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| '''A wrapper class for optimizer ''' | |
| import numpy as np | |
| class ScheduledOptim(): | |
| '''A simple wrapper class for learning rate scheduling''' | |
| def __init__(self, optimizer, d_model, n_warmup_steps): | |
| self._optimizer = optimizer | |
| self.n_warmup_steps = n_warmup_steps | |
| self.n_current_steps = 0 | |
| self.init_lr = np.power(d_model, -0.5) | |
| def step_and_update_lr(self): | |
| "Step with the inner optimizer" | |
| self._update_learning_rate() | |
| self._optimizer.step() | |
| def zero_grad(self): | |
| "Zero out the gradients by the inner optimizer" | |
| self._optimizer.zero_grad() | |
| def _get_lr_scale(self): | |
| return np.min([ | |
| np.power(self.n_current_steps, -0.5), | |
| np.power(self.n_warmup_steps, -1.5) * self.n_current_steps]) | |
| def _update_learning_rate(self): | |
| ''' Learning rate scheduling per step ''' | |
| self.n_current_steps += 1 | |
| lr = self.init_lr * self._get_lr_scale() | |
| for param_group in self._optimizer.param_groups: | |
| param_group['lr'] = lr | |