Solved by KFrank in post #2 
              
              
                Hi Marc! 

Your understanding of groups does seem to be correct.  However, 
in your test you’ve overlooked Conv2d's bias. 
You can either turn bias off (bias = False) or copy bias over 
from conv1 to conv2, along with weight: 
>>> import torch
>>> import torch.nn as nn
>>>
>>> I = torch.randn(10,3,4…