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# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import torch
from fairseq import utils
class FairseqOptimizer(object):
def __init__(self, args):
super().__init__()
self.args = args
@staticmethod
def add_args(parser):
"""Add optimizer-specific arguments to the parser."""
pass
@property
def optimizer(self):
"""Return a torch.optim.optimizer.Optimizer instance."""
if not hasattr(self, '_optimizer'):
raise NotImplementedError
if not isinstance(self._optimizer, torch.optim.Optimizer):
raise ValueError('_optimizer must be an instance of torch.optim.Optimizer')
return self._optimizer
@property
def optimizer_config(self):
"""
Return a kwarg dictionary that will be used to override optimizer
args stored in checkpoints. This allows us to load a checkpoint and
resume training using a different set of optimizer args, e.g., with a
different learning rate.
"""
raise NotImplementedError
@property
def params(self):
"""Return an iterable of the parameters held by the optimizer."""
for param_group in self.param_groups:
for p in param_group['params']:
yield p
@property
def param_groups(self):
return self.optimizer.param_groups
def __getstate__(self):
return self._optimizer.__getstate__()
def get_lr(self):
"""Return the current learning rate."""
return self.param_groups[0]['lr']
def set_lr(self, lr):
"""Set the learning rate."""
for param_group in self.param_groups:
param_group['lr'] = lr
def state_dict(self):
"""Return the optimizer's state dict."""
return self.optimizer.state_dict()
def load_state_dict(self, state_dict, optimizer_overrides=None):
"""Load an optimizer state dict.
In general we should prefer the configuration of the existing optimizer
instance (e.g., learning rate) over that found in the state_dict. This
allows us to resume training from a checkpoint using a new set of
optimizer args.
"""
self.optimizer.load_state_dict(state_dict)
if optimizer_overrides is not None and len(optimizer_overrides) > 0:
# override learning rate, momentum, etc. with latest values
for group in self.param_groups:
group.update(optimizer_overrides)
def backward(self, loss):
"""Computes the sum of gradients of the given tensor w.r.t. graph leaves."""
loss.backward()
def multiply_grads(self, c):
"""Multiplies grads by a constant *c*."""
for p in self.params:
if p.grad is not None:
p.grad.data.mul_(c)
def clip_grad_norm(self, max_norm, aggregate_norm_fn=None):
"""Clips gradient norm."""
return utils.clip_grad_norm_(self.params, max_norm, aggregate_norm_fn)
def step(self, closure=None, scale=1.):
"""Performs a single optimization step."""
if self.supports_step_with_scale:
self.optimizer.step(closure, scale=scale)
else:
self.optimizer.step(closure)
def zero_grad(self):
"""Clears the gradients of all optimized parameters."""
for p in self.params:
p.grad = None
self.optimizer.zero_grad()
@property
def supports_memory_efficient_fp16(self):
if hasattr(self.optimizer, 'supports_memory_efficient_fp16'):
return self.optimizer.supports_memory_efficient_fp16
return False
@property
def supports_step_with_scale(self):
if hasattr(self.optimizer, 'supports_step_with_scale'):
return self.optimizer.supports_step_with_scale
return False
@property
def supports_flat_params(self):
"""
Whether the optimizer supports collapsing of the model
parameters/gradients into a single contiguous Tensor.
"""
if hasattr(self.optimizer, 'supports_flat_params'):
return self.optimizer.supports_flat_params
return False
def average_params(self):
pass
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