), or simply cropped
+            center (tuple (width, height)): coordinates of the rotation center
+                if left to None, the center will be fit to the center of each image
+                center has no effect if expand=True because it only affects shifting
+            interp: cv2 interpolation method, default cv2.INTER_LINEAR
+        """
+        super().__init__()
+        image_center = np.array((w / 2, h / 2))
+        if center is None:
+            center = image_center
+        if interp is None:
+            interp = cv2.INTER_LINEAR
+        abs_cos, abs_sin = (abs(np.cos(np.deg2rad(angle))), abs(np.sin(np.deg2rad(angle))))
+        if expand:
+            # find the new width and height bounds
+            bound_w, bound_h = np.rint(
+                [h * abs_sin + w * abs_cos, h * abs_cos + w * abs_sin]
+            ).astype(int)
+        else:
+            bound_w, bound_h = w, h
+
+        self._set_attributes(locals())
+        self.rm_coords = self.create_rotation_matrix()
+        # Needed because of this problem https://github.com/opencv/opencv/issues/11784
+        self.rm_image = self.create_rotation_matrix(offset=-0.5)
+
+    def apply_image(self, img, interp=None):
+        """
+        img should be a numpy array, formatted as Height * Width * Nchannels
+        """
+        if len(img) == 0 or self.angle % 360 == 0:
+            return img
+        assert img.shape[:2] == (self.h, self.w)
+        interp = interp if interp is not None else self.interp
+        return cv2.warpAffine(img, self.rm_image, (self.bound_w, self.bound_h), flags=interp)
+
+    def apply_coords(self, coords):
+        """
+        coords should be a N * 2 array-like, containing N couples of (x, y) points
+        """
+        coords = np.asarray(coords, dtype=float)
+        if len(coords) == 0 or self.angle % 360 == 0:
+            return coords
+        return cv2.transform(coords[:, np.newaxis, :], self.rm_coords)[:, 0, :]
+
+    def apply_segmentation(self, segmentation):
+        segmentation = self.apply_image(segmentation, interp=cv2.INTER_NEAREST)
+        return segmentation
+
+    def create_rotation_matrix(self, offset=0):
+        center = (self.center[0] + offset, self.center[1] + offset)
+        rm = cv2.getRotationMatrix2D(tuple(center), self.angle, 1)
+        if self.expand:
+            # Find the coordinates of the center of rotation in the new image
+            # The only point for which we know the future coordinates is the center of the image
+            rot_im_center = cv2.transform(self.image_center[None, None, :] + offset, rm)[0, 0, :]
+            new_center = np.array([self.bound_w / 2, self.bound_h / 2]) + offset - rot_im_center
+            # shift the rotation center to the new coordinates
+            rm[:, 2] += new_center
+        return rm
+
+    def inverse(self):
+        """
+        The inverse is to rotate it back with expand, and crop to get the original shape.
+        """
+        if not self.expand:  # Not possible to inverse if a part of the image is lost
+            raise NotImplementedError()
+        rotation = RotationTransform(
+            self.bound_h, self.bound_w, -self.angle, True, None, self.interp
+        )
+        crop = CropTransform(
+            (rotation.bound_w - self.w) // 2, (rotation.bound_h - self.h) // 2, self.w, self.h
+        )
+        return TransformList([rotation, crop])
+
+
+class ColorTransform(Transform):
+    """
+    Generic wrapper for any photometric transforms.
+    These transformations should only affect the color space and
+        not the coordinate space of the image (e.g. annotation
+        coordinates such as bounding boxes should not be changed)
+    """
+
+    def __init__(self, op):
+        """
+        Args:
+            op (Callable): operation to be applied to the image,
+                which takes in an ndarray and returns an ndarray.
+        """
+        if not callable(op):
+            raise ValueError("op parameter should be callable")
+        super().__init__()
+        self._set_attributes(locals())
+
+    def apply_image(self, img):
+        return self.op(img)
+
+    def apply_coords(self, coords):
+        return coords
+
+    def inverse(self):
+        return NoOpTransform()
+
+    def apply_segmentation(self, segmentation):
+        return segmentation
+
+
+class PILColorTransform(ColorTransform):
+    """
+    Generic wrapper for PIL Photometric image transforms,
+        which affect the color space and not the coordinate
+        space of the image
+    """
+
+    def __init__(self, op):
+        """
+        Args:
+            op (Callable): operation to be applied to the image,
+                which takes in a PIL Image and returns a transformed
+                PIL Image.
+                For reference on possible operations see:
+                - https://pillow.readthedocs.io/en/stable/
+        """
+        if not callable(op):
+            raise ValueError("op parameter should be callable")
+        super().__init__(op)
+
+    def apply_image(self, img):
+        img = Image.fromarray(img)
+        return np.asarray(super().apply_image(img))
+
+
+def HFlip_rotated_box(transform, rotated_boxes):
+    """
+    Apply the horizontal flip transform on rotated boxes.
+
+    Args:
+        rotated_boxes (ndarray): Nx5 floating point array of
+            (x_center, y_center, width, height, angle_degrees) format
+            in absolute coordinates.
+    """
+    # Transform x_center
+    rotated_boxes[:, 0] = transform.width - rotated_boxes[:, 0]
+    # Transform angle
+    rotated_boxes[:, 4] = -rotated_boxes[:, 4]
+    return rotated_boxes
+
+
+def Resize_rotated_box(transform, rotated_boxes):
+    """
+    Apply the resizing transform on rotated boxes. For details of how these (approximation)
+    formulas are derived, please refer to :meth:`RotatedBoxes.scale`.
+
+    Args:
+        rotated_boxes (ndarray): Nx5 floating point array of
+            (x_center, y_center, width, height, angle_degrees) format
+            in absolute coordinates.
+    """
+    scale_factor_x = transform.new_w * 1.0 / transform.w
+    scale_factor_y = transform.new_h * 1.0 / transform.h
+    rotated_boxes[:, 0] *= scale_factor_x
+    rotated_boxes[:, 1] *= scale_factor_y
+    theta = rotated_boxes[:, 4] * np.pi / 180.0
+    c = np.cos(theta)
+    s = np.sin(theta)
+    rotated_boxes[:, 2] *= np.sqrt(np.square(scale_factor_x * c) + np.square(scale_factor_y * s))
+    rotated_boxes[:, 3] *= np.sqrt(np.square(scale_factor_x * s) + np.square(scale_factor_y * c))
+    rotated_boxes[:, 4] = np.arctan2(scale_factor_x * s, scale_factor_y * c) * 180 / np.pi
+
+    return rotated_boxes
+
+
+HFlipTransform.register_type("rotated_box", HFlip_rotated_box)
+ResizeTransform.register_type("rotated_box", Resize_rotated_box)
+
+# not necessary any more with latest fvcore
+NoOpTransform.register_type("rotated_box", lambda t, x: x)

detectron2/engine/__init__.py

@@ -0,0 +1,19 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+from .launch import *
+from .train_loop import *
+
+__all__ = [k for k in globals().keys() if not k.startswith("_")]
+
+
+# prefer to let hooks and defaults live in separate namespaces (therefore not in __all__)
+# but still make them available here
+from .hooks import *
+from .defaults import (
+    create_ddp_model,
+    default_argument_parser,
+    default_setup,
+    default_writers,
+    DefaultPredictor,
+    DefaultTrainer,
+)

