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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 math |
| | | |
| | | import torch |
| | | import torch.optim |
| | | |
| | | |
| | | class FairseqAdam(torch.optim.Optimizer): |
| | | r"""Implements Adam algorithm. |
| | | |
| | | This implementation is modified from torch.optim.Adam based on: |
| | | `Fixed Weight Decay Regularization in Adam` |
| | | (see https://arxiv.org/abs/1711.05101) |
| | | |
| | | It has been proposed in `Adam: A Method for Stochastic Optimization`_. |
| | | |
| | | Args: |
| | | params (iterable): iterable of parameters to optimize or dicts defining |
| | | parameter groups |
| | | lr (float, optional): learning rate (default: 1e-3) |
| | | betas (Tuple[float, float], optional): coefficients used for computing |
| | | running averages of gradient and its square (default: (0.9, 0.999)) |
| | | eps (float, optional): term added to the denominator to improve |
| | | numerical stability (default: 1e-8) |
| | | weight_decay (float, optional): weight decay (L2 penalty) (default: 0) |
| | | amsgrad (boolean, optional): whether to use the AMSGrad variant of this |
| | | algorithm from the paper `On the Convergence of Adam and Beyond`_ |
| | | |
| | | .. _Adam\: A Method for Stochastic Optimization: |
| | | https://arxiv.org/abs/1412.6980 |
| | | .. _On the Convergence of Adam and Beyond: |
| | | https://openreview.net/forum?id=ryQu7f-RZ |
| | | """ |
| | | |
| | | def __init__( |
| | | self, |
| | | params, |
| | | lr=1e-3, |
| | | adam_betas=(0.9, 0.999), |
| | | adam_eps=1e-8, |
| | | weight_decay=0, |
| | | amsgrad=False, |
| | | ): |
| | | defaults = dict( |
| | | lr=lr, betas=adam_betas, eps=adam_eps, weight_decay=weight_decay, amsgrad=amsgrad |
| | | ) |
| | | super(FairseqAdam, self).__init__(params, defaults) |
| | | self.optimizer_lr = lr |
| | | |
| | | @property |
| | | def supports_memory_efficient_fp16(self): |
| | | return True |
| | | |
| | | @property |
| | | def supports_flat_params(self): |
| | | return True |
| | | |
| | | def step(self, closure=None): |
| | | """Performs a single optimization step. |
| | | |
| | | Args: |
| | | closure (callable, optional): A closure that reevaluates the model |
| | | and returns the loss. |
| | | """ |
| | | 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 |
| | | if grad.dtype in {torch.float16, torch.bfloat16}: |
| | | grad = grad.float() |
| | | if grad.is_sparse: |
| | | raise RuntimeError( |
| | | "Adam does not support sparse gradients, please consider SparseAdam instead" |
| | | ) |
| | | amsgrad = group.get("amsgrad", False) |
| | | |
| | | p_data_fp32 = p.data |
| | | if p.data.dtype in {torch.float16, torch.bfloat16}: |
| | | p_data_fp32 = p_data_fp32.float() |
| | | |
| | | 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_data_fp32) |
| | | # Exponential moving average of squared gradient values |
| | | state["exp_avg_sq"] = torch.zeros_like(p_data_fp32) |
| | | if amsgrad: |
| | | # Maintains max of all exp. moving avg. of sq. grad. values |
| | | state["max_exp_avg_sq"] = torch.zeros_like(p_data_fp32) |
| | | else: |
| | | state["exp_avg"] = state["exp_avg"].to(p_data_fp32) |
| | | state["exp_avg_sq"] = state["exp_avg_sq"].to(p_data_fp32) |
| | | if amsgrad: |
| | | state["max_exp_avg_sq"] = state["max_exp_avg_sq"].to( |
| | | p_data_fp32 |
| | | ) |
| | | |
| | | 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 |
| | | |
| | | # 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().add_(group["eps"]) |
| | | else: |
| | | denom = exp_avg_sq.sqrt().add_(group["eps"]) |
| | | |
| | | bias_correction1 = 1 - beta1 ** state["step"] |
| | | bias_correction2 = 1 - beta2 ** state["step"] |
| | | step_size = group["lr"] * math.sqrt(bias_correction2) / bias_correction1 |
| | | |
| | | if group["weight_decay"] != 0: |
| | | p_data_fp32.add_( |
| | | p_data_fp32, alpha=-group["weight_decay"] * group["lr"] |
| | | ) |
| | | |
| | | p_data_fp32.addcdiv_(exp_avg, denom, value=-step_size) |
| | | |
| | | if p.data.dtype in {torch.float16, torch.bfloat16}: |
| | | p.data.copy_(p_data_fp32) |
| | | |
| | | return loss |
| | | |
| | | def set_lr(self, lr): |
| | | """Set the learning rate.""" |
| | | for param_group in self.param_groups: |
| | | param_group["lr"] = lr |