Hi all,
I faced a backward problem.
Let’s say there are two Variables x, y, which are calculated by some other functions.
And we have that
z = x * mask + y * (1 - mask),
when mask = 1, we have that z = x * 1 + y * 0. When we do z.backward(), I find that y.grad is 0 instead of None, which means that the backpropagate pass through Variable y.  This makes the backward slow.
I wonder that is it possible to prevent the backward pass through y in the above case?
Thank you very much!