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| from torch.optim.lr_scheduler import _LRScheduler | |
| # This is rather suboptimal, because we need to import a protected class. Unfortunately, I don't see another way. | |
| class ToucanWarmupScheduler(_LRScheduler): | |
| """ | |
| A warmup scheduler that should be called after every batch. | |
| """ | |
| def __init__(self, optimizer, peak_lr=0.0002, warmup_steps=20000, max_steps=200000, last_epoch=-1): | |
| self.warmup_steps = warmup_steps | |
| self.peak_lr = peak_lr | |
| self.max_steps = max_steps | |
| self.plateau = self.warmup_steps * 4 | |
| self.last_lr = 0.0 | |
| # __init__() must be invoked before setting field | |
| # because step() is also invoked in __init__() | |
| super().__init__(optimizer, last_epoch) | |
| def __repr__(self): | |
| return f"{self.__class__.__name__}(warmup_steps={self.warmup_steps})" | |
| def get_lr(self): | |
| step_num = self.last_epoch + 1 | |
| if step_num <= self.warmup_steps: | |
| lr = self.peak_lr * min(step_num / self.warmup_steps, 1.0) | |
| self.last_lr = lr | |
| return [lr for _ in self.base_lrs] | |
| elif step_num < self.warmup_steps + self.plateau: | |
| self.last_lr = self.peak_lr | |
| return [self.peak_lr for _ in self.base_lrs] | |
| else: | |
| scale = 1 - (((step_num - (self.warmup_steps + self.plateau)) / self.max_steps) / (self.max_steps / 10)) | |
| self.last_lr = max(self.last_lr * scale, 1e-7) | |
| return [self.last_lr for _ in self.base_lrs] | |
| class WarmupScheduler(_LRScheduler): | |
| """ | |
| The WarmupLR scheduler | |
| This scheduler is almost same as NoamLR Scheduler except for following difference: | |
| NoamLR: | |
| lr = optimizer.lr * model_size ** -0.5 | |
| * min(step ** -0.5, step * warmup_step ** -1.5) | |
| WarmupLR: | |
| lr = optimizer.lr * warmup_step ** 0.5 | |
| * min(step ** -0.5, step * warmup_step ** -1.5) | |
| Note that the maximum lr equals to optimizer.lr in this scheduler. | |
| Taken from ESPnet | |
| """ | |
| def __init__(self, optimizer, warmup_steps=25000, last_epoch=-1): | |
| self.warmup_steps = warmup_steps | |
| # __init__() must be invoked before setting field | |
| # because step() is also invoked in __init__() | |
| super().__init__(optimizer, last_epoch) | |
| def __repr__(self): | |
| return f"{self.__class__.__name__}(warmup_steps={self.warmup_steps})" | |
| def get_lr(self): | |
| step_num = self.last_epoch + 1 | |
| return [lr * self.warmup_steps ** 0.5 * min(step_num ** -0.5, step_num * self.warmup_steps ** -1.5) for lr in | |
| self.base_lrs] | |
| if __name__ == '__main__': | |
| lrs = list() | |
| warmup_steps = 30000 | |
| peak_lr = 0.0005 | |
| max_steps = 800000 | |
| plateau_size = warmup_steps * 5 | |
| for step_num in range(max_steps): | |
| if step_num <= warmup_steps: | |
| lr = peak_lr * min(step_num / warmup_steps, 1.0) | |
| lrs.append(lr) | |
| elif step_num < warmup_steps + plateau_size: | |
| lrs.append(peak_lr) | |
| else: | |
| scale = 1 - (((step_num - (warmup_steps + plateau_size)) / max_steps) / (max_steps / 10)) | |
| lrs.append(max(lrs[-1] * scale, 1e-7)) | |
| import matplotlib.pyplot as plt | |
| plt.plot(lrs) | |
| plt.show() | |