---
id: pr-flash-attention-2549
repo: Dao-AILab/flash-attention
pr: 2549
title: '[Cute,Bwd,Sm100] fix incorrect calculation of n_block global max for bwd deterministic'
author: jayhshah
date: '2026-05-08'
url: https://github.com/Dao-AILab/flash-attention/pull/2549
source_category: upstream-code
architectures:
- sm100
tags:
- attention
- attention kernel
- cute
- sm100
techniques: []
hardware_features:
- blackwell
kernel_types:
- attention
languages:
- cuda-cpp
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: ab66326aaa4fe3529fbc00f3156f3a762dd3141b
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- flash_attn/cute/block_info.py
- flash_attn/cute/flash_bwd_sm100.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-2549
head_ref_oid: 8c69959dc104b2e6a36e75ee16bbc890ab483200
---
# [Cute,Bwd,Sm100] fix incorrect calculation of n_block global max for bwd deterministic

- Repository: `Dao-AILab/flash-attention`
- PR: [2549](https://github.com/Dao-AILab/flash-attention/pull/2549)
- Decision: `Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.`
- Reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.

## Changed Paths

- `flash_attn/cute/block_info.py`
- `flash_attn/cute/flash_bwd_sm100.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2549`
