Fix flash attention for non-pow2 dims, large dims, and backward NaN#7
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Fix flash attention for non-pow2 dims, large dims, and backward NaN#7
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murrellb
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Feb 18, 2026
murrellb
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- Support non-pow2 emb_dim via kernel-level zero-padding (padded_dim)
- Add smaller groupsizes (8, 4) for large dims exceeding 48KB shmem
- Clamp MMA tile sizes (TM ≤ BM, TN ≤ BN) to prevent OOB shmem access
- Fix backward NaN: mask OOB K positions in softmax reconstruction to prevent exp(0-m_i)→Inf then Inf*0→NaN contaminating dQ
- Guard preprocess inv(ls) against ls=0 division
- Support non-pow2 emb_dim via kernel-level zero-padding (padded_dim) - Add smaller groupsizes (8, 4) for large dims exceeding 48KB shmem - Clamp MMA tile sizes (TM ≤ BM, TN ≤ BN) to prevent OOB shmem access - Fix backward NaN: mask OOB K positions in softmax reconstruction to prevent exp(0-m_i)→Inf then Inf*0→NaN contaminating dQ - Guard preprocess inv(ls) against ls=0 division Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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