# Week 1 Assignment 1, conv_forward()

Hi,
I am getting an error “Wrong output for variable in position 0”, and above that is this line (2, 13, 15, 8), which I am assuming is the shape of `A_prev` but I am not sure, and I don’t understand why it is being printed lol. And I can’t for the life of me figure out what I am doing wrong. I would post the code I wrote here but I am not sure if that would be okay with Coursera’s Honor code. All the shapes seem to be fine, no syntax errors of course, since the code is running. I checked all the things suggested in the additional hints, it seems all good. So I would really appreciate any guidance/pointers, and if I am allowed to post my code, please do that, I’ll post it.

The tricky bits in this function seem to be:

• how you compute the start and end values for the horizontal and vertical dimensions. The start values should include a multiplication by “stride”.
• you also have to slice W and b correctly.
• and use the correct ranges for all three for-loops.
3 Likes

Thank you so much, that helped. I was using `range(0, n_W, stride)` and similarly for `n_H`, so I was ending up skipping some values of h and w entirely, which meant that Z wasn’t being computed at all indices.

The start values should include a multiplication by “stride”

That solved it of course.

Hey,

So the below code would be incorrect?

for h in range(0, n_H, stride):
vert_start = h
vert_end = h + f

Looks like, I also had the same issue as him, and I was using the same code as you said. Just changed to range(n_W) and use multiplication by stride in the start values. That solved all.