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@Isotr0py Isotr0py commented Aug 28, 2025

Purpose

cc @HelloZhang525, can you check if this PR can solve the accuracy issue at TP=4? I only have 2 T4 GPU to investigate this.

Test Plan

Test Result


Essential Elements of an Effective PR Description Checklist
  • The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
  • The test plan, such as providing test command.
  • The test results, such as pasting the results comparison before and after, or e2e results
  • (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
  • (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>
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Code Review

This pull request fixes an accuracy issue with sequence classification models when using tensor parallelism. The change replaces RowParallelLinear with ReplicatedLinear for the classification head. This is the correct approach because the classification logic is executed only on a single rank, and using a tensor-parallel layer like RowParallelLinear would lead to hangs or incorrect results due to its communication primitives. The use of ReplicatedLinear ensures the layer is treated as a standard, non-distributed module, which aligns with the single-rank execution context. The change is sound and effectively resolves the bug.

@noooop
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noooop commented Aug 28, 2025

Please set the threshold back to default

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>
@mergify mergify bot added the qwen Related to Qwen models label Aug 28, 2025
@DarkLight1337 DarkLight1337 enabled auto-merge (squash) August 28, 2025 15:28
@DarkLight1337 DarkLight1337 added the ready ONLY add when PR is ready to merge/full CI is needed label Aug 28, 2025
@DarkLight1337 DarkLight1337 merged commit 98ac0cb into vllm-project:main Aug 29, 2025
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@HelloZhang525
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Purpose

cc @HelloZhang525, can you check if this PR can solve the accuracy issue at TP=4? I only have 2 T4 GPU to investigate this.

Test Plan

Test Result

Essential Elements of an Effective PR Description Checklist

Problem solved! Big thanks!

@Isotr0py Isotr0py deleted the cls-score branch August 30, 2025 12:01
eicherseiji pushed a commit to eicherseiji/vllm that referenced this pull request Sep 9, 2025
FeiDaLI pushed a commit to FeiDaLI/vllm that referenced this pull request Sep 25, 2025
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qwen Related to Qwen models ready ONLY add when PR is ready to merge/full CI is needed

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[Bug]: Qwen3-Reranker + TP, with a significant loss in accuracy.

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