[GH-ISSUE #199] The comparison between cublaslt and deepgemm in test_fp8.py is unaligned #114

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opened 2026-10-26 21:12:53 +00:00 by bsakaguchi · 1 comment
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Originally created by @Insideyyy on GitHub (Sep 26, 2025).
Original GitHub issue: https://github.com/deepseek-ai/DeepGEMM/issues/199

It's great that PR #198 added cublas implementation to test_fp8.py, so we can directly observe the performance differences.
That said, I noticed the cublas implementation uses tensorwise scaling(cublas default behavior) instead of blockwise scaling, which makes the comparison with deepgemm less fair and potentially misleading.
Would it be possible to align the scaling strategy? I suppose cublas currently has supported the blockwise scaling strategy same with deepgemm: https://docs.nvidia.com/cuda/cublas/#element-1d-and-128x128-2d-block-scaling-for-fp8-data-types

Originally created by @Insideyyy on GitHub (Sep 26, 2025). Original GitHub issue: https://github.com/deepseek-ai/DeepGEMM/issues/199 It's great that PR #198 added cublas implementation to test_fp8.py, so we can directly observe the performance differences. That said, I noticed the cublas implementation uses tensorwise scaling(cublas default behavior) instead of blockwise scaling, which makes the comparison with deepgemm less fair and potentially misleading. Would it be possible to align the scaling strategy? I suppose cublas currently has supported the blockwise scaling strategy same with deepgemm: https://docs.nvidia.com/cuda/cublas/#element-1d-and-128x128-2d-block-scaling-for-fp8-data-types
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@zheanxu commented on GitHub (Apr 27, 2026):

Thanks for the detailed observation! This was intentional: we chose tensorwise scaling to keep the cuBLAS baseline simple and use it as a "no block scaling overhead" reference point for comparison.

<!-- gh-comment-id:4324492421 --> @zheanxu commented on GitHub (Apr 27, 2026): Thanks for the detailed observation! This was intentional: we chose tensorwise scaling to keep the cuBLAS baseline simple and use it as a "no block scaling overhead" reference point for comparison.
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deepseek-ai/DeepGEMM#114
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