106 lines
4.5 KiB
Python
106 lines
4.5 KiB
Python
# modified from https://github.com/LiyuanLucasLiu/RAdam
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import math
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import torch
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from torch.optim.optimizer import Optimizer
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class RAdam(Optimizer):
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def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-8, weight_decay=0, degenerated_to_sgd=True):
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if lr < 0.0:
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raise ValueError("Invalid learning rate: {}".format(lr))
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if eps < 0.0:
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raise ValueError("Invalid epsilon value: {}".format(eps))
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if not 0.0 <= betas[0] < 1.0:
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raise ValueError("Invalid beta parameter at index 0: {}".format(betas[0]))
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if not 0.0 <= betas[1] < 1.0:
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raise ValueError("Invalid beta parameter at index 1: {}".format(betas[1]))
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self.degenerated_to_sgd = degenerated_to_sgd
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if isinstance(params, (list, tuple)) and len(params) > 0 and isinstance(params[0], dict):
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for param in params:
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if "betas" in param and (param["betas"][0] != betas[0] or param["betas"][1] != betas[1]):
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param["buffer"] = [[None, None, None] for _ in range(10)]
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defaults = dict(
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lr=lr, betas=betas, eps=eps, weight_decay=weight_decay, buffer=[[None, None, None] for _ in range(10)]
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)
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super().__init__(params, defaults)
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def __setstate__(self, state): # pylint: disable=useless-super-delegation
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super().__setstate__(state)
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def step(self, closure=None):
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loss = None
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if closure is not None:
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loss = closure()
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for group in self.param_groups:
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for p in group["params"]:
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if p.grad is None:
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continue
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grad = p.grad.data.float()
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if grad.is_sparse:
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raise RuntimeError("RAdam does not support sparse gradients")
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p_data_fp32 = p.data.float()
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state = self.state[p]
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if len(state) == 0:
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state["step"] = 0
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state["exp_avg"] = torch.zeros_like(p_data_fp32)
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state["exp_avg_sq"] = torch.zeros_like(p_data_fp32)
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else:
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state["exp_avg"] = state["exp_avg"].type_as(p_data_fp32)
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state["exp_avg_sq"] = state["exp_avg_sq"].type_as(p_data_fp32)
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exp_avg, exp_avg_sq = state["exp_avg"], state["exp_avg_sq"]
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beta1, beta2 = group["betas"]
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exp_avg_sq.mul_(beta2).addcmul_(grad, grad, value=1 - beta2)
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exp_avg.mul_(beta1).add_(grad, alpha=1 - beta1)
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state["step"] += 1
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buffered = group["buffer"][int(state["step"] % 10)]
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if state["step"] == buffered[0]:
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N_sma, step_size = buffered[1], buffered[2]
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else:
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buffered[0] = state["step"]
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beta2_t = beta2 ** state["step"]
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N_sma_max = 2 / (1 - beta2) - 1
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N_sma = N_sma_max - 2 * state["step"] * beta2_t / (1 - beta2_t)
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buffered[1] = N_sma
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# more conservative since it's an approximated value
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if N_sma >= 5:
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step_size = math.sqrt(
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(1 - beta2_t)
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* (N_sma - 4)
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/ (N_sma_max - 4)
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* (N_sma - 2)
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/ N_sma
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* N_sma_max
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/ (N_sma_max - 2)
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) / (1 - beta1 ** state["step"])
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elif self.degenerated_to_sgd:
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step_size = 1.0 / (1 - beta1 ** state["step"])
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else:
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step_size = -1
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buffered[2] = step_size
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# more conservative since it's an approximated value
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if N_sma >= 5:
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if group["weight_decay"] != 0:
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p_data_fp32.add_(p_data_fp32, alpha=-group["weight_decay"] * group["lr"])
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denom = exp_avg_sq.sqrt().add_(group["eps"])
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p_data_fp32.addcdiv_(exp_avg, denom, value=-step_size * group["lr"])
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p.data.copy_(p_data_fp32)
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elif step_size > 0:
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if group["weight_decay"] != 0:
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p_data_fp32.add_(p_data_fp32, alpha=-group["weight_decay"] * group["lr"])
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p_data_fp32.add_(exp_avg, alpha=-step_size * group["lr"])
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p.data.copy_(p_data_fp32)
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return loss
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