torch 赋值运行效率

尽量少进行赋值，一模一样的操作，赋值竟然慢了一倍

import torch
import time
x=torch.rand(9,256,40,40)
t=100
st=time.time()
for i in range(t):
    z=torch.clamp(x+3,0,1)
ed=time.time()
print(ed-st)
st=time.time()
for i in range(t):
    z=x+3
    z=torch.clamp(z,0,1)
ed=time.time()
print(ed-st)

0.3989396095275879
0.2272486686706543