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Support dense THD stats graphs on SM8x - #5

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Support dense THD stats graphs on SM8x#5
sudhakarsingh27 wants to merge 2 commits into
cyanguwa:fe_check_supportfrom
sudhakarsingh27:sudhakars/sm8x-thd-graph-support

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@sudhakarsingh27 sudhakarsingh27 commented Jul 29, 2026

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Summary

  • use one internal predicate for packed-ragged graph dimensions and Stats/LSE
  • keep SM8x and SM120 on dense B x H x S_q x 1 Stats/Max tensors and max-sequence graph dimensions
  • align graph-cache normalization with the representation actually built
  • apply backend-independent THD padding filters to mixed Q/KV layouts

Why

cuDNN 9.18.1 enables THD inputs on SM8x, but packed/ragged LSE remains unsupported for backward propagation there. The PR 2964 graph-as-the-source-of-truth approach is reliable only when the probed graph uses the runtime-supported representation. Its cache key must normalize the same dimensions that graph construction uses.

This intentionally does not add a separate hard-coded SM8x/cuDNN fused-support table: the forward and backward graph probes remain authoritative.

Validation

  • all repository pre-commit hooks passed before publication
  • Python 3.12 byte-compilation passed for the modified Python source
  • git diff --check passed
  • C++ and SM8x/cuDNN runtime validation was not run locally because this workstation has neither a CUDA compiler nor a built Transformer Engine

cuDNN accepts THD on SM8x from 9.18.1 but requires dense Stats/LSE and max-sequence graph dimensions there. Use one representation predicate for graph construction, auxiliary allocation, and cache-key normalization so support probing and execution cannot diverge.

Broaden the shared Python THD layout filter to mixed Q/KV layouts and add focused predicate, padding-filter, and SM8x support-boundary coverage.

Signed-off-by: Sudhakar Singh <sudhakars@nvidia.com>
Keep the cross-fork follow-up limited to the requested production-code changes.

Signed-off-by: Sudhakar Singh <sudhakars@nvidia.com>
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