<reponame>DetectionTeamUCAS/RetinaNet_Tensorflow
# Copyright 2016 The TensorFlow Authors. All Rights Reserved.
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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# distributed under the License is distributed on an "AS IS" BASIS,
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# ==============================================================================
"""Contains a model definition for AlexNet.

This work was first described in:
  ImageNet Classification with Deep Convolutional Neural Networks
  <NAME>, <NAME> and <NAME>

and later refined in:
  One weird trick for parallelizing convolutional neural networks
  <NAME>, 2014

Here we provide the implementation proposed in "One weird trick" and not
"ImageNet Classification", as per the paper, the LRN layers have been removed.

Usage:
  with slim.arg_scope(alexnet.alexnet_v2_arg_scope()):
    outputs, end_points = alexnet.alexnet_v2(inputs)

@@alexnet_v2
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow as tf

slim = tf.contrib.slim
trunc_normal = lambda stddev: tf.truncated_normal_initializer(0.0, stddev)


def alexnet_v2_arg_scope(weight_decay=0.0005):
  with slim.arg_scope([slim.conv2d, slim.fully_connected],
                      activation_fn=tf.nn.relu,
                      biases_initializer=tf.constant_initializer(0.1),
                      weights_regularizer=slim.l2_regularizer(weight_decay)):
    with slim.arg_scope([slim.conv2d], padding='SAME'):
      with slim.arg_scope([slim.max_pool2d], padding='VALID') as arg_sc:
        return arg_sc


def alexnet_v2(inputs,
               num_classes=1000,
               is_training=True,
               dropout_keep_prob=0.5,
               spatial_squeeze=True,
               scope='alexnet_v2'):
  """AlexNet version 2.

  Described in: http://arxiv.org/pdf/1404.5997v2.pdf
  Parameters from:
  github.com/akrizhevsky/cuda-convnet2/blob/master/layers/
  layers-imagenet-1gpu.cfg

  Note: All the fully_connected layers have been transformed to conv2d layers.
        To use in classification mode, resize input to 224x224. To use in fully
        convolutional mode, set spatial_squeeze to false.
        The LRN layers have been removed and change the initializers from
        random_normal_initializer to xavier_initializer.

  Args:
    inputs: a tensor of size [batch_size, height, width, channels].
    num_classes: number of predicted classes.
    is_training: whether or not the model is being trained.
    dropout_keep_prob: the probability that activations are kept in the dropout
      layers during training.
    spatial_squeeze: whether or not should squeeze the spatial dimensions of the
      outputs. Useful to remove unnecessary dimensions for classification.
    scope: Optional scope for the variables.

  Returns:
    the last op containing the log predictions and end_points dict.
  """
  with tf.variable_scope(scope, 'alexnet_v2', [inputs]) as sc:
    end_points_collection = sc.name + '_end_points'
    # Collect outputs for conv2d, fully_connected and max_pool2d.
    with slim.arg_scope([slim.conv2d, slim.fully_connected, slim.max_pool2d],
                        outputs_collections=[end_points_collection]):
      net = slim.conv2d(inputs, 64, [11, 11], 4, padding='VALID',
                        scope='conv1')
      net = slim.max_pool2d(net, [3, 3], 2, scope='pool1')
      net = slim.conv2d(net, 192, [5, 5], scope='conv2')
      net = slim.max_pool2d(net, [3, 3], 2, scope='pool2')
      net = slim.conv2d(net, 384, [3, 3], scope='conv3')
      net = slim.conv2d(net, 384, [3, 3], scope='conv4')
      net = slim.conv2d(net, 256, [3, 3], scope='conv5')
      net = slim.max_pool2d(net, [3, 3], 2, scope='pool5')

      # Use conv2d instead of fully_connected layers.
      with slim.arg_scope([slim.conv2d],
                          weights_initializer=trunc_normal(0.005),
                          biases_initializer=tf.constant_initializer(0.1)):
        net = slim.conv2d(net, 4096, [5, 5], padding='VALID',
                          scope='fc6')
        net = slim.dropout(net, dropout_keep_prob, is_training=is_training,
                           scope='dropout6')
        net = slim.conv2d(net, 4096, [1, 1], scope='fc7')
        net = slim.dropout(net, dropout_keep_prob, is_training=is_training,
                           scope='dropout7')
        net = slim.conv2d(net, num_classes, [1, 1],
                          activation_fn=None,
                          normalizer_fn=None,
                          biases_initializer=tf.zeros_initializer(),
                          scope='fc8')

      # Convert end_points_collection into a end_point dict.
      end_points = slim.utils.convert_collection_to_dict(end_points_collection)
      if spatial_squeeze:
        net = tf.squeeze(net, [1, 2], name='fc8/squeezed')
        end_points[sc.name + '/fc8'] = net
      return net, end_points
alexnet_v2.default_image_size = 224
