File size: 5,502 Bytes
3ad86c5 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 |
""" AdamW Optimizer
Impl copied from PyTorch master
NOTE: This impl has been deprecated in favour of torch.optim.AdamW and remains as a reference
"""
import math
from typing import Tuple
import torch
from torch.optim.optimizer import Optimizer
from ._types import ParamsT
class AdamWLegacy(Optimizer):
r"""Implements AdamW algorithm.
NOTE: This impl has been deprecated in favour of torch.optim.NAdam and remains as a reference
References:
- Adam: A Method for Stochastic Optimization: https://arxiv.org/abs/1412.6980
- Decoupled Weight Decay Regularization: https://arxiv.org/abs/1711.05101
- On the Convergence of Adam and Beyond: https://openreview.net/forum?id=ryQu7f-RZ
Args:
params: iterable of parameters to optimize or dicts defining parameter groups
lr: learning rate
betas: coefficients used for computing running averages of gradient and its square
eps: term added to the denominator to improve numerical stability
weight_decay: weight decay coefficient
amsgrad: whether to use the AMSGrad variant of this algorithm
from the paper `On the Convergence of Adam and Beyond`
caution: apply caution when using AdamW
"""
def __init__(
self,
params: ParamsT,
lr: float = 1e-3,
betas: Tuple[float, float] = (0.9, 0.999),
eps: float = 1e-8,
weight_decay: float = 1e-2,
amsgrad: bool = False,
caution: bool = False,
):
if not 0.0 <= lr:
raise ValueError("Invalid learning rate: {}".format(lr))
if not 0.0 <= eps:
raise ValueError("Invalid epsilon value: {}".format(eps))
if not 0.0 <= betas[0] < 1.0:
raise ValueError("Invalid beta parameter at index 0: {}".format(betas[0]))
if not 0.0 <= betas[1] < 1.0:
raise ValueError("Invalid beta parameter at index 1: {}".format(betas[1]))
defaults = dict(
lr=lr,
betas=betas,
eps=eps,
weight_decay=weight_decay,
amsgrad=amsgrad,
caution=caution,
)
super(AdamWLegacy, self).__init__(params, defaults)
def __setstate__(self, state):
super(AdamWLegacy, self).__setstate__(state)
for group in self.param_groups:
group.setdefault('amsgrad', False)
group.setdefault('caution', False)
@torch.no_grad()
def step(self, closure=None):
"""Performs a single optimization step.
Arguments:
closure (callable, optional): A closure that reevaluates the model
and returns the loss.
"""
loss = None
if closure is not None:
with torch.enable_grad():
loss = closure()
for group in self.param_groups:
for p in group['params']:
if p.grad is None:
continue
# Perform stepweight decay
p.data.mul_(1 - group['lr'] * group['weight_decay'])
# Perform optimization step
grad = p.grad
if grad.is_sparse:
raise RuntimeError('Adam does not support sparse gradients, please consider SparseAdam instead')
amsgrad = group['amsgrad']
state = self.state[p]
# State initialization
if len(state) == 0:
state['step'] = 0
# Exponential moving average of gradient values
state['exp_avg'] = torch.zeros_like(p)
# Exponential moving average of squared gradient values
state['exp_avg_sq'] = torch.zeros_like(p)
if amsgrad:
# Maintains max of all exp. moving avg. of sq. grad. values
state['max_exp_avg_sq'] = torch.zeros_like(p)
exp_avg, exp_avg_sq = state['exp_avg'], state['exp_avg_sq']
if amsgrad:
max_exp_avg_sq = state['max_exp_avg_sq']
beta1, beta2 = group['betas']
state['step'] += 1
bias_correction1 = 1 - beta1 ** state['step']
bias_correction2 = 1 - beta2 ** state['step']
# Decay the first and second moment running average coefficient
exp_avg.mul_(beta1).add_(grad, alpha=1 - beta1)
exp_avg_sq.mul_(beta2).addcmul_(grad, grad, value=1 - beta2)
if amsgrad:
# Maintains the maximum of all 2nd moment running avg. till now
torch.max(max_exp_avg_sq, exp_avg_sq, out=max_exp_avg_sq)
# Use the max. for normalizing running avg. of gradient
denom = (max_exp_avg_sq.sqrt() / math.sqrt(bias_correction2)).add_(group['eps'])
else:
denom = (exp_avg_sq.sqrt() / math.sqrt(bias_correction2)).add_(group['eps'])
step_size = group['lr'] / bias_correction1
if group['caution']:
# Apply caution as per 'Cautious Optimizers' - https://arxiv.org/abs/2411.16085
mask = (exp_avg * grad > 0).to(grad.dtype)
mask.div_(mask.mean().clamp_(min=1e-3))
exp_avg = exp_avg * mask
p.addcdiv_(exp_avg, denom, value=-step_size)
return loss
|