NVIDIA / NVIDIA/cutlass

[QST]What does Epilogue do?(Especially in Hopper)

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Description

I am writing example 48, and I noticed file:
https://github.com/NVIDIA/cutlass/blob/06b21349bcf6ddf6a1686a47a137ad1446579db9/include/cutlass/gemm/kernel/sm90_gemm_tma_warpspecialized_cooperative.hpp#L321
I find out with surprise that, epilogue is in producer, but we do not even enter epilogue?! Previously I guess we save result using epilogue, both rearrange it into shared memory and then save into global, but now, storing is done in cousumer...?

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Research direction

Start with include/cutlass/gemm/kernel/sm90_gemm_tma_warpspecialized_cooperative.hpp around line 321 and compare it with the context of example 48. Trace how the producer, consumer, and epilogue roles relate to storing results in Hopper. Done means providing a clear explanation of what the epilogue does and why the observed execution path places storing in the consumer.

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Assessment

Tech stack
cpp
Domain
hpc, performance
Issue type
Documentation
Difficulty
4/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
35/100

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