detectron2/engine/defaults.py

@@ -0,0 +1,719 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+"""
+This file contains components with some default boilerplate logic user may need
+in training / testing. They will not work for everyone, but many users may find them useful.
+
+The behavior of functions/classes in this file is subject to change,
+since they are meant to represent the "common default behavior" people need in their projects.
+"""
+
+import argparse
+import logging
+import os
+import sys
+import weakref
+from collections import OrderedDict
+from typing import Optional
+import torch
+from fvcore.nn.precise_bn import get_bn_modules
+from omegaconf import OmegaConf
+from torch.nn.parallel import DistributedDataParallel
+
+import detectron2.data.transforms as T
+from detectron2.checkpoint import DetectionCheckpointer
+from detectron2.config import CfgNode, LazyConfig
+from detectron2.data import (
+    MetadataCatalog,
+    build_detection_test_loader,
+    build_detection_train_loader,
+)
+from detectron2.evaluation import (
+    DatasetEvaluator,
+    inference_on_dataset,
+    print_csv_format,
+    verify_results,
+)
+from detectron2.modeling import build_model
+from detectron2.solver import build_lr_scheduler, build_optimizer
+from detectron2.utils import comm
+from detectron2.utils.collect_env import collect_env_info
+from detectron2.utils.env import seed_all_rng
+from detectron2.utils.events import CommonMetricPrinter, JSONWriter, TensorboardXWriter
+from detectron2.utils.file_io import PathManager
+from detectron2.utils.logger import setup_logger
+
+from . import hooks
+from .train_loop import AMPTrainer, SimpleTrainer, TrainerBase
+
+__all__ = [
+    "create_ddp_model",
+    "default_argument_parser",
+    "default_setup",
+    "default_writers",
+    "DefaultPredictor",
+    "DefaultTrainer",
+]
+
+
+def create_ddp_model(model, *, fp16_compression=False, **kwargs):
+    """
+    Create a DistributedDataParallel model if there are >1 processes.
+
+    Args:
+        model: a torch.nn.Module
+        fp16_compression: add fp16 compression hooks to the ddp object.
+            See more at https://pytorch.org/docs/stable/ddp_comm_hooks.html#torch.distributed.algorithms.ddp_comm_hooks.default_hooks.fp16_compress_hook
+        kwargs: other arguments of :module:`torch.nn.parallel.DistributedDataParallel`.
+    """  # noqa
+    if comm.get_world_size() == 1:
+        return model
+    if "device_ids" not in kwargs:
+        kwargs["device_ids"] = [comm.get_local_rank()]
+    ddp = DistributedDataParallel(model, **kwargs)
+    if fp16_compression:
+        from torch.distributed.algorithms.ddp_comm_hooks import default as comm_hooks
+
+        ddp.register_comm_hook(state=None, hook=comm_hooks.fp16_compress_hook)
+    return ddp
+
+
+def default_argument_parser(epilog=None):
+    """
+    Create a parser with some common arguments used by detectron2 users.
+
+    Args:
+        epilog (str): epilog passed to ArgumentParser describing the usage.
+
+    Returns:
+        argparse.ArgumentParser:
+    """
+    parser = argparse.ArgumentParser(
+        epilog=epilog
+        or f"""
+Examples:
+
+Run on single machine:
+    $ {sys.argv[0]} --num-gpus 8 --config-file cfg.yaml
+
+Change some config options:
+    $ {sys.argv[0]} --config-file cfg.yaml MODEL.WEIGHTS /path/to/weight.pth SOLVER.BASE_LR 0.001
+
+Run on multiple machines:
+    (machine0)$ {sys.argv[0]} --machine-rank 0 --num-machines 2 --dist-url <URL> [--other-flags]
+    (machine1)$ {sys.argv[0]} --machine-rank 1 --num-machines 2 --dist-url <URL> [--other-flags]
+""",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+    parser.add_argument("--config-file", default="", metavar="FILE", help="path to config file")
+    parser.add_argument(
+        "--resume",
+        action="store_true",
+        help="Whether to attempt to resume from the checkpoint directory. "
+        "See documentation of `DefaultTrainer.resume_or_load()` for what it means.",
+    )
+    parser.add_argument("--eval-only", action="store_true", help="perform evaluation only")
+    parser.add_argument("--num-gpus", type=int, default=1, help="number of gpus *per machine*")
+    parser.add_argument("--num-machines", type=int, default=1, help="total number of machines")
+    parser.add_argument(
+        "--machine-rank", type=int, default=0, help="the rank of this machine (unique per machine)"
+    )
+
+    # PyTorch still may leave orphan processes in multi-gpu training.
+    # Therefore we use a deterministic way to obtain port,
+    # so that users are aware of orphan processes by seeing the port occupied.
+    port = 2**15 + 2**14 + hash(os.getuid() if sys.platform != "win32" else 1) % 2**14
+    parser.add_argument(
+        "--dist-url",
+        default="tcp://127.0.0.1:{}".format(port),
+        help="initialization URL for pytorch distributed backend. See "
+        "https://pytorch.org/docs/stable/distributed.html for details.",
+    )
+    parser.add_argument(
+        "opts",
+        help="""
+Modify config options at the end of the command. For Yacs configs, use
+space-separated "PATH.KEY VALUE" pairs.
+For python-based LazyConfig, use "path.key=value".
+        """.strip(),
+        default=None,
+        nargs=argparse.REMAINDER,
+    )
+    return parser
+
+
+def _try_get_key(cfg, *keys, default=None):
+    """
+    Try select keys from cfg until the first key that exists. Otherwise return default.
+    """
+    if isinstance(cfg, CfgNode):
+        cfg = OmegaConf.create(cfg.dump())
+    for k in keys:
+        none = object()
+        p = OmegaConf.select(cfg, k, default=none)
+        if p is not none:
+            return p
+    return default
+
+
+def _highlight(code, filename):
+    try:
+        import pygments
+    except ImportError:
+        return code
+
+    from pygments.lexers import Python3Lexer, YamlLexer
+    from pygments.formatters import Terminal256Formatter
+
+    lexer = Python3Lexer() if filename.endswith(".py") else YamlLexer()
+    code = pygments.highlight(code, lexer, Terminal256Formatter(style="monokai"))
+    return code
+
+
+def default_setup(cfg, args):
+    """
+    Perform some basic common setups at the beginning of a job, including:
+
+    1. Set up the detectron2 logger
+    2. Log basic information about environment, cmdline arguments, and config
+    3. Backup the config to the output directory
+
+    Args:
+        cfg (CfgNode or omegaconf.DictConfig): the full config to be used
+        args (argparse.NameSpace): the command line arguments to be logged
+    """
+    output_dir = _try_get_key(cfg, "OUTPUT_DIR", "output_dir", "train.output_dir")
+    if comm.is_main_process() and output_dir:
+        PathManager.mkdirs(output_dir)
+
+    rank = comm.get_rank()
+    setup_logger(output_dir, distributed_rank=rank, name="fvcore")
+    logger = setup_logger(output_dir, distributed_rank=rank)
+
+    logger.info("Rank of current process: {}. World size: {}".format(rank, comm.get_world_size()))
+    logger.info("Environment info:\n" + collect_env_info())
+
+    logger.info("Command line arguments: " + str(args))
+    if hasattr(args, "config_file") and args.config_file != "":
+        logger.info(
+            "Contents of args.config_file={}:\n{}".format(
+                args.config_file,
+                _highlight(PathManager.open(args.config_file, "r").read(), args.config_file),
+            )
+        )
+
+    if comm.is_main_process() and output_dir:
+        # Note: some of our scripts may expect the existence of
+        # config.yaml in output directory
+        path = os.path.join(output_dir, "config.yaml")
+        if isinstance(cfg, CfgNode):
+            logger.info("Running with full config:\n{}".format(_highlight(cfg.dump(), ".yaml")))
+            with PathManager.open(path, "w") as f:
+                f.write(cfg.dump())
+        else:
+            LazyConfig.save(cfg, path)
+        logger.info("Full config saved to {}".format(path))
+
+    # make sure each worker has a different, yet deterministic seed if specified
+    seed = _try_get_key(cfg, "SEED", "train.seed", default=-1)
+    seed_all_rng(None if seed < 0 else seed + rank)
+
+    # cudnn benchmark has large overhead. It shouldn't be used considering the small size of
+    # typical validation set.
+    if not (hasattr(args, "eval_only") and args.eval_only):
+        torch.backends.cudnn.benchmark = _try_get_key(
+            cfg, "CUDNN_BENCHMARK", "train.cudnn_benchmark", default=False
+        )
+
+
+def default_writers(output_dir: str, max_iter: Optional[int] = None):
+    """
+    Build a list of :class:`EventWriter` to be used.
+    It now consists of a :class:`CommonMetricPrinter`,
+    :class:`TensorboardXWriter` and :class:`JSONWriter`.
+
+    Args:
+        output_dir: directory to store JSON metrics and tensorboard events
+        max_iter: the total number of iterations
+
+    Returns:
+        list[EventWriter]: a list of :class:`EventWriter` objects.
+    """
+    PathManager.mkdirs(output_dir)
+    return [
+        # It may not always print what you want to see, since it prints "common" metrics only.
+        CommonMetricPrinter(max_iter),
+        JSONWriter(os.path.join(output_dir, "metrics.json")),
+        TensorboardXWriter(output_dir),
+    ]
+
+
+class DefaultPredictor:
+    """
+    Create a simple end-to-end predictor with the given config that runs on
+    single device for a single input image.
+
+    Compared to using the model directly, this class does the following additions:
+
+    1. Load checkpoint from `cfg.MODEL.WEIGHTS`.
+    2. Always take BGR image as the input and apply conversion defined by `cfg.INPUT.FORMAT`.
+    3. Apply resizing defined by `cfg.INPUT.{MIN,MAX}_SIZE_TEST`.
+    4. Take one input image and produce a single output, instead of a batch.
+
+    This is meant for simple demo purposes, so it does the above steps automatically.
+    This is not meant for benchmarks or running complicated inference logic.
+    If you'd like to do anything more complicated, please refer to its source code as
+    examples to build and use the model manually.
+
+    Attributes:
+        metadata (Metadata): the metadata of the underlying dataset, obtained from
+            cfg.DATASETS.TEST.
+
+    Examples:
+    ::
+        pred = DefaultPredictor(cfg)
+        inputs = cv2.imread("input.jpg")
+        outputs = pred(inputs)
+    """
+
+    def __init__(self, cfg):
+        self.cfg = cfg.clone()  # cfg can be modified by model
+        self.model = build_model(self.cfg)
+        self.model.eval()
+        if len(cfg.DATASETS.TEST):
+            self.metadata = MetadataCatalog.get(cfg.DATASETS.TEST[0])
+
+        checkpointer = DetectionCheckpointer(self.model)
+        checkpointer.load(cfg.MODEL.WEIGHTS)
+
+        self.aug = T.ResizeShortestEdge(
+            [cfg.INPUT.MIN_SIZE_TEST, cfg.INPUT.MIN_SIZE_TEST], cfg.INPUT.MAX_SIZE_TEST
+        )
+
+        self.input_format = cfg.INPUT.FORMAT
+        assert self.input_format in ["RGB", "BGR"], self.input_format
+
+    def __call__(self, original_image):
+        """
+        Args:
+            original_image (np.ndarray): an image of shape (H, W, C) (in BGR order).
+
+        Returns:
+            predictions (dict):
+                the output of the model for one image only.
+                See :doc:`/tutorials/models` for details about the format.
+        """
+        with torch.no_grad():  # https://github.com/sphinx-doc/sphinx/issues/4258
+            # Apply pre-processing to image.
+            if self.input_format == "RGB":
+                # whether the model expects BGR inputs or RGB
+                original_image = original_image[:, :, ::-1]
+            height, width = original_image.shape[:2]
+            image = self.aug.get_transform(original_image).apply_image(original_image)
+            image = torch.as_tensor(image.astype("float32").transpose(2, 0, 1))
+            image.to(self.cfg.MODEL.DEVICE)
+
+            inputs = {"image": image, "height": height, "width": width}
+
+            predictions = self.model([inputs])[0]
+            return predictions
+
+
+class DefaultTrainer(TrainerBase):
+    """
+    A trainer with default training logic. It does the following:
+
+    1. Create a :class:`SimpleTrainer` using model, optimizer, dataloader
+       defined by the given config. Create a LR scheduler defined by the config.
+    2. Load the last checkpoint or `cfg.MODEL.WEIGHTS`, if exists, when
+       `resume_or_load` is called.
+    3. Register a few common hooks defined by the config.
+
+    It is created to simplify the **standard model training workflow** and reduce code boilerplate
+    for users who only need the standard training workflow, with standard features.
+    It means this class makes *many assumptions* about your training logic that
+    may easily become invalid in a new research. In fact, any assumptions beyond those made in the
+    :class:`SimpleTrainer` are too much for research.
+
+    The code of this class has been annotated about restrictive assumptions it makes.
+    When they do not work for you, you're encouraged to:
+
+    1. Overwrite methods of this class, OR:
+    2. Use :class:`SimpleTrainer`, which only does minimal SGD training and
+       nothing else. You can then add your own hooks if needed. OR:
+    3. Write your own training loop similar to `tools/plain_train_net.py`.
+
+    See the :doc:`/tutorials/training` tutorials for more details.
+
+    Note that the behavior of this class, like other functions/classes in
+    this file, is not stable, since it is meant to represent the "common default behavior".
+    It is only guaranteed to work well with the standard models and training workflow in detectron2.
+    To obtain more stable behavior, write your own training logic with other public APIs.
+
+    Examples:
+    ::
+        trainer = DefaultTrainer(cfg)
+        trainer.resume_or_load()  # load last checkpoint or MODEL.WEIGHTS
+        trainer.train()
+
+    Attributes:
+        scheduler:
+        checkpointer (DetectionCheckpointer):
+        cfg (CfgNode):
+    """
+
+    def __init__(self, cfg):
+        """
+        Args:
+            cfg (CfgNode):
+        """
+        super().__init__()
+        logger = logging.getLogger("detectron2")
+        if not logger.isEnabledFor(logging.INFO):  # setup_logger is not called for d2
+            setup_logger()
+        cfg = DefaultTrainer.auto_scale_workers(cfg, comm.get_world_size())
+
+        # Assume these objects must be constructed in this order.
+        model = self.build_model(cfg)
+        optimizer = self.build_optimizer(cfg, model)
+        data_loader = self.build_train_loader(cfg)
+
+        model = create_ddp_model(model, broadcast_buffers=False)
+        self._trainer = (AMPTrainer if cfg.SOLVER.AMP.ENABLED else SimpleTrainer)(
+            model, data_loader, optimizer
+        )
+
+        self.scheduler = self.build_lr_scheduler(cfg, optimizer)
+        self.checkpointer = DetectionCheckpointer(
+            # Assume you want to save checkpoints together with logs/statistics
+            model,
+            cfg.OUTPUT_DIR,
+            trainer=weakref.proxy(self),
+        )
+        self.start_iter = 0
+        self.max_iter = cfg.SOLVER.MAX_ITER
+        self.cfg = cfg
+
+        self.register_hooks(self.build_hooks())
+
+    def resume_or_load(self, resume=True):
+        """
+        If `resume==True` and `cfg.OUTPUT_DIR` contains the last checkpoint (defined by
+        a `last_checkpoint` file), resume from the file. Resuming means loading all
+        available states (eg. optimizer and scheduler) and update iteration counter
+        from the checkpoint. ``cfg.MODEL.WEIGHTS`` will not be used.
+
+        Otherwise, this is considered as an independent training. The method will load model
+        weights from the file `cfg.MODEL.WEIGHTS` (but will not load other states) and start
+        from iteration 0.
+
+        Args:
+            resume (bool): whether to do resume or not
+        """
+        self.checkpointer.resume_or_load(self.cfg.MODEL.WEIGHTS, resume=resume)
+        if resume and self.checkpointer.has_checkpoint():
+            # The checkpoint stores the training iteration that just finished, thus we start
+            # at the next iteration
+            self.start_iter = self.iter + 1
+
+    def build_hooks(self):
+        """
+        Build a list of default hooks, including timing, evaluation,
+        checkpointing, lr scheduling, precise BN, writing events.
+
+        Returns:
+            list[HookBase]:
+        """
+        cfg = self.cfg.clone()
+        cfg.defrost()
+        cfg.DATALOADER.NUM_WORKERS = 0  # save some memory and time for PreciseBN
+
+        ret = [
+            hooks.IterationTimer(),
+            hooks.LRScheduler(),
+            (
+                hooks.PreciseBN(
+                    # Run at the same freq as (but before) evaluation.
+                    cfg.TEST.EVAL_PERIOD,
+                    self.model,
+                    # Build a new data loader to not affect training
+                    self.build_train_loader(cfg),
+                    cfg.TEST.PRECISE_BN.NUM_ITER,
+                )
+                if cfg.TEST.PRECISE_BN.ENABLED and get_bn_modules(self.model)
+                else None
+            ),
+        ]
+
+        # Do PreciseBN before checkpointer, because it updates the model and need to
+        # be saved by checkpointer.
+        # This is not always the best: if checkpointing has a different frequency,
+        # some checkpoints may have more precise statistics than others.
+        if comm.is_main_process():
+            ret.append(hooks.PeriodicCheckpointer(self.checkpointer, cfg.SOLVER.CHECKPOINT_PERIOD))
+
+        def test_and_save_results():
+            self._last_eval_results = self.test(self.cfg, self.model)
+            return self._last_eval_results
+
+        # Do evaluation after checkpointer, because then if it fails,
+        # we can use the saved checkpoint to debug.
+        ret.append(hooks.EvalHook(cfg.TEST.EVAL_PERIOD, test_and_save_results))
+
+        if comm.is_main_process():
+            # Here the default print/log frequency of each writer is used.
+            # run writers in the end, so that evaluation metrics are written
+            ret.append(hooks.PeriodicWriter(self.build_writers(), period=20))
+        return ret
+
+    def build_writers(self):
+        """
+        Build a list of writers to be used using :func:`default_writers()`.
+        If you'd like a different list of writers, you can overwrite it in
+        your trainer.
+
+        Returns:
+            list[EventWriter]: a list of :class:`EventWriter` objects.
+        """
+        return default_writers(self.cfg.OUTPUT_DIR, self.max_iter)
+
+    def train(self):
+        """
+        Run training.
+
+        Returns:
+            OrderedDict of results, if evaluation is enabled. Otherwise None.
+        """
+        super().train(self.start_iter, self.max_iter)
+        if len(self.cfg.TEST.EXPECTED_RESULTS) and comm.is_main_process():
+            assert hasattr(
+                self, "_last_eval_results"
+            ), "No evaluation results obtained during training!"
+            verify_results(self.cfg, self._last_eval_results)
+            return self._last_eval_results
+
+    def run_step(self):
+        self._trainer.iter = self.iter
+        self._trainer.run_step()
+
+    def state_dict(self):
+        ret = super().state_dict()
+        ret["_trainer"] = self._trainer.state_dict()
+        return ret
+
+    def load_state_dict(self, state_dict):
+        super().load_state_dict(state_dict)
+        self._trainer.load_state_dict(state_dict["_trainer"])
+
+    @classmethod
+    def build_model(cls, cfg):
+        """
+        Returns:
+            torch.nn.Module:
+
+        It now calls :func:`detectron2.modeling.build_model`.
+        Overwrite it if you'd like a different model.
+        """
+        model = build_model(cfg)
+        logger = logging.getLogger(__name__)
+        logger.info("Model:\n{}".format(model))
+        return model
+
+    @classmethod
+    def build_optimizer(cls, cfg, model):
+        """
+        Returns:
+            torch.optim.Optimizer:
+
+        It now calls :func:`detectron2.solver.build_optimizer`.
+        Overwrite it if you'd like a different optimizer.
+        """
+        return build_optimizer(cfg, model)
+
+    @classmethod
+    def build_lr_scheduler(cls, cfg, optimizer):
+        """
+        It now calls :func:`detectron2.solver.build_lr_scheduler`.
+        Overwrite it if you'd like a different scheduler.
+        """
+        return build_lr_scheduler(cfg, optimizer)
+
+    @classmethod
+    def build_train_loader(cls, cfg):
+        """
+        Returns:
+            iterable
+
+        It now calls :func:`detectron2.data.build_detection_train_loader`.
+        Overwrite it if you'd like a different data loader.
+        """
+        return build_detection_train_loader(cfg)
+
+    @classmethod
+    def build_test_loader(cls, cfg, dataset_name):
+        """
+        Returns:
+            iterable
+
+        It now calls :func:`detectron2.data.build_detection_test_loader`.
+        Overwrite it if you'd like a different data loader.
+        """
+        return build_detection_test_loader(cfg, dataset_name)
+
+    @classmethod
+    def build_evaluator(cls, cfg, dataset_name):
+        """
+        Returns:
+            DatasetEvaluator or None
+
+        It is not implemented by default.
+        """
+        raise NotImplementedError(
+            """
+If you want DefaultTrainer to automatically run evaluation,
+please implement `build_evaluator()` in subclasses (see train_net.py for example).
+Alternatively, you can call evaluation functions yourself (see Colab balloon tutorial for example).
+"""
+        )
+
+    @classmethod
+    def test(cls, cfg, model, evaluators=None):
+        """
+        Evaluate the given model. The given model is expected to already contain
+        weights to evaluate.
+
+        Args:
+            cfg (CfgNode):
+            model (nn.Module):
+            evaluators (list[DatasetEvaluator] or None): if None, will call
+                :meth:`build_evaluator`. Otherwise, must have the same length as
+                ``cfg.DATASETS.TEST``.
+
+        Returns:
+            dict: a dict of result metrics
+        """
+        logger = logging.getLogger(__name__)
+        if isinstance(evaluators, DatasetEvaluator):
+            evaluators = [evaluators]
+        if evaluators is not None:
+            assert len(cfg.DATASETS.TEST) == len(evaluators), "{} != {}".format(
+                len(cfg.DATASETS.TEST), len(evaluators)
+            )
+
+        results = OrderedDict()
+        for idx, dataset_name in enumerate(cfg.DATASETS.TEST):
+            data_loader = cls.build_test_loader(cfg, dataset_name)
+            # When evaluators are passed in as arguments,
+            # implicitly assume that evaluators can be created before data_loader.
+            if evaluators is not None:
+                evaluator = evaluators[idx]
+            else:
+                try:
+                    evaluator = cls.build_evaluator(cfg, dataset_name)
+                except NotImplementedError:
+                    logger.warn(
+                        "No evaluator found. Use `DefaultTrainer.test(evaluators=)`, "
+                        "or implement its `build_evaluator` method."
+                    )
+                    results[dataset_name] = {}
+                    continue
+            results_i = inference_on_dataset(model, data_loader, evaluator)
+            results[dataset_name] = results_i
+            if comm.is_main_process():
+                assert isinstance(
+                    results_i, dict
+                ), "Evaluator must return a dict on the main process. Got {} instead.".format(
+                    results_i
+                )
+                logger.info("Evaluation results for {} in csv format:".format(dataset_name))
+                print_csv_format(results_i)
+
+        if len(results) == 1:
+            results = list(results.values())[0]
+        return results
+
+    @staticmethod
+    def auto_scale_workers(cfg, num_workers: int):
+        """
+        When the config is defined for certain number of workers (according to
+        ``cfg.SOLVER.REFERENCE_WORLD_SIZE``) that's different from the number of
+        workers currently in use, returns a new cfg where the total batch size
+        is scaled so that the per-GPU batch size stays the same as the
+        original ``IMS_PER_BATCH // REFERENCE_WORLD_SIZE``.
+
+        Other config options are also scaled accordingly:
+        * training steps and warmup steps are scaled inverse proportionally.
+        * learning rate are scaled proportionally, following :paper:`ImageNet in 1h`.
+
+        For example, with the original config like the following:
+
+        .. code-block:: yaml
+
+            IMS_PER_BATCH: 16
+            BASE_LR: 0.1
+            REFERENCE_WORLD_SIZE: 8
+            MAX_ITER: 5000
+            STEPS: (4000,)
+            CHECKPOINT_PERIOD: 1000
+
+        When this config is used on 16 GPUs instead of the reference number 8,
+        calling this method will return a new config with:
+
+        .. code-block:: yaml
+
+            IMS_PER_BATCH: 32
+            BASE_LR: 0.2
+            REFERENCE_WORLD_SIZE: 16
+            MAX_ITER: 2500
+            STEPS: (2000,)
+            CHECKPOINT_PERIOD: 500
+
+        Note that both the original config and this new config can be trained on 16 GPUs.
+        It's up to user whether to enable this feature (by setting ``REFERENCE_WORLD_SIZE``).
+
+        Returns:
+            CfgNode: a new config. Same as original if ``cfg.SOLVER.REFERENCE_WORLD_SIZE==0``.
+        """
+        old_world_size = cfg.SOLVER.REFERENCE_WORLD_SIZE
+        if old_world_size == 0 or old_world_size == num_workers:
+            return cfg
+        cfg = cfg.clone()
+        frozen = cfg.is_frozen()
+        cfg.defrost()
+
+        assert (
+            cfg.SOLVER.IMS_PER_BATCH % old_world_size == 0
+        ), "Invalid REFERENCE_WORLD_SIZE in config!"
+        scale = num_workers / old_world_size
+        bs = cfg.SOLVER.IMS_PER_BATCH = int(round(cfg.SOLVER.IMS_PER_BATCH * scale))
+        lr = cfg.SOLVER.BASE_LR = cfg.SOLVER.BASE_LR * scale
+        max_iter = cfg.SOLVER.MAX_ITER = int(round(cfg.SOLVER.MAX_ITER / scale))
+        warmup_iter = cfg.SOLVER.WARMUP_ITERS = int(round(cfg.SOLVER.WARMUP_ITERS / scale))
+        cfg.SOLVER.STEPS = tuple(int(round(s / scale)) for s in cfg.SOLVER.STEPS)
+        cfg.TEST.EVAL_PERIOD = int(round(cfg.TEST.EVAL_PERIOD / scale))
+        cfg.SOLVER.CHECKPOINT_PERIOD = int(round(cfg.SOLVER.CHECKPOINT_PERIOD / scale))
+        cfg.SOLVER.REFERENCE_WORLD_SIZE = num_workers  # maintain invariant
+        logger = logging.getLogger(__name__)
+        logger.info(
+            f"Auto-scaling the config to batch_size={bs}, learning_rate={lr}, "
+            f"max_iter={max_iter}, warmup={warmup_iter}."
+        )
+
+        if frozen:
+            cfg.freeze()
+        return cfg
+
+
+# Access basic attributes from the underlying trainer
+for _attr in ["model", "data_loader", "optimizer"]:
+    setattr(
+        DefaultTrainer,
+        _attr,
+        property(
+            # getter
+            lambda self, x=_attr: getattr(self._trainer, x),
+            # setter
+            lambda self, value, x=_attr: setattr(self._trainer, x, value),
+        ),
+    )

