Source code for pypots.optim.lr_scheduler.multiplicative_lrs

"""
Multiplicative learning rate scheduler.
"""

# Created by Wenjie Du <wenjay.du@gmail.com>
# License: BSD-3-Clause


from .base import LRScheduler, logger


[docs] class MultiplicativeLR(LRScheduler): """Multiply the learning rate of each parameter group by the factor given in the specified function. When last_epoch=-1, sets initial lr as lr. Parameters ---------- lr_lambda: Callable or list, A function which computes a multiplicative factor given an integer parameter epoch, or a list of such functions, one for each group in optimizer.param_groups. last_epoch: int, The index of last epoch. Default: -1. verbose: bool, If ``True``, prints a message to stdout for each update. Default: ``False``. Notes ----- This class works the same with ``torch.optim.lr_scheduler.MultiplicativeLR``. The only difference that is also why we implement them is that you don't have to pass according optimizers into them immediately while initializing them. Example ------- >>> lmbda = lambda epoch: 0.95 >>> # xdoctest: +SKIP >>> scheduler = MultiplicativeLR(lr_lambda=lmbda) >>> adam = pypots.optim.Adam(lr=1e-3, lr_scheduler=scheduler) """ def __init__(self, lr_lambda, last_epoch=-1, verbose=False): super().__init__(last_epoch, verbose) self.lr_lambda = lr_lambda self.lr_lambdas = None
[docs] def init_scheduler(self, optimizer): if not isinstance(self.lr_lambda, list) and not isinstance( self.lr_lambda, tuple ): self.lr_lambdas = [self.lr_lambda] * len(optimizer.param_groups) else: if len(self.lr_lambda) != len(optimizer.param_groups): raise ValueError( "Expected {} lr_lambdas, but got {}".format( len(optimizer.param_groups), len(self.lr_lambda) ) ) self.lr_lambdas = list(self.lr_lambda) super().init_scheduler(optimizer)
[docs] def get_lr(self): if not self._get_lr_called_within_step: logger.warning( "⚠️ To get the last learning rate computed by the scheduler, " "please use `get_last_lr()`.", ) if self.last_epoch > 0: return [ group["lr"] * lmbda(self.last_epoch) for lmbda, group in zip(self.lr_lambdas, self.optimizer.param_groups) ] else: return [group["lr"] for group in self.optimizer.param_groups]