Solved by ptrblck in post #4 
              
              
                3 groups with a filter using in_channels=3 would need 9 channels. 
The grouped conv section or the docs give you more information on the usage of the groups argument. 
If you want to process each input channel separately, use: 
input = torch.rand(4, 3, 8, 8)
weight = torch.ones(3, 1, 3, 3)
out = tor…