detectron2/engine/hooks.py

@@ -0,0 +1,690 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+
+import datetime
+import itertools
+import logging
+import math
+import operator
+import os
+import tempfile
+import time
+import warnings
+from collections import Counter
+import torch
+from fvcore.common.checkpoint import Checkpointer
+from fvcore.common.checkpoint import PeriodicCheckpointer as _PeriodicCheckpointer
+from fvcore.common.param_scheduler import ParamScheduler
+from fvcore.common.timer import Timer
+from fvcore.nn.precise_bn import get_bn_modules, update_bn_stats
+
+import detectron2.utils.comm as comm
+from detectron2.evaluation.testing import flatten_results_dict
+from detectron2.solver import LRMultiplier
+from detectron2.solver import LRScheduler as _LRScheduler
+from detectron2.utils.events import EventStorage, EventWriter
+from detectron2.utils.file_io import PathManager
+
+from .train_loop import HookBase
+
+__all__ = [
+    "CallbackHook",
+    "IterationTimer",
+    "PeriodicWriter",
+    "PeriodicCheckpointer",
+    "BestCheckpointer",
+    "LRScheduler",
+    "AutogradProfiler",
+    "EvalHook",
+    "PreciseBN",
+    "TorchProfiler",
+    "TorchMemoryStats",
+]
+
+
+"""
+Implement some common hooks.
+"""
+
+
+class CallbackHook(HookBase):
+    """
+    Create a hook using callback functions provided by the user.
+    """
+
+    def __init__(self, *, before_train=None, after_train=None, before_step=None, after_step=None):
+        """
+        Each argument is a function that takes one argument: the trainer.
+        """
+        self._before_train = before_train
+        self._before_step = before_step
+        self._after_step = after_step
+        self._after_train = after_train
+
+    def before_train(self):
+        if self._before_train:
+            self._before_train(self.trainer)
+
+    def after_train(self):
+        if self._after_train:
+            self._after_train(self.trainer)
+        # The functions may be closures that hold reference to the trainer
+        # Therefore, delete them to avoid circular reference.
+        del self._before_train, self._after_train
+        del self._before_step, self._after_step
+
+    def before_step(self):
+        if self._before_step:
+            self._before_step(self.trainer)
+
+    def after_step(self):
+        if self._after_step:
+            self._after_step(self.trainer)
+
+
+class IterationTimer(HookBase):
+    """
+    Track the time spent for each iteration (each run_step call in the trainer).
+    Print a summary in the end of training.
+
+    This hook uses the time between the call to its :meth:`before_step`
+    and :meth:`after_step` methods.
+    Under the convention that :meth:`before_step` of all hooks should only
+    take negligible amount of time, the :class:`IterationTimer` hook should be
+    placed at the beginning of the list of hooks to obtain accurate timing.
+    """
+
+    def __init__(self, warmup_iter=3):
+        """
+        Args:
+            warmup_iter (int): the number of iterations at the beginning to exclude
+                from timing.
+        """
+        self._warmup_iter = warmup_iter
+        self._step_timer = Timer()
+        self._start_time = time.perf_counter()
+        self._total_timer = Timer()
+
+    def before_train(self):
+        self._start_time = time.perf_counter()
+        self._total_timer.reset()
+        self._total_timer.pause()
+
+    def after_train(self):
+        logger = logging.getLogger(__name__)
+        total_time = time.perf_counter() - self._start_time
+        total_time_minus_hooks = self._total_timer.seconds()
+        hook_time = total_time - total_time_minus_hooks
+
+        num_iter = self.trainer.storage.iter + 1 - self.trainer.start_iter - self._warmup_iter
+
+        if num_iter > 0 and total_time_minus_hooks > 0:
+            # Speed is meaningful only after warmup
+            # NOTE this format is parsed by grep in some scripts
+            logger.info(
+                "Overall training speed: {} iterations in {} ({:.4f} s / it)".format(
+                    num_iter,
+                    str(datetime.timedelta(seconds=int(total_time_minus_hooks))),
+                    total_time_minus_hooks / num_iter,
+                )
+            )
+
+        logger.info(
+            "Total training time: {} ({} on hooks)".format(
+                str(datetime.timedelta(seconds=int(total_time))),
+                str(datetime.timedelta(seconds=int(hook_time))),
+            )
+        )
+
+    def before_step(self):
+        self._step_timer.reset()
+        self._total_timer.resume()
+
+    def after_step(self):
+        # +1 because we're in after_step, the current step is done
+        # but not yet counted
+        iter_done = self.trainer.storage.iter - self.trainer.start_iter + 1
+        if iter_done >= self._warmup_iter:
+            sec = self._step_timer.seconds()
+            self.trainer.storage.put_scalars(time=sec)
+        else:
+            self._start_time = time.perf_counter()
+            self._total_timer.reset()
+
+        self._total_timer.pause()
+
+
+class PeriodicWriter(HookBase):
+    """
+    Write events to EventStorage (by calling ``writer.write()``) periodically.
+
+    It is executed every ``period`` iterations and after the last iteration.
+    Note that ``period`` does not affect how data is smoothed by each writer.
+    """
+
+    def __init__(self, writers, period=20):
+        """
+        Args:
+            writers (list[EventWriter]): a list of EventWriter objects
+            period (int):
+        """
+        self._writers = writers
+        for w in writers:
+            assert isinstance(w, EventWriter), w
+        self._period = period
+
+    def after_step(self):
+        if (self.trainer.iter + 1) % self._period == 0 or (
+            self.trainer.iter == self.trainer.max_iter - 1
+        ):
+            for writer in self._writers:
+                writer.write()
+
+    def after_train(self):
+        for writer in self._writers:
+            # If any new data is found (e.g. produced by other after_train),
+            # write them before closing
+            writer.write()
+            writer.close()
+
+
+class PeriodicCheckpointer(_PeriodicCheckpointer, HookBase):
+    """
+    Same as :class:`detectron2.checkpoint.PeriodicCheckpointer`, but as a hook.
+
+    Note that when used as a hook,
+    it is unable to save additional data other than what's defined
+    by the given `checkpointer`.
+
+    It is executed every ``period`` iterations and after the last iteration.
+    """
+
+    def before_train(self):
+        self.max_iter = self.trainer.max_iter
+
+    def after_step(self):
+        # No way to use **kwargs
+        self.step(self.trainer.iter)
+
+
+class BestCheckpointer(HookBase):
+    """
+    Checkpoints best weights based off given metric.
+
+    This hook should be used in conjunction to and executed after the hook
+    that produces the metric, e.g. `EvalHook`.
+    """
+
+    def __init__(
+        self,
+        eval_period: int,
+        checkpointer: Checkpointer,
+        val_metric: str,
+        mode: str = "max",
+        file_prefix: str = "model_best",
+    ) -> None:
+        """
+        Args:
+            eval_period (int): the period `EvalHook` is set to run.
+            checkpointer: the checkpointer object used to save checkpoints.
+            val_metric (str): validation metric to track for best checkpoint, e.g. "bbox/AP50"
+            mode (str): one of {'max', 'min'}. controls whether the chosen val metric should be
+                maximized or minimized, e.g. for "bbox/AP50" it should be "max"
+            file_prefix (str): the prefix of checkpoint's filename, defaults to "model_best"
+        """
+        self._logger = logging.getLogger(__name__)
+        self._period = eval_period
+        self._val_metric = val_metric
+        assert mode in [
+            "max",
+            "min",
+        ], f'Mode "{mode}" to `BestCheckpointer` is unknown. It should be one of {"max", "min"}.'
+        if mode == "max":
+            self._compare = operator.gt
+        else:
+            self._compare = operator.lt
+        self._checkpointer = checkpointer
+        self._file_prefix = file_prefix
+        self.best_metric = None
+        self.best_iter = None
+
+    def _update_best(self, val, iteration):
+        if math.isnan(val) or math.isinf(val):
+            return False
+        self.best_metric = val
+        self.best_iter = iteration
+        return True
+
+    def _best_checking(self):
+        metric_tuple = self.trainer.storage.latest().get(self._val_metric)
+        if metric_tuple is None:
+            self._logger.warning(
+                f"Given val metric {self._val_metric} does not seem to be computed/stored."
+                "Will not be checkpointing based on it."
+            )
+            return
+        else:
+            latest_metric, metric_iter = metric_tuple
+
+        if self.best_metric is None:
+            if self._update_best(latest_metric, metric_iter):
+                additional_state = {"iteration": metric_iter}
+                self._checkpointer.save(f"{self._file_prefix}", **additional_state)
+                self._logger.info(
+                    f"Saved first model at {self.best_metric:0.5f} @ {self.best_iter} steps"
+                )
+        elif self._compare(latest_metric, self.best_metric):
+            additional_state = {"iteration": metric_iter}
+            self._checkpointer.save(f"{self._file_prefix}", **additional_state)
+            self._logger.info(
+                f"Saved best model as latest eval score for {self._val_metric} is "
+                f"{latest_metric:0.5f}, better than last best score "
+                f"{self.best_metric:0.5f} @ iteration {self.best_iter}."
+            )
+            self._update_best(latest_metric, metric_iter)
+        else:
+            self._logger.info(
+                f"Not saving as latest eval score for {self._val_metric} is {latest_metric:0.5f}, "
+                f"not better than best score {self.best_metric:0.5f} @ iteration {self.best_iter}."
+            )
+
+    def after_step(self):
+        # same conditions as `EvalHook`
+        next_iter = self.trainer.iter + 1
+        if (
+            self._period > 0
+            and next_iter % self._period == 0
+            and next_iter != self.trainer.max_iter
+        ):
+            self._best_checking()
+
+    def after_train(self):
+        # same conditions as `EvalHook`
+        if self.trainer.iter + 1 >= self.trainer.max_iter:
+            self._best_checking()
+
+
+class LRScheduler(HookBase):
+    """
+    A hook which executes a torch builtin LR scheduler and summarizes the LR.
+    It is executed after every iteration.
+    """
+
+    def __init__(self, optimizer=None, scheduler=None):
+        """
+        Args:
+            optimizer (torch.optim.Optimizer):
+            scheduler (torch.optim.LRScheduler or fvcore.common.param_scheduler.ParamScheduler):
+                if a :class:`ParamScheduler` object, it defines the multiplier over the base LR
+                in the optimizer.
+
+        If any argument is not given, will try to obtain it from the trainer.
+        """
+        self._optimizer = optimizer
+        self._scheduler = scheduler
+
+    def before_train(self):
+        self._optimizer = self._optimizer or self.trainer.optimizer
+        if isinstance(self.scheduler, ParamScheduler):
+            self._scheduler = LRMultiplier(
+                self._optimizer,
+                self.scheduler,
+                self.trainer.max_iter,
+                last_iter=self.trainer.iter - 1,
+            )
+        self._best_param_group_id = LRScheduler.get_best_param_group_id(self._optimizer)
+
+    @staticmethod
+    def get_best_param_group_id(optimizer):
+        # NOTE: some heuristics on what LR to summarize
+        # summarize the param group with most parameters
+        largest_group = max(len(g["params"]) for g in optimizer.param_groups)
+
+        if largest_group == 1:
+            # If all groups have one parameter,
+            # then find the most common initial LR, and use it for summary
+            lr_count = Counter([g["lr"] for g in optimizer.param_groups])
+            lr = lr_count.most_common()[0][0]
+            for i, g in enumerate(optimizer.param_groups):
+                if g["lr"] == lr:
+                    return i
+        else:
+            for i, g in enumerate(optimizer.param_groups):
+                if len(g["params"]) == largest_group:
+                    return i
+
+    def after_step(self):
+        lr = self._optimizer.param_groups[self._best_param_group_id]["lr"]
+        self.trainer.storage.put_scalar("lr", lr, smoothing_hint=False)
+        self.scheduler.step()
+
+    @property
+    def scheduler(self):
+        return self._scheduler or self.trainer.scheduler
+
+    def state_dict(self):
+        if isinstance(self.scheduler, _LRScheduler):
+            return self.scheduler.state_dict()
+        return {}
+
+    def load_state_dict(self, state_dict):
+        if isinstance(self.scheduler, _LRScheduler):
+            logger = logging.getLogger(__name__)
+            logger.info("Loading scheduler from state_dict ...")
+            self.scheduler.load_state_dict(state_dict)
+
+
+class TorchProfiler(HookBase):
+    """
+    A hook which runs `torch.profiler.profile`.
+
+    Examples:
+    ::
+        hooks.TorchProfiler(
+             lambda trainer: 10 < trainer.iter < 20, self.cfg.OUTPUT_DIR
+        )
+
+    The above example will run the profiler for iteration 10~20 and dump
+    results to ``OUTPUT_DIR``. We did not profile the first few iterations
+    because they are typically slower than the rest.
+    The result files can be loaded in the ``chrome://tracing`` page in chrome browser,
+    and the tensorboard visualizations can be visualized using
+    ``tensorboard --logdir OUTPUT_DIR/log``
+    """
+
+    def __init__(self, enable_predicate, output_dir, *, activities=None, save_tensorboard=True):
+        """
+        Args:
+            enable_predicate (callable[trainer -> bool]): a function which takes a trainer,
+                and returns whether to enable the profiler.
+                It will be called once every step, and can be used to select which steps to profile.
+            output_dir (str): the output directory to dump tracing files.
+            activities (iterable): same as in `torch.profiler.profile`.
+            save_tensorboard (bool): whether to save tensorboard visualizations at (output_dir)/log/
+        """
+        self._enable_predicate = enable_predicate
+        self._activities = activities
+        self._output_dir = output_dir
+        self._save_tensorboard = save_tensorboard
+
+    def before_step(self):
+        if self._enable_predicate(self.trainer):
+            if self._save_tensorboard:
+                on_trace_ready = torch.profiler.tensorboard_trace_handler(
+                    os.path.join(
+                        self._output_dir,
+                        "log",
+                        "profiler-tensorboard-iter{}".format(self.trainer.iter),
+                    ),
+                    f"worker{comm.get_rank()}",
+                )
+            else:
+                on_trace_ready = None
+            self._profiler = torch.profiler.profile(
+                activities=self._activities,
+                on_trace_ready=on_trace_ready,
+                record_shapes=True,
+                profile_memory=True,
+                with_stack=True,
+                with_flops=True,
+            )
+            self._profiler.__enter__()
+        else:
+            self._profiler = None
+
+    def after_step(self):
+        if self._profiler is None:
+            return
+        self._profiler.__exit__(None, None, None)
+        if not self._save_tensorboard:
+            PathManager.mkdirs(self._output_dir)
+            out_file = os.path.join(
+                self._output_dir, "profiler-trace-iter{}.json".format(self.trainer.iter)
+            )
+            if "://" not in out_file:
+                self._profiler.export_chrome_trace(out_file)
+            else:
+                # Support non-posix filesystems
+                with tempfile.TemporaryDirectory(prefix="detectron2_profiler") as d:
+                    tmp_file = os.path.join(d, "tmp.json")
+                    self._profiler.export_chrome_trace(tmp_file)
+                    with open(tmp_file) as f:
+                        content = f.read()
+                with PathManager.open(out_file, "w") as f:
+                    f.write(content)
+
+
+class AutogradProfiler(TorchProfiler):
+    """
+    A hook which runs `torch.autograd.profiler.profile`.
+
+    Examples:
+    ::
+        hooks.AutogradProfiler(
+             lambda trainer: 10 < trainer.iter < 20, self.cfg.OUTPUT_DIR
+        )
+
+    The above example will run the profiler for iteration 10~20 and dump
+    results to ``OUTPUT_DIR``. We did not profile the first few iterations
+    because they are typically slower than the rest.
+    The result files can be loaded in the ``chrome://tracing`` page in chrome browser.
+
+    Note:
+        When used together with NCCL on older version of GPUs,
+        autograd profiler may cause deadlock because it unnecessarily allocates
+        memory on every device it sees. The memory management calls, if
+        interleaved with NCCL calls, lead to deadlock on GPUs that do not
+        support ``cudaLaunchCooperativeKernelMultiDevice``.
+    """
+
+    def __init__(self, enable_predicate, output_dir, *, use_cuda=True):
+        """
+        Args:
+            enable_predicate (callable[trainer -> bool]): a function which takes a trainer,
+                and returns whether to enable the profiler.
+                It will be called once every step, and can be used to select which steps to profile.
+            output_dir (str): the output directory to dump tracing files.
+            use_cuda (bool): same as in `torch.autograd.profiler.profile`.
+        """
+        warnings.warn("AutogradProfiler has been deprecated in favor of TorchProfiler.")
+        self._enable_predicate = enable_predicate
+        self._use_cuda = use_cuda
+        self._output_dir = output_dir
+
+    def before_step(self):
+        if self._enable_predicate(self.trainer):
+            self._profiler = torch.autograd.profiler.profile(use_cuda=self._use_cuda)
+            self._profiler.__enter__()
+        else:
+            self._profiler = None
+
+
+class EvalHook(HookBase):
+    """
+    Run an evaluation function periodically, and at the end of training.
+
+    It is executed every ``eval_period`` iterations and after the last iteration.
+    """
+
+    def __init__(self, eval_period, eval_function, eval_after_train=True):
+        """
+        Args:
+            eval_period (int): the period to run `eval_function`. Set to 0 to
+                not evaluate periodically (but still evaluate after the last iteration
+                if `eval_after_train` is True).
+            eval_function (callable): a function which takes no arguments, and
+                returns a nested dict of evaluation metrics.
+            eval_after_train (bool): whether to evaluate after the last iteration
+
+        Note:
+            This hook must be enabled in all or none workers.
+            If you would like only certain workers to perform evaluation,
+            give other workers a no-op function (`eval_function=lambda: None`).
+        """
+        self._period = eval_period
+        self._func = eval_function
+        self._eval_after_train = eval_after_train
+
+    def _do_eval(self):
+        results = self._func()
+
+        if results:
+            assert isinstance(
+                results, dict
+            ), "Eval function must return a dict. Got {} instead.".format(results)
+
+            flattened_results = flatten_results_dict(results)
+            for k, v in flattened_results.items():
+                try:
+                    v = float(v)
+                except Exception as e:
+                    raise ValueError(
+                        "[EvalHook] eval_function should return a nested dict of float. "
+                        "Got '{}: {}' instead.".format(k, v)
+                    ) from e
+            self.trainer.storage.put_scalars(**flattened_results, smoothing_hint=False)
+
+        # Evaluation may take different time among workers.
+        # A barrier make them start the next iteration together.
+        comm.synchronize()
+
+    def after_step(self):
+        next_iter = self.trainer.iter + 1
+        if self._period > 0 and next_iter % self._period == 0:
+            # do the last eval in after_train
+            if next_iter != self.trainer.max_iter:
+                self._do_eval()
+
+    def after_train(self):
+        # This condition is to prevent the eval from running after a failed training
+        if self._eval_after_train and self.trainer.iter + 1 >= self.trainer.max_iter:
+            self._do_eval()
+        # func is likely a closure that holds reference to the trainer
+        # therefore we clean it to avoid circular reference in the end
+        del self._func
+
+
+class PreciseBN(HookBase):
+    """
+    The standard implementation of BatchNorm uses EMA in inference, which is
+    sometimes suboptimal.
+    This class computes the true average of statistics rather than the moving average,
+    and put true averages to every BN layer in the given model.
+
+    It is executed every ``period`` iterations and after the last iteration.
+    """
+
+    def __init__(self, period, model, data_loader, num_iter):
+        """
+        Args:
+            period (int): the period this hook is run, or 0 to not run during training.
+                The hook will always run in the end of training.
+            model (nn.Module): a module whose all BN layers in training mode will be
+                updated by precise BN.
+                Note that user is responsible for ensuring the BN layers to be
+                updated are in training mode when this hook is triggered.
+            data_loader (iterable): it will produce data to be run by `model(data)`.
+            num_iter (int): number of iterations used to compute the precise
+                statistics.
+        """
+        self._logger = logging.getLogger(__name__)
+        if len(get_bn_modules(model)) == 0:
+            self._logger.info(
+                "PreciseBN is disabled because model does not contain BN layers in training mode."
+            )
+            self._disabled = True
+            return
+
+        self._model = model
+        self._data_loader = data_loader
+        self._num_iter = num_iter
+        self._period = period
+        self._disabled = False
+
+        self._data_iter = None
+
+    def after_step(self):
+        next_iter = self.trainer.iter + 1
+        is_final = next_iter == self.trainer.max_iter
+        if is_final or (self._period > 0 and next_iter % self._period == 0):
+            self.update_stats()
+
+    def update_stats(self):
+        """
+        Update the model with precise statistics. Users can manually call this method.
+        """
+        if self._disabled:
+            return
+
+        if self._data_iter is None:
+            self._data_iter = iter(self._data_loader)
+
+        def data_loader():
+            for num_iter in itertools.count(1):
+                if num_iter % 100 == 0:
+                    self._logger.info(
+                        "Running precise-BN ... {}/{} iterations.".format(num_iter, self._num_iter)
+                    )
+                # This way we can reuse the same iterator
+                yield next(self._data_iter)
+
+        with EventStorage():  # capture events in a new storage to discard them
+            self._logger.info(
+                "Running precise-BN for {} iterations...  ".format(self._num_iter)
+                + "Note that this could produce different statistics every time."
+            )
+            update_bn_stats(self._model, data_loader(), self._num_iter)
+
+
+class TorchMemoryStats(HookBase):
+    """
+    Writes pytorch's cuda memory statistics periodically.
+    """
+
+    def __init__(self, period=20, max_runs=10):
+        """
+        Args:
+            period (int): Output stats each 'period' iterations
+            max_runs (int): Stop the logging after 'max_runs'
+        """
+
+        self._logger = logging.getLogger(__name__)
+        self._period = period
+        self._max_runs = max_runs
+        self._runs = 0
+
+    def after_step(self):
+        if self._runs > self._max_runs:
+            return
+
+        if (self.trainer.iter + 1) % self._period == 0 or (
+            self.trainer.iter == self.trainer.max_iter - 1
+        ):
+            if torch.cuda.is_available():
+                max_reserved_mb = torch.cuda.max_memory_reserved() / 1024.0 / 1024.0
+                reserved_mb = torch.cuda.memory_reserved() / 1024.0 / 1024.0
+                max_allocated_mb = torch.cuda.max_memory_allocated() / 1024.0 / 1024.0
+                allocated_mb = torch.cuda.memory_allocated() / 1024.0 / 1024.0
+
+                self._logger.info(
+                    (
+                        " iter: {} "
+                        " max_reserved_mem: {:.0f}MB "
+                        " reserved_mem: {:.0f}MB "
+                        " max_allocated_mem: {:.0f}MB "
+                        " allocated_mem: {:.0f}MB "
+                    ).format(
+                        self.trainer.iter,
+                        max_reserved_mb,
+                        reserved_mb,
+                        max_allocated_mb,
+                        allocated_mb,
+                    )
+                )
+
+                self._runs += 1
+                if self._runs == self._max_runs:
+                    mem_summary = torch.cuda.memory_summary()
+                    self._logger.info("\n" + mem_summary)
+
+                torch.cuda.reset_peak_memory_stats()

