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ColossalAI/colossalai/nn/lr_scheduler/poly.py

67 lines
2.6 KiB

3 years ago
from torch.optim.lr_scheduler import _LRScheduler
from colossalai.registry import LR_SCHEDULERS
from .delayed import WarmupScheduler
@LR_SCHEDULERS.register_module
class PolynomialLR(_LRScheduler):
"""Polynomial learning rate scheduler.
Args:
optimizer (:class:`torch.optim.Optimizer`): Wrapped optimizer.
total_steps (int): Number of total training steps.
end_lr (float, optional): Minimum learning rate, defaults to 0.0001.
power (float, optional): The power of polynomial, defaults to 1.0.
last_epoch (int, optional): The index of last epoch, defaults to -1. When last_epoch=-1,
the schedule is started from the beginning or When last_epoch=-1, sets initial lr as lr.
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"""
def __init__(self,
optimizer,
total_steps: int,
end_lr: float = 0.0001,
power: float = 1.0,
last_epoch: int = -1,
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**kwargs):
if end_lr < 0:
raise ValueError(f'end_lr must >= 0, got {end_lr}')
self.total_steps = total_steps
self.end_lr = end_lr
self.power = power
super().__init__(optimizer, last_epoch=last_epoch)
def get_lr(self):
return self._get_closed_form_lr()
def _get_closed_form_lr(self):
return [(base_lr - self.end_lr) *
((1 - min(self.last_epoch, self.total_steps) / self.total_steps)**self.power) + self.end_lr
for base_lr in self.base_lrs]
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@LR_SCHEDULERS.register_module
class PolynomialWarmupLR(WarmupScheduler):
"""Polynomial learning rate scheduler with warmup.
Args:
optimizer (:class:`torch.optim.Optimizer`): Wrapped optimizer.
total_steps (int): Number of total training steps.
warmup_steps (int, optional): Number of warmup steps, defaults to 0.
end_lr (float, optional): Minimum learning rate, defaults to 0.0001.
power (float, optional): The power of polynomial, defaults to 1.0.
last_epoch (int, optional): The index of last epoch, defaults to -1. When last_epoch=-1,
the schedule is started from the beginning or When last_epoch=-1, sets initial lr as lr.
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"""
def __init__(self,
optimizer,
total_steps: int,
warmup_steps: int = 0,
end_lr: float = 0.0001,
power: float = 1.0,
last_epoch: int = -1,
**kwargs):
base_scheduler = PolynomialLR(optimizer, total_steps - warmup_steps, end_lr=end_lr, power=power)
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super().__init__(optimizer, warmup_steps, base_scheduler, last_epoch=last_epoch)