Solved by dazzle-me in post #2 
              
              
                Sure. 
I guess your x tensor has a shape of length 2. 
In torch,  dim = -1 means that the operation has to be performed along last dimension, and I think that is why   torch.cat((x, x, x,) -1) == torch.cat((x, x, x,), 1) 
(not strictly because it’s links and something but you got the idea)  in your …