detectron2/engine/launch.py

@@ -0,0 +1,123 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import logging
+from datetime import timedelta
+import torch
+import torch.distributed as dist
+import torch.multiprocessing as mp
+
+from detectron2.utils import comm
+
+__all__ = ["DEFAULT_TIMEOUT", "launch"]
+
+DEFAULT_TIMEOUT = timedelta(minutes=30)
+
+
+def _find_free_port():
+    import socket
+
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    # Binding to port 0 will cause the OS to find an available port for us
+    sock.bind(("", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    # NOTE: there is still a chance the port could be taken by other processes.
+    return port
+
+
+def launch(
+    main_func,
+    # Should be num_processes_per_machine, but kept for compatibility.
+    num_gpus_per_machine,
+    num_machines=1,
+    machine_rank=0,
+    dist_url=None,
+    args=(),
+    timeout=DEFAULT_TIMEOUT,
+):
+    """
+    Launch multi-process or distributed training.
+    This function must be called on all machines involved in the training.
+    It will spawn child processes (defined by ``num_gpus_per_machine``) on each machine.
+
+    Args:
+        main_func: a function that will be called by `main_func(*args)`
+        num_gpus_per_machine (int): number of processes per machine. When
+            using GPUs, this should be the number of GPUs.
+        num_machines (int): the total number of machines
+        machine_rank (int): the rank of this machine
+        dist_url (str): url to connect to for distributed jobs, including protocol
+                       e.g. "tcp://127.0.0.1:8686".
+                       Can be set to "auto" to automatically select a free port on localhost
+        timeout (timedelta): timeout of the distributed workers
+        args (tuple): arguments passed to main_func
+    """
+    world_size = num_machines * num_gpus_per_machine
+    if world_size > 1:
+        # https://github.com/pytorch/pytorch/pull/14391
+        # TODO prctl in spawned processes
+
+        if dist_url == "auto":
+            assert num_machines == 1, "dist_url=auto not supported in multi-machine jobs."
+            port = _find_free_port()
+            dist_url = f"tcp://127.0.0.1:{port}"
+        if num_machines > 1 and dist_url.startswith("file://"):
+            logger = logging.getLogger(__name__)
+            logger.warning(
+                "file:// is not a reliable init_method in multi-machine jobs. Prefer tcp://"
+            )
+
+        mp.start_processes(
+            _distributed_worker,
+            nprocs=num_gpus_per_machine,
+            args=(
+                main_func,
+                world_size,
+                num_gpus_per_machine,
+                machine_rank,
+                dist_url,
+                args,
+                timeout,
+            ),
+            daemon=False,
+        )
+    else:
+        main_func(*args)
+
+
+def _distributed_worker(
+    local_rank,
+    main_func,
+    world_size,
+    num_gpus_per_machine,
+    machine_rank,
+    dist_url,
+    args,
+    timeout=DEFAULT_TIMEOUT,
+):
+    has_gpu = torch.cuda.is_available()
+    if has_gpu:
+        assert num_gpus_per_machine <= torch.cuda.device_count()
+    global_rank = machine_rank * num_gpus_per_machine + local_rank
+    try:
+        dist.init_process_group(
+            backend="NCCL" if has_gpu else "GLOO",
+            init_method=dist_url,
+            world_size=world_size,
+            rank=global_rank,
+            timeout=timeout,
+        )
+    except Exception as e:
+        logger = logging.getLogger(__name__)
+        logger.error("Process group URL: {}".format(dist_url))
+        raise e
+
+    # Setup the local process group.
+    comm.create_local_process_group(num_gpus_per_machine)
+    if has_gpu:
+        torch.cuda.set_device(local_rank)
+
+    # synchronize is needed here to prevent a possible timeout after calling init_process_group
+    # See: https://github.com/facebookresearch/maskrcnn-benchmark/issues/172
+    comm.synchronize()
+
+    main_func(*args)

