optim_schedule.py

'''A wrapper class for optimizer '''
import numpy as np
from torch.optim.lr_scheduler import LambdaLR


class WarmupLinearSchedule(LambdaLR):
    """ Linear warmup and then linear decay.
        Linearly increases learning rate from 0 to 1 over `warmup_steps` training steps.
        Linearly decreases learning rate from 1. to 0. over remaining `t_total - warmup_steps`
        steps.
    """
    def __init__(self, optimizer, warmup_steps, t_total, last_epoch=-1):
        self.warmup_steps = warmup_steps
        self.t_total = t_total
        super(WarmupLinearSchedule, self).__init__(
            optimizer, self.lr_lambda, last_epoch=last_epoch)

    def lr_lambda(self, step):
        if step < self.warmup_steps:
            return float(step) / float(max(1, self.warmup_steps))
        return max(0.0, float(self.t_total - step) / float(
            max(1.0, self.t_total - self.warmup_steps)))