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Fix: disable 2-CTA backward mode when block_sparse_tensors is used #2433

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Merged
drisspg merged 1 commit into from
Apr 3, 2026
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Fix: disable 2-CTA backward mode when block_sparse_tensors is used #2433

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1 change: 1 addition & 0 deletions flash_attn/cute/interface.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1086,6 +1086,7 @@ def _flash_attn_bwd(
or score_mod is not None
or score_mod_bwd is not None
or mask_mod is not None
or block_sparse_tensors is not None
)
cluster_size = 2 if head_dim >= 128 and not disable_2cta else 1
use_2cta_instrs = cluster_size==2
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