detectron2/engine/train_loop.py

@@ -0,0 +1,530 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) Facebook, Inc. and its affiliates.
+import concurrent.futures
+import logging
+import numpy as np
+import time
+import weakref
+from typing import List, Mapping, Optional
+import torch
+from torch.nn.parallel import DataParallel, DistributedDataParallel
+
+import detectron2.utils.comm as comm
+from detectron2.utils.events import EventStorage, get_event_storage
+from detectron2.utils.logger import _log_api_usage
+
+__all__ = ["HookBase", "TrainerBase", "SimpleTrainer", "AMPTrainer"]
+
+
+class HookBase:
+    """
+    Base class for hooks that can be registered with :class:`TrainerBase`.
+
+    Each hook can implement 4 methods. The way they are called is demonstrated
+    in the following snippet:
+    ::
+        hook.before_train()
+        for iter in range(start_iter, max_iter):
+            hook.before_step()
+            trainer.run_step()
+            hook.after_step()
+        iter += 1
+        hook.after_train()
+
+    Notes:
+        1. In the hook method, users can access ``self.trainer`` to access more
+           properties about the context (e.g., model, current iteration, or config
+           if using :class:`DefaultTrainer`).
+
+        2. A hook that does something in :meth:`before_step` can often be
+           implemented equivalently in :meth:`after_step`.
+           If the hook takes non-trivial time, it is strongly recommended to
+           implement the hook in :meth:`after_step` instead of :meth:`before_step`.
+           The convention is that :meth:`before_step` should only take negligible time.
+
+           Following this convention will allow hooks that do care about the difference
+           between :meth:`before_step` and :meth:`after_step` (e.g., timer) to
+           function properly.
+
+    """
+
+    trainer: "TrainerBase" = None
+    """
+    A weak reference to the trainer object. Set by the trainer when the hook is registered.
+    """
+
+    def before_train(self):
+        """
+        Called before the first iteration.
+        """
+        pass
+
+    def after_train(self):
+        """
+        Called after the last iteration.
+        """
+        pass
+
+    def before_step(self):
+        """
+        Called before each iteration.
+        """
+        pass
+
+    def after_backward(self):
+        """
+        Called after the backward pass of each iteration.
+        """
+        pass
+
+    def after_step(self):
+        """
+        Called after each iteration.
+        """
+        pass
+
+    def state_dict(self):
+        """
+        Hooks are stateless by default, but can be made checkpointable by
+        implementing `state_dict` and `load_state_dict`.
+        """
+        return {}
+
+
+class TrainerBase:
+    """
+    Base class for iterative trainer with hooks.
+
+    The only assumption we made here is: the training runs in a loop.
+    A subclass can implement what the loop is.
+    We made no assumptions about the existence of dataloader, optimizer, model, etc.
+
+    Attributes:
+        iter(int): the current iteration.
+
+        start_iter(int): The iteration to start with.
+            By convention the minimum possible value is 0.
+
+        max_iter(int): The iteration to end training.
+
+        storage(EventStorage): An EventStorage that's opened during the course of training.
+    """
+
+    def __init__(self) -> None:
+        self._hooks: List[HookBase] = []
+        self.iter: int = 0
+        self.start_iter: int = 0
+        self.max_iter: int
+        self.storage: EventStorage
+        _log_api_usage("trainer." + self.__class__.__name__)
+
+    def register_hooks(self, hooks: List[Optional[HookBase]]) -> None:
+        """
+        Register hooks to the trainer. The hooks are executed in the order
+        they are registered.
+
+        Args:
+            hooks (list[Optional[HookBase]]): list of hooks
+        """
+        hooks = [h for h in hooks if h is not None]
+        for h in hooks:
+            assert isinstance(h, HookBase)
+            # To avoid circular reference, hooks and trainer cannot own each other.
+            # This normally does not matter, but will cause memory leak if the
+            # involved objects contain __del__:
+            # See http://engineering.hearsaysocial.com/2013/06/16/circular-references-in-python/
+            h.trainer = weakref.proxy(self)
+        self._hooks.extend(hooks)
+
+    def train(self, start_iter: int, max_iter: int):
+        """
+        Args:
+            start_iter, max_iter (int): See docs above
+        """
+        logger = logging.getLogger(__name__)
+        logger.info("Starting training from iteration {}".format(start_iter))
+
+        self.iter = self.start_iter = start_iter
+        self.max_iter = max_iter
+
+        with EventStorage(start_iter) as self.storage:
+            try:
+                self.before_train()
+                for self.iter in range(start_iter, max_iter):
+                    self.before_step()
+                    self.run_step()
+                    self.after_step()
+                # self.iter == max_iter can be used by `after_train` to
+                # tell whether the training successfully finished or failed
+                # due to exceptions.
+                self.iter += 1
+            except Exception:
+                logger.exception("Exception during training:")
+                raise
+            finally:
+                self.after_train()
+
+    def before_train(self):
+        for h in self._hooks:
+            h.before_train()
+
+    def after_train(self):
+        self.storage.iter = self.iter
+        for h in self._hooks:
+            h.after_train()
+
+    def before_step(self):
+        # Maintain the invariant that storage.iter == trainer.iter
+        # for the entire execution of each step
+        self.storage.iter = self.iter
+
+        for h in self._hooks:
+            h.before_step()
+
+    def after_backward(self):
+        for h in self._hooks:
+            h.after_backward()
+
+    def after_step(self):
+        for h in self._hooks:
+            h.after_step()
+
+    def run_step(self):
+        raise NotImplementedError
+
+    def state_dict(self):
+        ret = {"iteration": self.iter}
+        hooks_state = {}
+        for h in self._hooks:
+            sd = h.state_dict()
+            if sd:
+                name = type(h).__qualname__
+                if name in hooks_state:
+                    # TODO handle repetitive stateful hooks
+                    continue
+                hooks_state[name] = sd
+        if hooks_state:
+            ret["hooks"] = hooks_state
+        return ret
+
+    def load_state_dict(self, state_dict):
+        logger = logging.getLogger(__name__)
+        self.iter = state_dict["iteration"]
+        for key, value in state_dict.get("hooks", {}).items():
+            for h in self._hooks:
+                try:
+                    name = type(h).__qualname__
+                except AttributeError:
+                    continue
+                if name == key:
+                    h.load_state_dict(value)
+                    break
+            else:
+                logger.warning(f"Cannot find the hook '{key}', its state_dict is ignored.")
+
+
+class SimpleTrainer(TrainerBase):
+    """
+    A simple trainer for the most common type of task:
+    single-cost single-optimizer single-data-source iterative optimization,
+    optionally using data-parallelism.
+    It assumes that every step, you:
+
+    1. Compute the loss with a data from the data_loader.
+    2. Compute the gradients with the above loss.
+    3. Update the model with the optimizer.
+
+    All other tasks during training (checkpointing, logging, evaluation, LR schedule)
+    are maintained by hooks, which can be registered by :meth:`TrainerBase.register_hooks`.
+
+    If you want to do anything fancier than this,
+    either subclass TrainerBase and implement your own `run_step`,
+    or write your own training loop.
+    """
+
+    def __init__(
+        self,
+        model,
+        data_loader,
+        optimizer,
+        gather_metric_period=1,
+        zero_grad_before_forward=False,
+        async_write_metrics=False,
+    ):
+        """
+        Args:
+            model: a torch Module. Takes a data from data_loader and returns a
+                dict of losses.
+            data_loader: an iterable. Contains data to be used to call model.
+            optimizer: a torch optimizer.
+            gather_metric_period: an int. Every gather_metric_period iterations
+                the metrics are gathered from all the ranks to rank 0 and logged.
+            zero_grad_before_forward: whether to zero the gradients before the forward.
+            async_write_metrics: bool. If True, then write metrics asynchronously to improve
+                training speed
+        """
+        super().__init__()
+
+        """
+        We set the model to training mode in the trainer.
+        However it's valid to train a model that's in eval mode.
+        If you want your model (or a submodule of it) to behave
+        like evaluation during training, you can overwrite its train() method.
+        """
+        model.train()
+
+        self.model = model
+        self.data_loader = data_loader
+        # to access the data loader iterator, call `self._data_loader_iter`
+        self._data_loader_iter_obj = None
+        self.optimizer = optimizer
+        self.gather_metric_period = gather_metric_period
+        self.zero_grad_before_forward = zero_grad_before_forward
+        self.async_write_metrics = async_write_metrics
+        # create a thread pool that can execute non critical logic in run_step asynchronically
+        # use only 1 worker so tasks will be executred in order of submitting.
+        self.concurrent_executor = concurrent.futures.ThreadPoolExecutor(max_workers=1)
+
+    def run_step(self):
+        """
+        Implement the standard training logic described above.
+        """
+        assert self.model.training, "[SimpleTrainer] model was changed to eval mode!"
+        start = time.perf_counter()
+        """
+        If you want to do something with the data, you can wrap the dataloader.
+        """
+        data = next(self._data_loader_iter)
+        data_time = time.perf_counter() - start
+
+        if self.zero_grad_before_forward:
+            """
+            If you need to accumulate gradients or do something similar, you can
+            wrap the optimizer with your custom `zero_grad()` method.
+            """
+            self.optimizer.zero_grad()
+
+        """
+        If you want to do something with the losses, you can wrap the model.
+        """
+        loss_dict = self.model(data)
+        if isinstance(loss_dict, torch.Tensor):
+            losses = loss_dict
+            loss_dict = {"total_loss": loss_dict}
+        else:
+            losses = sum(loss_dict.values())
+        if not self.zero_grad_before_forward:
+            """
+            If you need to accumulate gradients or do something similar, you can
+            wrap the optimizer with your custom `zero_grad()` method.
+            """
+            self.optimizer.zero_grad()
+        losses.backward()
+
+        self.after_backward()
+
+        if self.async_write_metrics:
+            # write metrics asynchronically
+            self.concurrent_executor.submit(
+                self._write_metrics, loss_dict, data_time, iter=self.iter
+            )
+        else:
+            self._write_metrics(loss_dict, data_time)
+
+        """
+        If you need gradient clipping/scaling or other processing, you can
+        wrap the optimizer with your custom `step()` method. But it is
+        suboptimal as explained in https://arxiv.org/abs/2006.15704 Sec 3.2.4
+        """
+        self.optimizer.step()
+
+    @property
+    def _data_loader_iter(self):
+        # only create the data loader iterator when it is used
+        if self._data_loader_iter_obj is None:
+            self._data_loader_iter_obj = iter(self.data_loader)
+        return self._data_loader_iter_obj
+
+    def reset_data_loader(self, data_loader_builder):
+        """
+        Delete and replace the current data loader with a new one, which will be created
+        by calling `data_loader_builder` (without argument).
+        """
+        del self.data_loader
+        data_loader = data_loader_builder()
+        self.data_loader = data_loader
+        self._data_loader_iter_obj = None
+
+    def _write_metrics(
+        self,
+        loss_dict: Mapping[str, torch.Tensor],
+        data_time: float,
+        prefix: str = "",
+        iter: Optional[int] = None,
+    ) -> None:
+        logger = logging.getLogger(__name__)
+
+        iter = self.iter if iter is None else iter
+        if (iter + 1) % self.gather_metric_period == 0:
+            try:
+                SimpleTrainer.write_metrics(loss_dict, data_time, iter, prefix)
+            except Exception:
+                logger.exception("Exception in writing metrics: ")
+                raise
+
+    @staticmethod
+    def write_metrics(
+        loss_dict: Mapping[str, torch.Tensor],
+        data_time: float,
+        cur_iter: int,
+        prefix: str = "",
+    ) -> None:
+        """
+        Args:
+            loss_dict (dict): dict of scalar losses
+            data_time (float): time taken by the dataloader iteration
+            prefix (str): prefix for logging keys
+        """
+        metrics_dict = {k: v.detach().cpu().item() for k, v in loss_dict.items()}
+        metrics_dict["data_time"] = data_time
+
+        storage = get_event_storage()
+        # Keep track of data time per rank
+        storage.put_scalar("rank_data_time", data_time, cur_iter=cur_iter)
+
+        # Gather metrics among all workers for logging
+        # This assumes we do DDP-style training, which is currently the only
+        # supported method in detectron2.
+        all_metrics_dict = comm.gather(metrics_dict)
+
+        if comm.is_main_process():
+            # data_time among workers can have high variance. The actual latency
+            # caused by data_time is the maximum among workers.
+            data_time = np.max([x.pop("data_time") for x in all_metrics_dict])
+            storage.put_scalar("data_time", data_time, cur_iter=cur_iter)
+
+            # average the rest metrics
+            metrics_dict = {
+                k: np.mean([x[k] for x in all_metrics_dict]) for k in all_metrics_dict[0].keys()
+            }
+            total_losses_reduced = sum(metrics_dict.values())
+            if not np.isfinite(total_losses_reduced):
+                raise FloatingPointError(
+                    f"Loss became infinite or NaN at iteration={cur_iter}!\n"
+                    f"loss_dict = {metrics_dict}"
+                )
+
+            storage.put_scalar(
+                "{}total_loss".format(prefix), total_losses_reduced, cur_iter=cur_iter
+            )
+            if len(metrics_dict) > 1:
+                storage.put_scalars(cur_iter=cur_iter, **metrics_dict)
+
+    def state_dict(self):
+        ret = super().state_dict()
+        ret["optimizer"] = self.optimizer.state_dict()
+        return ret
+
+    def load_state_dict(self, state_dict):
+        super().load_state_dict(state_dict)
+        self.optimizer.load_state_dict(state_dict["optimizer"])
+
+    def after_train(self):
+        super().after_train()
+        self.concurrent_executor.shutdown(wait=True)
+
+
+class AMPTrainer(SimpleTrainer):
+    """
+    Like :class:`SimpleTrainer`, but uses PyTorch's native automatic mixed precision
+    in the training loop.
+    """
+
+    def __init__(
+        self,
+        model,
+        data_loader,
+        optimizer,
+        gather_metric_period=1,
+        zero_grad_before_forward=False,
+        grad_scaler=None,
+        precision: torch.dtype = torch.float16,
+        log_grad_scaler: bool = False,
+        async_write_metrics=False,
+    ):
+        """
+        Args:
+            model, data_loader, optimizer, gather_metric_period, zero_grad_before_forward,
+                async_write_metrics: same as in :class:`SimpleTrainer`.
+            grad_scaler: torch GradScaler to automatically scale gradients.
+            precision: torch.dtype as the target precision to cast to in computations
+        """
+        unsupported = "AMPTrainer does not support single-process multi-device training!"
+        if isinstance(model, DistributedDataParallel):
+            assert not (model.device_ids and len(model.device_ids) > 1), unsupported
+        assert not isinstance(model, DataParallel), unsupported
+
+        super().__init__(
+            model, data_loader, optimizer, gather_metric_period, zero_grad_before_forward
+        )
+
+        if grad_scaler is None:
+            from torch.cuda.amp import GradScaler
+
+            grad_scaler = GradScaler()
+        self.grad_scaler = grad_scaler
+        self.precision = precision
+        self.log_grad_scaler = log_grad_scaler
+
+    def run_step(self):
+        """
+        Implement the AMP training logic.
+        """
+        assert self.model.training, "[AMPTrainer] model was changed to eval mode!"
+        assert torch.cuda.is_available(), "[AMPTrainer] CUDA is required for AMP training!"
+        from torch.cuda.amp import autocast
+
+        start = time.perf_counter()
+        data = next(self._data_loader_iter)
+        data_time = time.perf_counter() - start
+
+        if self.zero_grad_before_forward:
+            self.optimizer.zero_grad()
+        with autocast(dtype=self.precision):
+            loss_dict = self.model(data)
+            if isinstance(loss_dict, torch.Tensor):
+                losses = loss_dict
+                loss_dict = {"total_loss": loss_dict}
+            else:
+                losses = sum(loss_dict.values())
+
+        if not self.zero_grad_before_forward:
+            self.optimizer.zero_grad()
+
+        self.grad_scaler.scale(losses).backward()
+
+        if self.log_grad_scaler:
+            storage = get_event_storage()
+            storage.put_scalar("[metric]grad_scaler", self.grad_scaler.get_scale())
+
+        self.after_backward()
+
+        if self.async_write_metrics:
+            # write metrics asynchronically
+            self.concurrent_executor.submit(
+                self._write_metrics, loss_dict, data_time, iter=self.iter
+            )
+        else:
+            self._write_metrics(loss_dict, data_time)
+
+        self.grad_scaler.step(self.optimizer)
+        self.grad_scaler.update()
+
+    def state_dict(self):
+        ret = super().state_dict()
+        ret["grad_scaler"] = self.grad_scaler.state_dict()
+        return ret
+
+    def load_state_dict(self, state_dict):
+        super().load_state_dict(state_dict)
+        self.grad_scaler.load_state_dict(state_dict["grad_scaler"])

