muh-bot 0caabf285b fix(critical): v2 kernel softmax normalization was commented out — outputs were wrong
qwen3_6_scripts/prefix_prefill.py line 435:
  BEFORE: # acc /= l_i[:, None]  (commented out = BUG)
  AFTER:  acc = acc / l_i[:, None]  (restored)

Impact: _fwd_kernel_flash_attn_v2 was producing unnormalized attention
output — every prefill with context length > BLOCK_M would have had
incorrect softmax weights, causing wrong generation quality. This
directly affects the effect test (偏差 ≤ ±4% benchmark).

Root cause: the v1 kernel (_fwd_kernel) does online normalization
(p_scale = beta/l_i_new), but v2 uses acc_scale = alpha only and
defers normalization to the end. Someone commented out the final
division, breaking v2.

NOTE: The file that actually gets deployed is qwen3_6_scripts/,
NOT vllm/. Previous commits edited vllm/ which has no effect
on the built Docker image.
2026-08-07 02:46:46 +00:00
2026-07-30 17:03:23 +08:00

project_6

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