Solved by pfloat in post #2 
              
              
                hello 
try this: 
b = torch.rand(64, 10)
a = torch.rand(64, 40) 
torch.cat([a, b], dim=1) # shape is torch.Size([64, 50])

you can have more details in these posts: 
how-to-concatenate-list-of-pytorch-tensors 
tensor-stack-or-concatenate