detectron2/evaluation/__init__.py

@@ -0,0 +1,12 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+from .cityscapes_evaluation import CityscapesInstanceEvaluator, CityscapesSemSegEvaluator
+from .coco_evaluation import COCOEvaluator
+from .rotated_coco_evaluation import RotatedCOCOEvaluator
+from .evaluator import DatasetEvaluator, DatasetEvaluators, inference_context, inference_on_dataset
+from .lvis_evaluation import LVISEvaluator
+from .panoptic_evaluation import COCOPanopticEvaluator
+from .pascal_voc_evaluation import PascalVOCDetectionEvaluator
+from .sem_seg_evaluation import SemSegEvaluator
+from .testing import print_csv_format, verify_results
+
+__all__ = [k for k in globals().keys() if not k.startswith("_")]

detectron2/evaluation/cityscapes_evaluation.py

@@ -0,0 +1,197 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import glob
+import logging
+import numpy as np
+import os
+import tempfile
+from collections import OrderedDict
+import torch
+from PIL import Image
+
+from detectron2.data import MetadataCatalog
+from detectron2.utils import comm
+from detectron2.utils.file_io import PathManager
+
+from .evaluator import DatasetEvaluator
+
+
+class CityscapesEvaluator(DatasetEvaluator):
+    """
+    Base class for evaluation using cityscapes API.
+    """
+
+    def __init__(self, dataset_name):
+        """
+        Args:
+            dataset_name (str): the name of the dataset.
+                It must have the following metadata associated with it:
+                "thing_classes", "gt_dir".
+        """
+        self._metadata = MetadataCatalog.get(dataset_name)
+        self._cpu_device = torch.device("cpu")
+        self._logger = logging.getLogger(__name__)
+
+    def reset(self):
+        self._working_dir = tempfile.TemporaryDirectory(prefix="cityscapes_eval_")
+        self._temp_dir = self._working_dir.name
+        # All workers will write to the same results directory
+        # TODO this does not work in distributed training
+        assert (
+            comm.get_local_size() == comm.get_world_size()
+        ), "CityscapesEvaluator currently do not work with multiple machines."
+        self._temp_dir = comm.all_gather(self._temp_dir)[0]
+        if self._temp_dir != self._working_dir.name:
+            self._working_dir.cleanup()
+        self._logger.info(
+            "Writing cityscapes results to temporary directory {} ...".format(self._temp_dir)
+        )
+
+
+class CityscapesInstanceEvaluator(CityscapesEvaluator):
+    """
+    Evaluate instance segmentation results on cityscapes dataset using cityscapes API.
+
+    Note:
+        * It does not work in multi-machine distributed training.
+        * It contains a synchronization, therefore has to be used on all ranks.
+        * Only the main process runs evaluation.
+    """
+
+    def process(self, inputs, outputs):
+        from cityscapesscripts.helpers.labels import name2label
+
+        for input, output in zip(inputs, outputs):
+            file_name = input["file_name"]
+            basename = os.path.splitext(os.path.basename(file_name))[0]
+            pred_txt = os.path.join(self._temp_dir, basename + "_pred.txt")
+
+            if "instances" in output:
+                output = output["instances"].to(self._cpu_device)
+                num_instances = len(output)
+                with open(pred_txt, "w") as fout:
+                    for i in range(num_instances):
+                        pred_class = output.pred_classes[i]
+                        classes = self._metadata.thing_classes[pred_class]
+                        class_id = name2label[classes].id
+                        score = output.scores[i]
+                        mask = output.pred_masks[i].numpy().astype("uint8")
+                        png_filename = os.path.join(
+                            self._temp_dir, basename + "_{}_{}.png".format(i, classes)
+                        )
+
+                        Image.fromarray(mask * 255).save(png_filename)
+                        fout.write(
+                            "{} {} {}\n".format(os.path.basename(png_filename), class_id, score)
+                        )
+            else:
+                # Cityscapes requires a prediction file for every ground truth image.
+                with open(pred_txt, "w") as fout:
+                    pass
+
+    def evaluate(self):
+        """
+        Returns:
+            dict: has a key "segm", whose value is a dict of "AP" and "AP50".
+        """
+        comm.synchronize()
+        if comm.get_rank() > 0:
+            return
+        import cityscapesscripts.evaluation.evalInstanceLevelSemanticLabeling as cityscapes_eval
+
+        self._logger.info("Evaluating results under {} ...".format(self._temp_dir))
+
+        # set some global states in cityscapes evaluation API, before evaluating
+        cityscapes_eval.args.predictionPath = os.path.abspath(self._temp_dir)
+        cityscapes_eval.args.predictionWalk = None
+        cityscapes_eval.args.JSONOutput = False
+        cityscapes_eval.args.colorized = False
+        cityscapes_eval.args.gtInstancesFile = os.path.join(self._temp_dir, "gtInstances.json")
+
+        # These lines are adopted from
+        # https://github.com/mcordts/cityscapesScripts/blob/master/cityscapesscripts/evaluation/evalInstanceLevelSemanticLabeling.py # noqa
+        gt_dir = PathManager.get_local_path(self._metadata.gt_dir)
+        groundTruthImgList = glob.glob(os.path.join(gt_dir, "*", "*_gtFine_instanceIds.png"))
+        assert len(
+            groundTruthImgList
+        ), "Cannot find any ground truth images to use for evaluation. Searched for: {}".format(
+            cityscapes_eval.args.groundTruthSearch
+        )
+        predictionImgList = []
+        for gt in groundTruthImgList:
+            predictionImgList.append(cityscapes_eval.getPrediction(gt, cityscapes_eval.args))
+        results = cityscapes_eval.evaluateImgLists(
+            predictionImgList, groundTruthImgList, cityscapes_eval.args
+        )["averages"]
+
+        ret = OrderedDict()
+        ret["segm"] = {"AP": results["allAp"] * 100, "AP50": results["allAp50%"] * 100}
+        self._working_dir.cleanup()
+        return ret
+
+
+class CityscapesSemSegEvaluator(CityscapesEvaluator):
+    """
+    Evaluate semantic segmentation results on cityscapes dataset using cityscapes API.
+
+    Note:
+        * It does not work in multi-machine distributed training.
+        * It contains a synchronization, therefore has to be used on all ranks.
+        * Only the main process runs evaluation.
+    """
+
+    def process(self, inputs, outputs):
+        from cityscapesscripts.helpers.labels import trainId2label
+
+        for input, output in zip(inputs, outputs):
+            file_name = input["file_name"]
+            basename = os.path.splitext(os.path.basename(file_name))[0]
+            pred_filename = os.path.join(self._temp_dir, basename + "_pred.png")
+
+            output = output["sem_seg"].argmax(dim=0).to(self._cpu_device).numpy()
+            pred = 255 * np.ones(output.shape, dtype=np.uint8)
+            for train_id, label in trainId2label.items():
+                if label.ignoreInEval:
+                    continue
+                pred[output == train_id] = label.id
+            Image.fromarray(pred).save(pred_filename)
+
+    def evaluate(self):
+        comm.synchronize()
+        if comm.get_rank() > 0:
+            return
+        # Load the Cityscapes eval script *after* setting the required env var,
+        # since the script reads CITYSCAPES_DATASET into global variables at load time.
+        import cityscapesscripts.evaluation.evalPixelLevelSemanticLabeling as cityscapes_eval
+
+        self._logger.info("Evaluating results under {} ...".format(self._temp_dir))
+
+        # set some global states in cityscapes evaluation API, before evaluating
+        cityscapes_eval.args.predictionPath = os.path.abspath(self._temp_dir)
+        cityscapes_eval.args.predictionWalk = None
+        cityscapes_eval.args.JSONOutput = False
+        cityscapes_eval.args.colorized = False
+
+        # These lines are adopted from
+        # https://github.com/mcordts/cityscapesScripts/blob/master/cityscapesscripts/evaluation/evalPixelLevelSemanticLabeling.py # noqa
+        gt_dir = PathManager.get_local_path(self._metadata.gt_dir)
+        groundTruthImgList = glob.glob(os.path.join(gt_dir, "*", "*_gtFine_labelIds.png"))
+        assert len(
+            groundTruthImgList
+        ), "Cannot find any ground truth images to use for evaluation. Searched for: {}".format(
+            cityscapes_eval.args.groundTruthSearch
+        )
+        predictionImgList = []
+        for gt in groundTruthImgList:
+            predictionImgList.append(cityscapes_eval.getPrediction(cityscapes_eval.args, gt))
+        results = cityscapes_eval.evaluateImgLists(
+            predictionImgList, groundTruthImgList, cityscapes_eval.args
+        )
+        ret = OrderedDict()
+        ret["sem_seg"] = {
+            "IoU": 100.0 * results["averageScoreClasses"],
+            "iIoU": 100.0 * results["averageScoreInstClasses"],
+            "IoU_sup": 100.0 * results["averageScoreCategories"],
+            "iIoU_sup": 100.0 * results["averageScoreInstCategories"],
+        }
+        self._working_dir.cleanup()
+        return ret

