ChainedScheduler

class torch.optim.lr_scheduler.ChainedScheduler(schedulers, optimizer=None)

Chains a list of learning rate schedulers.

Takes in a sequence of chainable learning rate schedulers and calls their step() functions consecutively in just one call to step().

Parameters

• schedulers (sequence) – sequence of chained schedulers.

• optimizer (Optimizer, optional) – Wrapped optimizer. Default: None.

Example

>>> # Assuming optimizer uses lr = 1. for all groups
>>> # lr = 0.09     if epoch == 0
>>> # lr = 0.081    if epoch == 1
>>> # lr = 0.729    if epoch == 2
>>> # lr = 0.6561   if epoch == 3
>>> # lr = 0.59049  if epoch >= 4
>>> scheduler1 = ConstantLR(optimizer, factor=0.1, total_iters=2)
>>> scheduler2 = ExponentialLR(optimizer, gamma=0.9)
>>> scheduler = ChainedScheduler([scheduler1, scheduler2], optimizer=optimizer)
>>> for epoch in range(100):
>>>     train(...)
>>>     validate(...)
>>>     scheduler.step()

get_last_lr()

Return last computed learning rate by current scheduler.

Return type

List[float]

get_lr()

Compute learning rate using chainable form of the scheduler.

Return type

List[float]

load_state_dict(state_dict)

Load the scheduler’s state.

Parameters

state_dict (dict) – scheduler state. Should be an object returned from a call to state_dict().

print_lr(is_verbose, group, lr, epoch=None)

Display the current learning rate.

Deprecated since version 2.4: print_lr() is deprecated. Please use get_last_lr() to access the learning rate.

state_dict()

Return the state of the scheduler as a dict.

It contains an entry for every variable in self.__dict__ which is not the optimizer. The wrapped scheduler states will also be saved.

step()

Perform a step.