Solved by KFrank in post #2 
              
              
                Hi Night! 

Roughly speaking, there is no difference. 

Note, as written, this won’t work.  This calls the MSELoss constructor 
with invalid arguments.  You need: 
loss_value = torch.nn.MSELoss() (input, target)
# or
loss_function = torch.nn.MSELoss()
loss_value = loss_function (input, target)

That…