detectron2/evaluation/coco_evaluation.py

@@ -0,0 +1,722 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import contextlib
+import copy
+import io
+import itertools
+import json
+import logging
+import numpy as np
+import os
+import pickle
+from collections import OrderedDict
+import pycocotools.mask as mask_util
+import torch
+from pycocotools.coco import COCO
+from pycocotools.cocoeval import COCOeval
+from tabulate import tabulate
+
+import detectron2.utils.comm as comm
+from detectron2.config import CfgNode
+from detectron2.data import MetadataCatalog
+from detectron2.data.datasets.coco import convert_to_coco_json
+from detectron2.structures import Boxes, BoxMode, pairwise_iou
+from detectron2.utils.file_io import PathManager
+from detectron2.utils.logger import create_small_table
+
+from .evaluator import DatasetEvaluator
+
+try:
+    from detectron2.evaluation.fast_eval_api import COCOeval_opt
+except ImportError:
+    COCOeval_opt = COCOeval
+
+
+class COCOEvaluator(DatasetEvaluator):
+    """
+    Evaluate AR for object proposals, AP for instance detection/segmentation, AP
+    for keypoint detection outputs using COCO's metrics.
+    See http://cocodataset.org/#detection-eval and
+    http://cocodataset.org/#keypoints-eval to understand its metrics.
+    The metrics range from 0 to 100 (instead of 0 to 1), where a -1 or NaN means
+    the metric cannot be computed (e.g. due to no predictions made).
+
+    In addition to COCO, this evaluator is able to support any bounding box detection,
+    instance segmentation, or keypoint detection dataset.
+    """
+
+    def __init__(
+        self,
+        dataset_name,
+        tasks=None,
+        distributed=True,
+        output_dir=None,
+        *,
+        max_dets_per_image=None,
+        use_fast_impl=True,
+        kpt_oks_sigmas=(),
+        allow_cached_coco=True,
+    ):
+        """
+        Args:
+            dataset_name (str): name of the dataset to be evaluated.
+                It must have either the following corresponding metadata:
+
+                    "json_file": the path to the COCO format annotation
+
+                Or it must be in detectron2's standard dataset format
+                so it can be converted to COCO format automatically.
+            tasks (tuple[str]): tasks that can be evaluated under the given
+                configuration. A task is one of "bbox", "segm", "keypoints".
+                By default, will infer this automatically from predictions.
+            distributed (True): if True, will collect results from all ranks and run evaluation
+                in the main process.
+                Otherwise, will only evaluate the results in the current process.
+            output_dir (str): optional, an output directory to dump all
+                results predicted on the dataset. The dump contains two files:
+
+                1. "instances_predictions.pth" a file that can be loaded with `torch.load` and
+                   contains all the results in the format they are produced by the model.
+                2. "coco_instances_results.json" a json file in COCO's result format.
+            max_dets_per_image (int): limit on the maximum number of detections per image.
+                By default in COCO, this limit is to 100, but this can be customized
+                to be greater, as is needed in evaluation metrics AP fixed and AP pool
+                (see https://arxiv.org/pdf/2102.01066.pdf)
+                This doesn't affect keypoint evaluation.
+            use_fast_impl (bool): use a fast but **unofficial** implementation to compute AP.
+                Although the results should be very close to the official implementation in COCO
+                API, it is still recommended to compute results with the official API for use in
+                papers. The faster implementation also uses more RAM.
+            kpt_oks_sigmas (list[float]): The sigmas used to calculate keypoint OKS.
+                See http://cocodataset.org/#keypoints-eval
+                When empty, it will use the defaults in COCO.
+                Otherwise it should be the same length as ROI_KEYPOINT_HEAD.NUM_KEYPOINTS.
+            allow_cached_coco (bool): Whether to use cached coco json from previous validation
+                runs. You should set this to False if you need to use different validation data.
+                Defaults to True.
+        """
+        self._logger = logging.getLogger(__name__)
+        self._distributed = distributed
+        self._output_dir = output_dir
+
+        if use_fast_impl and (COCOeval_opt is COCOeval):
+            self._logger.info("Fast COCO eval is not built. Falling back to official COCO eval.")
+            use_fast_impl = False
+        self._use_fast_impl = use_fast_impl
+
+        # COCOeval requires the limit on the number of detections per image (maxDets) to be a list
+        # with at least 3 elements. The default maxDets in COCOeval is [1, 10, 100], in which the
+        # 3rd element (100) is used as the limit on the number of detections per image when
+        # evaluating AP. COCOEvaluator expects an integer for max_dets_per_image, so for COCOeval,
+        # we reformat max_dets_per_image into [1, 10, max_dets_per_image], based on the defaults.
+        if max_dets_per_image is None:
+            max_dets_per_image = [1, 10, 100]
+        else:
+            max_dets_per_image = [1, 10, max_dets_per_image]
+        self._max_dets_per_image = max_dets_per_image
+
+        if tasks is not None and isinstance(tasks, CfgNode):
+            kpt_oks_sigmas = (
+                tasks.TEST.KEYPOINT_OKS_SIGMAS if not kpt_oks_sigmas else kpt_oks_sigmas
+            )
+            self._logger.warn(
+                "COCO Evaluator instantiated using config, this is deprecated behavior."
+                " Please pass in explicit arguments instead."
+            )
+            self._tasks = None  # Infering it from predictions should be better
+        else:
+            self._tasks = tasks
+
+        self._cpu_device = torch.device("cpu")
+
+        self._metadata = MetadataCatalog.get(dataset_name)
+        if not hasattr(self._metadata, "json_file"):
+            if output_dir is None:
+                raise ValueError(
+                    "output_dir must be provided to COCOEvaluator "
+                    "for datasets not in COCO format."
+                )
+            self._logger.info(f"Trying to convert '{dataset_name}' to COCO format ...")
+
+            cache_path = os.path.join(output_dir, f"{dataset_name}_coco_format.json")
+            self._metadata.json_file = cache_path
+            convert_to_coco_json(dataset_name, cache_path, allow_cached=allow_cached_coco)
+
+        json_file = PathManager.get_local_path(self._metadata.json_file)
+        with contextlib.redirect_stdout(io.StringIO()):
+            self._coco_api = COCO(json_file)
+
+        # Test set json files do not contain annotations (evaluation must be
+        # performed using the COCO evaluation server).
+        self._do_evaluation = "annotations" in self._coco_api.dataset
+        if self._do_evaluation:
+            self._kpt_oks_sigmas = kpt_oks_sigmas
+
+    def reset(self):
+        self._predictions = []
+
+    def process(self, inputs, outputs):
+        """
+        Args:
+            inputs: the inputs to a COCO model (e.g., GeneralizedRCNN).
+                It is a list of dict. Each dict corresponds to an image and
+                contains keys like "height", "width", "file_name", "image_id".
+            outputs: the outputs of a COCO model. It is a list of dicts with key
+                "instances" that contains :class:`Instances`.
+        """
+        for input, output in zip(inputs, outputs):
+            prediction = {"image_id": input["image_id"]}
+
+            if "instances" in output:
+                instances = output["instances"].to(self._cpu_device)
+                prediction["instances"] = instances_to_coco_json(instances, input["image_id"])
+            if "proposals" in output:
+                prediction["proposals"] = output["proposals"].to(self._cpu_device)
+            if len(prediction) > 1:
+                self._predictions.append(prediction)
+
+    def evaluate(self, img_ids=None):
+        """
+        Args:
+            img_ids: a list of image IDs to evaluate on. Default to None for the whole dataset
+        """
+        if self._distributed:
+            comm.synchronize()
+            predictions = comm.gather(self._predictions, dst=0)
+            predictions = list(itertools.chain(*predictions))
+
+            if not comm.is_main_process():
+                return {}
+        else:
+            predictions = self._predictions
+
+        if len(predictions) == 0:
+            self._logger.warning("[COCOEvaluator] Did not receive valid predictions.")
+            return {}
+
+        if self._output_dir:
+            PathManager.mkdirs(self._output_dir)
+            file_path = os.path.join(self._output_dir, "instances_predictions.pth")
+            with PathManager.open(file_path, "wb") as f:
+                torch.save(predictions, f)
+
+        self._results = OrderedDict()
+        if "proposals" in predictions[0]:
+            self._eval_box_proposals(predictions)
+        if "instances" in predictions[0]:
+            self._eval_predictions(predictions, img_ids=img_ids)
+        # Copy so the caller can do whatever with results
+        return copy.deepcopy(self._results)
+
+    def _tasks_from_predictions(self, predictions):
+        """
+        Get COCO API "tasks" (i.e. iou_type) from COCO-format predictions.
+        """
+        tasks = {"bbox"}
+        for pred in predictions:
+            if "segmentation" in pred:
+                tasks.add("segm")
+            if "keypoints" in pred:
+                tasks.add("keypoints")
+        return sorted(tasks)
+
+    def _eval_predictions(self, predictions, img_ids=None):
+        """
+        Evaluate predictions. Fill self._results with the metrics of the tasks.
+        """
+        self._logger.info("Preparing results for COCO format ...")
+        coco_results = list(itertools.chain(*[x["instances"] for x in predictions]))
+        tasks = self._tasks or self._tasks_from_predictions(coco_results)
+
+        # unmap the category ids for COCO
+        if hasattr(self._metadata, "thing_dataset_id_to_contiguous_id"):
+            dataset_id_to_contiguous_id = self._metadata.thing_dataset_id_to_contiguous_id
+            all_contiguous_ids = list(dataset_id_to_contiguous_id.values())
+            num_classes = len(all_contiguous_ids)
+            assert min(all_contiguous_ids) == 0 and max(all_contiguous_ids) == num_classes - 1
+
+            reverse_id_mapping = {v: k for k, v in dataset_id_to_contiguous_id.items()}
+            for result in coco_results:
+                category_id = result["category_id"]
+                assert category_id < num_classes, (
+                    f"A prediction has class={category_id}, "
+                    f"but the dataset only has {num_classes} classes and "
+                    f"predicted class id should be in [0, {num_classes - 1}]."
+                )
+                result["category_id"] = reverse_id_mapping[category_id]
+
+        if self._output_dir:
+            file_path = os.path.join(self._output_dir, "coco_instances_results.json")
+            self._logger.info("Saving results to {}".format(file_path))
+            with PathManager.open(file_path, "w") as f:
+                f.write(json.dumps(coco_results))
+                f.flush()
+
+        if not self._do_evaluation:
+            self._logger.info("Annotations are not available for evaluation.")
+            return
+
+        self._logger.info(
+            "Evaluating predictions with {} COCO API...".format(
+                "unofficial" if self._use_fast_impl else "official"
+            )
+        )
+        for task in sorted(tasks):
+            assert task in {"bbox", "segm", "keypoints"}, f"Got unknown task: {task}!"
+            coco_eval = (
+                _evaluate_predictions_on_coco(
+                    self._coco_api,
+                    coco_results,
+                    task,
+                    kpt_oks_sigmas=self._kpt_oks_sigmas,
+                    cocoeval_fn=COCOeval_opt if self._use_fast_impl else COCOeval,
+                    img_ids=img_ids,
+                    max_dets_per_image=self._max_dets_per_image,
+                )
+                if len(coco_results) > 0
+                else None  # cocoapi does not handle empty results very well
+            )
+
+            res = self._derive_coco_results(
+                coco_eval, task, class_names=self._metadata.get("thing_classes")
+            )
+            self._results[task] = res
+
+    def _eval_box_proposals(self, predictions):
+        """
+        Evaluate the box proposals in predictions.
+        Fill self._results with the metrics for "box_proposals" task.
+        """
+        if self._output_dir:
+            # Saving generated box proposals to file.
+            # Predicted box_proposals are in XYXY_ABS mode.
+            bbox_mode = BoxMode.XYXY_ABS.value
+            ids, boxes, objectness_logits = [], [], []
+            for prediction in predictions:
+                ids.append(prediction["image_id"])
+                boxes.append(prediction["proposals"].proposal_boxes.tensor.numpy())
+                objectness_logits.append(prediction["proposals"].objectness_logits.numpy())
+
+            proposal_data = {
+                "boxes": boxes,
+                "objectness_logits": objectness_logits,
+                "ids": ids,
+                "bbox_mode": bbox_mode,
+            }
+            with PathManager.open(os.path.join(self._output_dir, "box_proposals.pkl"), "wb") as f:
+                pickle.dump(proposal_data, f)
+
+        if not self._do_evaluation:
+            self._logger.info("Annotations are not available for evaluation.")
+            return
+
+        self._logger.info("Evaluating bbox proposals ...")
+        res = {}
+        areas = {"all": "", "small": "s", "medium": "m", "large": "l"}
+        for limit in [100, 1000]:
+            for area, suffix in areas.items():
+                stats = _evaluate_box_proposals(predictions, self._coco_api, area=area, limit=limit)
+                key = "AR{}@{:d}".format(suffix, limit)
+                res[key] = float(stats["ar"].item() * 100)
+        self._logger.info("Proposal metrics: \n" + create_small_table(res))
+        self._results["box_proposals"] = res
+
+    def _derive_coco_results(self, coco_eval, iou_type, class_names=None):
+        """
+        Derive the desired score numbers from summarized COCOeval.
+
+        Args:
+            coco_eval (None or COCOEval): None represents no predictions from model.
+            iou_type (str):
+            class_names (None or list[str]): if provided, will use it to predict
+                per-category AP.
+
+        Returns:
+            a dict of {metric name: score}
+        """
+
+        metrics = {
+            "bbox": ["AP", "AP50", "AP75", "APs", "APm", "APl"],
+            "segm": ["AP", "AP50", "AP75", "APs", "APm", "APl"],
+            "keypoints": ["AP", "AP50", "AP75", "APm", "APl"],
+        }[iou_type]
+
+        if coco_eval is None:
+            self._logger.warn("No predictions from the model!")
+            return {metric: float("nan") for metric in metrics}
+
+        # the standard metrics
+        results = {
+            metric: float(coco_eval.stats[idx] * 100 if coco_eval.stats[idx] >= 0 else "nan")
+            for idx, metric in enumerate(metrics)
+        }
+        self._logger.info(
+            "Evaluation results for {}: \n".format(iou_type) + create_small_table(results)
+        )
+        if not np.isfinite(sum(results.values())):
+            self._logger.info("Some metrics cannot be computed and is shown as NaN.")
+
+        if class_names is None or len(class_names) <= 1:
+            return results
+        # Compute per-category AP
+        # from https://github.com/facebookresearch/Detectron/blob/a6a835f5b8208c45d0dce217ce9bbda915f44df7/detectron/datasets/json_dataset_evaluator.py#L222-L252 # noqa
+        precisions = coco_eval.eval["precision"]
+        # precision has dims (iou, recall, cls, area range, max dets)
+        assert len(class_names) == precisions.shape[2]
+
+        results_per_category = []
+        for idx, name in enumerate(class_names):
+            # area range index 0: all area ranges
+            # max dets index -1: typically 100 per image
+            precision = precisions[:, :, idx, 0, -1]
+            precision = precision[precision > -1]
+            ap = np.mean(precision) if precision.size else float("nan")
+            results_per_category.append(("{}".format(name), float(ap * 100)))
+
+        # tabulate it
+        N_COLS = min(6, len(results_per_category) * 2)
+        results_flatten = list(itertools.chain(*results_per_category))
+        results_2d = itertools.zip_longest(*[results_flatten[i::N_COLS] for i in range(N_COLS)])
+        table = tabulate(
+            results_2d,
+            tablefmt="pipe",
+            floatfmt=".3f",
+            headers=["category", "AP"] * (N_COLS // 2),
+            numalign="left",
+        )
+        self._logger.info("Per-category {} AP: \n".format(iou_type) + table)
+
+        results.update({"AP-" + name: ap for name, ap in results_per_category})
+        return results
+
+
+def instances_to_coco_json(instances, img_id):
+    """
+    Dump an "Instances" object to a COCO-format json that's used for evaluation.
+
+    Args:
+        instances (Instances):
+        img_id (int): the image id
+
+    Returns:
+        list[dict]: list of json annotations in COCO format.
+    """
+    num_instance = len(instances)
+    if num_instance == 0:
+        return []
+
+    boxes = instances.pred_boxes.tensor.numpy()
+    boxes = BoxMode.convert(boxes, BoxMode.XYXY_ABS, BoxMode.XYWH_ABS)
+    boxes = boxes.tolist()
+    scores = instances.scores.tolist()
+    classes = instances.pred_classes.tolist()
+
+    has_mask = instances.has("pred_masks")
+    if has_mask:
+        # use RLE to encode the masks, because they are too large and takes memory
+        # since this evaluator stores outputs of the entire dataset
+        rles = [
+            mask_util.encode(np.array(mask[:, :, None], order="F", dtype="uint8"))[0]
+            for mask in instances.pred_masks
+        ]
+        for rle in rles:
+            # "counts" is an array encoded by mask_util as a byte-stream. Python3's
+            # json writer which always produces strings cannot serialize a bytestream
+            # unless you decode it. Thankfully, utf-8 works out (which is also what
+            # the pycocotools/_mask.pyx does).
+            rle["counts"] = rle["counts"].decode("utf-8")
+
+    has_keypoints = instances.has("pred_keypoints")
+    if has_keypoints:
+        keypoints = instances.pred_keypoints
+
+    results = []
+    for k in range(num_instance):
+        result = {
+            "image_id": img_id,
+            "category_id": classes[k],
+            "bbox": boxes[k],
+            "score": scores[k],
+        }
+        if has_mask:
+            result["segmentation"] = rles[k]
+        if has_keypoints:
+            # In COCO annotations,
+            # keypoints coordinates are pixel indices.
+            # However our predictions are floating point coordinates.
+            # Therefore we subtract 0.5 to be consistent with the annotation format.
+            # This is the inverse of data loading logic in `datasets/coco.py`.
+            keypoints[k][:, :2] -= 0.5
+            result["keypoints"] = keypoints[k].flatten().tolist()
+        results.append(result)
+    return results
+
+
+# inspired from Detectron:
+# https://github.com/facebookresearch/Detectron/blob/a6a835f5b8208c45d0dce217ce9bbda915f44df7/detectron/datasets/json_dataset_evaluator.py#L255 # noqa
+def _evaluate_box_proposals(dataset_predictions, coco_api, thresholds=None, area="all", limit=None):
+    """
+    Evaluate detection proposal recall metrics. This function is a much
+    faster alternative to the official COCO API recall evaluation code. However,
+    it produces slightly different results.
+    """
+    # Record max overlap value for each gt box
+    # Return vector of overlap values
+    areas = {
+        "all": 0,
+        "small": 1,
+        "medium": 2,
+        "large": 3,
+        "96-128": 4,
+        "128-256": 5,
+        "256-512": 6,
+        "512-inf": 7,
+    }
+    area_ranges = [
+        [0**2, 1e5**2],  # all
+        [0**2, 32**2],  # small
+        [32**2, 96**2],  # medium
+        [96**2, 1e5**2],  # large
+        [96**2, 128**2],  # 96-128
+        [128**2, 256**2],  # 128-256
+        [256**2, 512**2],  # 256-512
+        [512**2, 1e5**2],
+    ]  # 512-inf
+    assert area in areas, "Unknown area range: {}".format(area)
+    area_range = area_ranges[areas[area]]
+    gt_overlaps = []
+    num_pos = 0
+
+    for prediction_dict in dataset_predictions:
+        predictions = prediction_dict["proposals"]
+
+        # sort predictions in descending order
+        # TODO maybe remove this and make it explicit in the documentation
+        inds = predictions.objectness_logits.sort(descending=True)[1]
+        predictions = predictions[inds]
+
+        ann_ids = coco_api.getAnnIds(imgIds=prediction_dict["image_id"])
+        anno = coco_api.loadAnns(ann_ids)
+        gt_boxes = [
+            BoxMode.convert(obj["bbox"], BoxMode.XYWH_ABS, BoxMode.XYXY_ABS)
+            for obj in anno
+            if obj["iscrowd"] == 0
+        ]
+        gt_boxes = torch.as_tensor(gt_boxes).reshape(-1, 4)  # guard against no boxes
+        gt_boxes = Boxes(gt_boxes)
+        gt_areas = torch.as_tensor([obj["area"] for obj in anno if obj["iscrowd"] == 0])
+
+        if len(gt_boxes) == 0 or len(predictions) == 0:
+            continue
+
+        valid_gt_inds = (gt_areas >= area_range[0]) & (gt_areas <= area_range[1])
+        gt_boxes = gt_boxes[valid_gt_inds]
+
+        num_pos += len(gt_boxes)
+
+        if len(gt_boxes) == 0:
+            continue
+
+        if limit is not None and len(predictions) > limit:
+            predictions = predictions[:limit]
+
+        overlaps = pairwise_iou(predictions.proposal_boxes, gt_boxes)
+
+        _gt_overlaps = torch.zeros(len(gt_boxes))
+        for j in range(min(len(predictions), len(gt_boxes))):
+            # find which proposal box maximally covers each gt box
+            # and get the iou amount of coverage for each gt box
+            max_overlaps, argmax_overlaps = overlaps.max(dim=0)
+
+            # find which gt box is 'best' covered (i.e. 'best' = most iou)
+            gt_ovr, gt_ind = max_overlaps.max(dim=0)
+            assert gt_ovr >= 0
+            # find the proposal box that covers the best covered gt box
+            box_ind = argmax_overlaps[gt_ind]
+            # record the iou coverage of this gt box
+            _gt_overlaps[j] = overlaps[box_ind, gt_ind]
+            assert _gt_overlaps[j] == gt_ovr
+            # mark the proposal box and the gt box as used
+            overlaps[box_ind, :] = -1
+            overlaps[:, gt_ind] = -1
+
+        # append recorded iou coverage level
+        gt_overlaps.append(_gt_overlaps)
+    gt_overlaps = (
+        torch.cat(gt_overlaps, dim=0) if len(gt_overlaps) else torch.zeros(0, dtype=torch.float32)
+    )
+    gt_overlaps, _ = torch.sort(gt_overlaps)
+
+    if thresholds is None:
+        step = 0.05
+        thresholds = torch.arange(0.5, 0.95 + 1e-5, step, dtype=torch.float32)
+    recalls = torch.zeros_like(thresholds)
+    # compute recall for each iou threshold
+    for i, t in enumerate(thresholds):
+        recalls[i] = (gt_overlaps >= t).float().sum() / float(num_pos)
+    # ar = 2 * np.trapz(recalls, thresholds)
+    ar = recalls.mean()
+    return {
+        "ar": ar,
+        "recalls": recalls,
+        "thresholds": thresholds,
+        "gt_overlaps": gt_overlaps,
+        "num_pos": num_pos,
+    }
+
+
+def _evaluate_predictions_on_coco(
+    coco_gt,
+    coco_results,
+    iou_type,
+    kpt_oks_sigmas=None,
+    cocoeval_fn=COCOeval_opt,
+    img_ids=None,
+    max_dets_per_image=None,
+):
+    """
+    Evaluate the coco results using COCOEval API.
+    """
+    assert len(coco_results) > 0
+
+    if iou_type == "segm":
+        coco_results = copy.deepcopy(coco_results)
+        # When evaluating mask AP, if the results contain bbox, cocoapi will
+        # use the box area as the area of the instance, instead of the mask area.
+        # This leads to a different definition of small/medium/large.
+        # We remove the bbox field to let mask AP use mask area.
+        for c in coco_results:
+            c.pop("bbox", None)
+
+    coco_dt = coco_gt.loadRes(coco_results)
+    coco_eval = cocoeval_fn(coco_gt, coco_dt, iou_type)
+    # For COCO, the default max_dets_per_image is [1, 10, 100].
+    if max_dets_per_image is None:
+        max_dets_per_image = [1, 10, 100]  # Default from COCOEval
+    else:
+        assert (
+            len(max_dets_per_image) >= 3
+        ), "COCOeval requires maxDets (and max_dets_per_image) to have length at least 3"
+        # In the case that user supplies a custom input for max_dets_per_image,
+        # apply COCOevalMaxDets to evaluate AP with the custom input.
+        if max_dets_per_image[2] != 100:
+            coco_eval = COCOevalMaxDets(coco_gt, coco_dt, iou_type)
+    if iou_type != "keypoints":
+        coco_eval.params.maxDets = max_dets_per_image
+
+    if img_ids is not None:
+        coco_eval.params.imgIds = img_ids
+
+    if iou_type == "keypoints":
+        # Use the COCO default keypoint OKS sigmas unless overrides are specified
+        if kpt_oks_sigmas:
+            assert hasattr(coco_eval.params, "kpt_oks_sigmas"), "pycocotools is too old!"
+            coco_eval.params.kpt_oks_sigmas = np.array(kpt_oks_sigmas)
+        # COCOAPI requires every detection and every gt to have keypoints, so
+        # we just take the first entry from both
+        num_keypoints_dt = len(coco_results[0]["keypoints"]) // 3
+        num_keypoints_gt = len(next(iter(coco_gt.anns.values()))["keypoints"]) // 3
+        num_keypoints_oks = len(coco_eval.params.kpt_oks_sigmas)
+        assert num_keypoints_oks == num_keypoints_dt == num_keypoints_gt, (
+            f"[COCOEvaluator] Prediction contain {num_keypoints_dt} keypoints. "
+            f"Ground truth contains {num_keypoints_gt} keypoints. "
+            f"The length of cfg.TEST.KEYPOINT_OKS_SIGMAS is {num_keypoints_oks}. "
+            "They have to agree with each other. For meaning of OKS, please refer to "
+            "http://cocodataset.org/#keypoints-eval."
+        )
+
+    coco_eval.evaluate()
+    coco_eval.accumulate()
+    coco_eval.summarize()
+
+    return coco_eval
+
+
+class COCOevalMaxDets(COCOeval):
+    """
+    Modified version of COCOeval for evaluating AP with a custom
+    maxDets (by default for COCO, maxDets is 100)
+    """
+
+    def summarize(self):
+        """
+        Compute and display summary metrics for evaluation results given
+        a custom value for  max_dets_per_image
+        """
+
+        def _summarize(ap=1, iouThr=None, areaRng="all", maxDets=100):
+            p = self.params
+            iStr = " {:<18} {} @[ IoU={:<9} | area={:>6s} | maxDets={:>3d} ] = {:0.3f}"
+            titleStr = "Average Precision" if ap == 1 else "Average Recall"
+            typeStr = "(AP)" if ap == 1 else "(AR)"
+            iouStr = (
+                "{:0.2f}:{:0.2f}".format(p.iouThrs[0], p.iouThrs[-1])
+                if iouThr is None
+                else "{:0.2f}".format(iouThr)
+            )
+
+            aind = [i for i, aRng in enumerate(p.areaRngLbl) if aRng == areaRng]
+            mind = [i for i, mDet in enumerate(p.maxDets) if mDet == maxDets]
+            if ap == 1:
+                # dimension of precision: [TxRxKxAxM]
+                s = self.eval["precision"]
+                # IoU
+                if iouThr is not None:
+                    t = np.where(iouThr == p.iouThrs)[0]
+                    s = s[t]
+                s = s[:, :, :, aind, mind]
+            else:
+                # dimension of recall: [TxKxAxM]
+                s = self.eval["recall"]
+                if iouThr is not None:
+                    t = np.where(iouThr == p.iouThrs)[0]
+                    s = s[t]
+                s = s[:, :, aind, mind]
+            if len(s[s > -1]) == 0:
+                mean_s = -1
+            else:
+                mean_s = np.mean(s[s > -1])
+            print(iStr.format(titleStr, typeStr, iouStr, areaRng, maxDets, mean_s))
+            return mean_s
+
+        def _summarizeDets():
+            stats = np.zeros((12,))
+            # Evaluate AP using the custom limit on maximum detections per image
+            stats[0] = _summarize(1, maxDets=self.params.maxDets[2])
+            stats[1] = _summarize(1, iouThr=0.5, maxDets=self.params.maxDets[2])
+            stats[2] = _summarize(1, iouThr=0.75, maxDets=self.params.maxDets[2])
+            stats[3] = _summarize(1, areaRng="small", maxDets=self.params.maxDets[2])
+            stats[4] = _summarize(1, areaRng="medium", maxDets=self.params.maxDets[2])
+            stats[5] = _summarize(1, areaRng="large", maxDets=self.params.maxDets[2])
+            stats[6] = _summarize(0, maxDets=self.params.maxDets[0])
+            stats[7] = _summarize(0, maxDets=self.params.maxDets[1])
+            stats[8] = _summarize(0, maxDets=self.params.maxDets[2])
+            stats[9] = _summarize(0, areaRng="small", maxDets=self.params.maxDets[2])
+            stats[10] = _summarize(0, areaRng="medium", maxDets=self.params.maxDets[2])
+            stats[11] = _summarize(0, areaRng="large", maxDets=self.params.maxDets[2])
+            return stats
+
+        def _summarizeKps():
+            stats = np.zeros((10,))
+            stats[0] = _summarize(1, maxDets=20)
+            stats[1] = _summarize(1, maxDets=20, iouThr=0.5)
+            stats[2] = _summarize(1, maxDets=20, iouThr=0.75)
+            stats[3] = _summarize(1, maxDets=20, areaRng="medium")
+            stats[4] = _summarize(1, maxDets=20, areaRng="large")
+            stats[5] = _summarize(0, maxDets=20)
+            stats[6] = _summarize(0, maxDets=20, iouThr=0.5)
+            stats[7] = _summarize(0, maxDets=20, iouThr=0.75)
+            stats[8] = _summarize(0, maxDets=20, areaRng="medium")
+            stats[9] = _summarize(0, maxDets=20, areaRng="large")
+            return stats
+
+        if not self.eval:
+            raise Exception("Please run accumulate() first")
+        iouType = self.params.iouType
+        if iouType == "segm" or iouType == "bbox":
+            summarize = _summarizeDets
+        elif iouType == "keypoints":
+            summarize = _summarizeKps
+        self.stats = summarize()
+
+    def __str__(self):
+        self.summarize()

