Solved by god_sp33d in post #2 
              
              
                Hi, 
So, when you are doing x.unsqueeze(1), you are basically passing an input size as (8,1,20,20). Now, the output dimensions of your conv operation depends on the number of out_channels you pass in. 
so, let’s say you pass in out_channels=1, then you end up with an output size of (8,1,19,19). [19 …