[QST] Questions about correctness test and layout

[haeunlee99]

Hello, I have several question using CUTLASS. It would be very much appreciated to be answered.

1. How to know if I am calling CUTLASS code correctly?
   I am using matrix A (M x K), matrix B (N x K), matrix C (M x N) and calling cutlass call like below. I transposed B and provided A, B^T and C as argument, which aligns with the layout in the picture. Each A, B, C are half precision, and accumulator is fp32.

I am also calling CUBLAS kernel, but this time providing A and B, making kernel transpose by itself.

When I compare the result for M = N = K = 4096, I see maximum error of 0.25, which seems to be above 0.05 default value given for CUTLASS profiler. I wonder whether changes in instruction shape, warp size or thread block size affects error value. I am using shapes like this picture.

Should I be getting 0 error to know whether I am calling the same kernel with same layout setting?
What is epilson and non-zero floor in this function used by CUTLASS profiler?

2. What is the correlation between thread block shape, warp shape and instruction shape?
   If I use any of the warp shapes given in documentation of picture below, it gives me error in the second picture.
   Thus, none of the warp shapes I can use to directly use to call GemmUniversal.

Thanks in advance!

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This issue has been labeled inactive-90d due to no recent activity in the past 90 days. Please close this issue if no further response or action is needed. Otherwise, please respond with a comment indicating any updates or changes to the original issue and/or confirm this issue still needs to be addressed.