http://www.sohu.com/a/336981343_500659
加速三部曲：PyTorch实现
1 ：
from apex importamp
2:
model, optimizer = amp.initialize(model, optimizer, opt_level= "O1") # 这里是“欧一”，不是“零一”
3:
with amp.scale_loss(loss, optimizer) as scaled_loss:
scaled_loss.backward()
