[AMD] fix: ensure scheme attribute exists before type checking in MoriEPMoE

[Duyi-Wang]

Motivation

As modified in #18252, the scheme is now used to check whether is mxfp4 instead of quant_method. However, scheme is not initialized in the FP8 case, which results in the error: AttributeError: 'MoriEPMoE' object has no attribute 'scheme'.

Modifications

Accuracy Tests

Benchmarking and Profiling

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[gemini-code-assist]

Summary of Changes

Hello @Duyi-Wang, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the stability of the MoriEPMoE layer by preventing a runtime error that could arise from accessing an uninitialized attribute. It introduces a safeguard to ensure that the scheme attribute exists before performing type-based checks, which is crucial for scenarios involving different quantization methods like FP8 where this attribute might not be set.

Highlights

• Bug Fix: Resolved an AttributeError in the MoriEPMoE class that occurred when the scheme attribute was accessed without being initialized, specifically in FP8 quantization cases.
• Robustness Improvement: Added a check using hasattr(self, "scheme") before attempting to type-check the self.scheme attribute, ensuring the code safely handles cases where scheme might not be present.

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Changelog

• python/sglang/srt/layers/moe/ep_moe/layer.py
  • Modified the is_quark_w4a4 check to first verify the existence of the scheme attribute using hasattr before checking its type.

Activity

• The pull request was opened by Duyi-Wang to address an AttributeError related to the scheme attribute in MoriEPMoE.

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[gemini-code-assist]

Code Review

This pull request correctly fixes a potential AttributeError in MoriEPMoE.forward by ensuring the scheme attribute exists before it's accessed for a type check. The change is simple, direct, and effectively resolves the issue described, which occurs when using FP8 quantization where scheme is not initialized. The fix is sound and improves the robustness of the code.