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| # -*- coding: utf-8 -*- | |
| """RAdam optimizer. | |
| This code is drived from https://github.com/LiyuanLucasLiu/RAdam. | |
| """ | |
| import math | |
| import torch | |
| from torch.optim.optimizer import Optimizer | |
| class RAdam(Optimizer): | |
| """Rectified Adam optimizer.""" | |
| def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-8, weight_decay=0): | |
| """Initilize RAdam optimizer.""" | |
| defaults = dict(lr=lr, betas=betas, eps=eps, weight_decay=weight_decay) | |
| self.buffer = [[None, None, None] for ind in range(10)] | |
| super(RAdam, self).__init__(params, defaults) | |
| def __setstate__(self, state): | |
| """Set state.""" | |
| super(RAdam, self).__setstate__(state) | |
| def step(self, closure=None): | |
| """Run one step.""" | |
| loss = None | |
| if closure is not None: | |
| loss = closure() | |
| for group in self.param_groups: | |
| for p in group['params']: | |
| if p.grad is None: | |
| continue | |
| grad = p.grad.data.float() | |
| if grad.is_sparse: | |
| raise RuntimeError('RAdam does not support sparse gradients') | |
| p_data_fp32 = p.data.float() | |
| state = self.state[p] | |
| if len(state) == 0: | |
| state['step'] = 0 | |
| state['exp_avg'] = torch.zeros_like(p_data_fp32) | |
| state['exp_avg_sq'] = torch.zeros_like(p_data_fp32) | |
| else: | |
| state['exp_avg'] = state['exp_avg'].type_as(p_data_fp32) | |
| state['exp_avg_sq'] = state['exp_avg_sq'].type_as(p_data_fp32) | |
| exp_avg, exp_avg_sq = state['exp_avg'], state['exp_avg_sq'] | |
| beta1, beta2 = group['betas'] | |
| exp_avg_sq.mul_(beta2).addcmul_(1 - beta2, grad, grad) | |
| exp_avg.mul_(beta1).add_(1 - beta1, grad) | |
| state['step'] += 1 | |
| buffered = self.buffer[int(state['step'] % 10)] | |
| if state['step'] == buffered[0]: | |
| N_sma, step_size = buffered[1], buffered[2] | |
| else: | |
| buffered[0] = state['step'] | |
| beta2_t = beta2 ** state['step'] | |
| N_sma_max = 2 / (1 - beta2) - 1 | |
| N_sma = N_sma_max - 2 * state['step'] * beta2_t / (1 - beta2_t) | |
| buffered[1] = N_sma | |
| # more conservative since it's an approximated value | |
| if N_sma >= 5: | |
| step_size = math.sqrt( | |
| (1 - beta2_t) * (N_sma - 4) / (N_sma_max - 4) * (N_sma - 2) / N_sma * N_sma_max / (N_sma_max - 2)) / (1 - beta1 ** state['step']) # NOQA | |
| else: | |
| step_size = 1.0 / (1 - beta1 ** state['step']) | |
| buffered[2] = step_size | |
| if group['weight_decay'] != 0: | |
| p_data_fp32.add_(-group['weight_decay'] * group['lr'], p_data_fp32) | |
| # more conservative since it's an approximated value | |
| if N_sma >= 5: | |
| denom = exp_avg_sq.sqrt().add_(group['eps']) | |
| p_data_fp32.addcdiv_(-step_size * group['lr'], exp_avg, denom) | |
| else: | |
| p_data_fp32.add_(-step_size * group['lr'], exp_avg) | |
| p.data.copy_(p_data_fp32) | |
| return loss | |