detectron2/evaluation/evaluator.py

@@ -0,0 +1,233 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+import datetime
+import logging
+import time
+from collections import OrderedDict, abc
+from contextlib import ExitStack, contextmanager
+from typing import List, Union
+import torch
+from torch import nn
+
+from detectron2.utils.comm import get_world_size, is_main_process
+from detectron2.utils.logger import log_every_n_seconds
+
+
+class DatasetEvaluator:
+    """
+    Base class for a dataset evaluator.
+
+    The function :func:`inference_on_dataset` runs the model over
+    all samples in the dataset, and have a DatasetEvaluator to process the inputs/outputs.
+
+    This class will accumulate information of the inputs/outputs (by :meth:`process`),
+    and produce evaluation results in the end (by :meth:`evaluate`).
+    """
+
+    def reset(self):
+        """
+        Preparation for a new round of evaluation.
+        Should be called before starting a round of evaluation.
+        """
+        pass
+
+    def process(self, inputs, outputs):
+        """
+        Process the pair of inputs and outputs.
+        If they contain batches, the pairs can be consumed one-by-one using `zip`:
+
+        .. code-block:: python
+
+            for input_, output in zip(inputs, outputs):
+                # do evaluation on single input/output pair
+                ...
+
+        Args:
+            inputs (list): the inputs that's used to call the model.
+            outputs (list): the return value of `model(inputs)`
+        """
+        pass
+
+    def evaluate(self):
+        """
+        Evaluate/summarize the performance, after processing all input/output pairs.
+
+        Returns:
+            dict:
+                A new evaluator class can return a dict of arbitrary format
+                as long as the user can process the results.
+                In our train_net.py, we expect the following format:
+
+                * key: the name of the task (e.g., bbox)
+                * value: a dict of {metric name: score}, e.g.: {"AP50": 80}
+        """
+        pass
+
+
+class DatasetEvaluators(DatasetEvaluator):
+    """
+    Wrapper class to combine multiple :class:`DatasetEvaluator` instances.
+
+    This class dispatches every evaluation call to
+    all of its :class:`DatasetEvaluator`.
+    """
+
+    def __init__(self, evaluators):
+        """
+        Args:
+            evaluators (list): the evaluators to combine.
+        """
+        super().__init__()
+        self._evaluators = evaluators
+
+    def reset(self):
+        for evaluator in self._evaluators:
+            evaluator.reset()
+
+    def process(self, inputs, outputs):
+        for evaluator in self._evaluators:
+            evaluator.process(inputs, outputs)
+
+    def evaluate(self):
+        results = OrderedDict()
+        for evaluator in self._evaluators:
+            result = evaluator.evaluate()
+            if is_main_process() and result is not None:
+                for k, v in result.items():
+                    assert (
+                        k not in results
+                    ), "Different evaluators produce results with the same key {}".format(k)
+                    results[k] = v
+        return results
+
+
+def inference_on_dataset(
+    model,
+    data_loader,
+    evaluator: Union[DatasetEvaluator, List[DatasetEvaluator], None],
+    callbacks=None,
+):
+    """
+    Run model on the data_loader and evaluate the metrics with evaluator.
+    Also benchmark the inference speed of `model.__call__` accurately.
+    The model will be used in eval mode.
+
+    Args:
+        model (callable): a callable which takes an object from
+            `data_loader` and returns some outputs.
+
+            If it's an nn.Module, it will be temporarily set to `eval` mode.
+            If you wish to evaluate a model in `training` mode instead, you can
+            wrap the given model and override its behavior of `.eval()` and `.train()`.
+        data_loader: an iterable object with a length.
+            The elements it generates will be the inputs to the model.
+        evaluator: the evaluator(s) to run. Use `None` if you only want to benchmark,
+            but don't want to do any evaluation.
+        callbacks (dict of callables): a dictionary of callback functions which can be
+            called at each stage of inference.
+
+    Returns:
+        The return value of `evaluator.evaluate()`
+    """
+    num_devices = get_world_size()
+    logger = logging.getLogger(__name__)
+    logger.info("Start inference on {} batches".format(len(data_loader)))
+
+    total = len(data_loader)  # inference data loader must have a fixed length
+    if evaluator is None:
+        # create a no-op evaluator
+        evaluator = DatasetEvaluators([])
+    if isinstance(evaluator, abc.MutableSequence):
+        evaluator = DatasetEvaluators(evaluator)
+    evaluator.reset()
+
+    num_warmup = min(5, total - 1)
+    start_time = time.perf_counter()
+    total_data_time = 0
+    total_compute_time = 0
+    total_eval_time = 0
+    with ExitStack() as stack:
+        if isinstance(model, nn.Module):
+            stack.enter_context(inference_context(model))
+        stack.enter_context(torch.no_grad())
+
+        start_data_time = time.perf_counter()
+        dict.get(callbacks or {}, "on_start", lambda: None)()
+        for idx, inputs in enumerate(data_loader):
+            total_data_time += time.perf_counter() - start_data_time
+            if idx == num_warmup:
+                start_time = time.perf_counter()
+                total_data_time = 0
+                total_compute_time = 0
+                total_eval_time = 0
+
+            start_compute_time = time.perf_counter()
+            dict.get(callbacks or {}, "before_inference", lambda: None)()
+            outputs = model(inputs)
+            dict.get(callbacks or {}, "after_inference", lambda: None)()
+            if torch.cuda.is_available():
+                torch.cuda.synchronize()
+            total_compute_time += time.perf_counter() - start_compute_time
+
+            start_eval_time = time.perf_counter()
+            evaluator.process(inputs, outputs)
+            total_eval_time += time.perf_counter() - start_eval_time
+
+            iters_after_start = idx + 1 - num_warmup * int(idx >= num_warmup)
+            data_seconds_per_iter = total_data_time / iters_after_start
+            compute_seconds_per_iter = total_compute_time / iters_after_start
+            eval_seconds_per_iter = total_eval_time / iters_after_start
+            total_seconds_per_iter = (time.perf_counter() - start_time) / iters_after_start
+            if idx >= num_warmup * 2 or compute_seconds_per_iter > 5:
+                eta = datetime.timedelta(seconds=int(total_seconds_per_iter * (total - idx - 1)))
+                log_every_n_seconds(
+                    logging.INFO,
+                    (
+                        f"Inference done {idx + 1}/{total}. "
+                        f"Dataloading: {data_seconds_per_iter:.4f} s/iter. "
+                        f"Inference: {compute_seconds_per_iter:.4f} s/iter. "
+                        f"Eval: {eval_seconds_per_iter:.4f} s/iter. "
+                        f"Total: {total_seconds_per_iter:.4f} s/iter. "
+                        f"ETA={eta}"
+                    ),
+                    n=5,
+                )
+            start_data_time = time.perf_counter()
+        dict.get(callbacks or {}, "on_end", lambda: None)()
+
+    # Measure the time only for this worker (before the synchronization barrier)
+    total_time = time.perf_counter() - start_time
+    total_time_str = str(datetime.timedelta(seconds=total_time))
+    # NOTE this format is parsed by grep
+    logger.info(
+        "Total inference time: {} ({:.6f} s / iter per device, on {} devices)".format(
+            total_time_str, total_time / (total - num_warmup), num_devices
+        )
+    )
+    total_compute_time_str = str(datetime.timedelta(seconds=int(total_compute_time)))
+    logger.info(
+        "Total inference pure compute time: {} ({:.6f} s / iter per device, on {} devices)".format(
+            total_compute_time_str, total_compute_time / (total - num_warmup), num_devices
+        )
+    )
+
+    results = evaluator.evaluate()
+    # An evaluator may return None when not in main process.
+    # Replace it by an empty dict instead to make it easier for downstream code to handle
+    if results is None:
+        results = {}
+    return results
+
+
+@contextmanager
+def inference_context(model):
+    """
+    A context where the model is temporarily changed to eval mode,
+    and restored to previous mode afterwards.
+
+    Args:
+        model: a torch Module
+    """
+    training_mode = model.training
+    model.eval()
+    yield
+    model.train(training_mode)