Week 1, assignment 1: error in grading? optional backprop exercise counted?

I got ‘all tests passed’ on every graded portion of the first assignment in week 1, course 4 on CNNs. But yet I only received 50% as my grade? There is an optional portion of the assignment on backpropagation of CNNs. Is the grader trying to grade the optional portion too, resulting in my failing grade?

No, it’s not the optional part causing a problem.
The unit tests for this assignment do not catch some very common errors.

Usually it has to do with how you are using the “stride” variable in conv forward and pooling forward. The key problem happens when stride = 2. But the unit tests do not catch many potential errors.

If you are using “stride” within a for-loop “range()” iterator, that’s the problem.

Thanks, I got it now! And good to know that the grading isn’t defective for this assignment.