在pytorch中设置learning rate的衰减

很多时候我们要对学习率（learning rate）进行衰减，下面的代码示范了如何每30个epoch按10%的速率衰减：

def adjust_learning_rate(optimizer, epoch):
    """Sets the learning rate to the initial LR decayed by 10 every 30 epochs"""
    lr = args.lr * (0.1 ** (epoch // 30))
    for param_group in optimizer.param_groups:
        param_group['lr'] = lr

来源：https://www.pytorchtutorial.com/pytorch-learning-rate-decay/