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import numpy as np
class NoneSchedule(object):
def __init__(self, optimizer, lr):
self.optimizer = optimizer
self.constant_lr = lr
self.step(0)
def step(self, num_updates):
self.lr = self.constant_lr
for param_group in self.optimizer.param_groups:
param_group['lr'] = self.lr
return self.lr
def get_lr(self):
return self.optimizer.param_groups[0]['lr']
def get_last_lr(self):
return self.get_lr()
class RSQRTSchedule(NoneSchedule):
def __init__(self, optimizer, lr, warmup_updates, hidden_size):
self.optimizer = optimizer
self.constant_lr = lr
self.warmup_updates = warmup_updates
self.hidden_size = hidden_size
self.lr = lr
for param_group in optimizer.param_groups:
param_group['lr'] = self.lr
self.step(0)
def step(self, num_updates):
constant_lr = self.constant_lr
warmup = min(num_updates / self.warmup_updates, 1.0)
rsqrt_decay = max(self.warmup_updates, num_updates) ** -0.5
rsqrt_hidden = self.hidden_size ** -0.5
self.lr = max(constant_lr * warmup * rsqrt_decay * rsqrt_hidden, 1e-6)
for param_group in self.optimizer.param_groups:
param_group['lr'] = self.lr
return self.lr
class WarmupSchedule(NoneSchedule):
def __init__(self, optimizer, lr, warmup_updates):
self.optimizer = optimizer
self.constant_lr = self.lr = lr
self.warmup_updates = warmup_updates
for param_group in optimizer.param_groups:
param_group['lr'] = self.lr
self.step(0)
def step(self, num_updates):
constant_lr = self.constant_lr
warmup = min(num_updates / self.warmup_updates, 1.0)
self.lr = max(constant_lr * warmup, 1e-7)
for param_group in self.optimizer.param_groups:
param_group['lr'] = self.lr
return self.lr
class CosineSchedule(NoneSchedule):
def __init__(self, optimizer, lr, warmup_updates, total_updates):
self.optimizer = optimizer
self.constant_lr = lr
self.warmup_updates = warmup_updates
self.total_updates = total_updates
self.lr = lr
self.assign_learning_rate(self.optimizer, self.lr)
self.step(0)
def assign_learning_rate(self, optimizer, new_lr):
for param_group in optimizer.param_groups:
param_group["lr"] = new_lr
def _warmup_lr(self, base_lr, warmup_length, step):
return base_lr * (step + 1) / warmup_length
def step(self, num_updates):
if num_updates < self.warmup_updates:
lr = self._warmup_lr(self.lr, self.warmup_updates, num_updates)
else:
e = num_updates - self.warmup_updates
es = self.total_updates - self.warmup_updates
lr = 0.5 * (1 + np.cos(np.pi * e / es)) * self.lr
self.assign_learning_rate(self.optimizer, lr)
return lr
if __name__ == '__main__':
import numpy as np
import matplotlib.pyplot as plt
import torch
def plot_scheduler(scheduler, label=None):
y = np.array([scheduler.step(x) for x in range(0,160000, 10)])
x = np.arange(0,160000, 10)
plt.plot(x, y, label=label)
dummy_model = torch.nn.Linear(10,10)
dummy_optimizer = torch.optim.Adam(dummy_model.parameters())
rsqrt = CosineSchedule(dummy_optimizer, lr=0.0005, warmup_updates=10000, total_updates=160000)
plot_scheduler(rsqrt, "8000")
plt.savefig("0.png")