"""
AdamP Optimizer Implementation copied from https://github.com/clovaai/AdamP/blob/master/adamp/adamp.py
Paper: `Slowing Down the Weight Norm Increase in Momentum-based Optimizers` - https://arxiv.org/abs/2006.08217
Code: https://github.com/clovaai/AdamP
Copyright (c) 2020-present NAVER Corp.
MIT license
"""
import torch
import torch.nn.functional as F
from torch.optim.optimizer import Optimizer
import math
def _channel_view(x) -> torch.Tensor:
return x.reshape(x.size(0), -1)
def _layer_view(x) -> torch.Tensor:
return x.reshape(1, -1)
def projection(p, grad, perturb, delta: float, wd_ratio: float, eps: float):
wd = 1.
expand_size = (-1,) + (1,) * (len(p.shape) - 1)
for view_func in [_channel_view, _layer_view]:
param_view = view_func(p)
grad_view = view_func(grad)
cosine_sim = F.cosine_similarity(grad_view, param_view, dim=1, eps=eps).abs_()
# FIXME this is a problem for PyTorch XLA
if cosine_sim.max() < delta / math.sqrt(param_view.size(1)):
p_n = p / param_view.norm(p=2, dim=1).add_(eps).reshape(expand_size)
perturb -= p_n * view_func(p_n * perturb).sum(dim=1).reshape(expand_size)
wd = wd_ratio
return perturb, wd
return perturb, wd
[docs]class AdamP(Optimizer):
def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-8,
weight_decay=0, delta=0.1, wd_ratio=0.1, nesterov=False):
defaults = dict(
lr=lr, betas=betas, eps=eps, weight_decay=weight_decay,
delta=delta, wd_ratio=wd_ratio, nesterov=nesterov)
super(AdamP, self).__init__(params, defaults)
[docs] @torch.no_grad()
def step(self, closure=None):
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
grad = p.grad
beta1, beta2 = group['betas']
nesterov = group['nesterov']
state = self.state[p]
# State initialization
if len(state) == 0:
state['step'] = 0
state['exp_avg'] = torch.zeros_like(p)
state['exp_avg_sq'] = torch.zeros_like(p)
# Adam
exp_avg, exp_avg_sq = state['exp_avg'], state['exp_avg_sq']
state['step'] += 1
bias_correction1 = 1 - beta1 ** state['step']
bias_correction2 = 1 - beta2 ** state['step']
exp_avg.mul_(beta1).add_(grad, alpha=1 - beta1)
exp_avg_sq.mul_(beta2).addcmul_(grad, grad, value=1 - beta2)
denom = (exp_avg_sq.sqrt() / math.sqrt(bias_correction2)).add_(group['eps'])
step_size = group['lr'] / bias_correction1
if nesterov:
perturb = (beta1 * exp_avg + (1 - beta1) * grad) / denom
else:
perturb = exp_avg / denom
# Projection
wd_ratio = 1.
if len(p.shape) > 1:
perturb, wd_ratio = projection(p, grad, perturb, group['delta'], group['wd_ratio'], group['eps'])
# Weight decay
if group['weight_decay'] > 0:
p.mul_(1. - group['lr'] * group['weight_decay'] * wd_ratio)
# Step
p.add_(perturb, alpha=-step_size)
return loss