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[Bugfix] QAC with basic pipeline#2462

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kylesayrs wants to merge 1 commit intomainfrom
kylesayrs/basic-gptq
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[Bugfix] QAC with basic pipeline#2462
kylesayrs wants to merge 1 commit intomainfrom
kylesayrs/basic-gptq

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@kylesayrs
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Purpose

  • Support modifiers which disable quantization-aware-calibration like GPTQ in the basic pipeline

Changes

  • Disable QAC in the basic pipeline for DISABLE_QAC_MODIFIERS

Signed-off-by: Kyle Sayers <kylesayrs@a100-02.nemg-001.lab.rdu2.dc.redhat.com>
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👋 Hi! Thank you for contributing to llm-compressor. Please add the ready label when the PR is ready for review.

Note: This is required to complete the testing suite, please only add the label once the PR is code complete and local testing has been performed.

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Summary of Changes

Hello, 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 addresses a bug by enhancing the basic pipeline to support modifiers that necessitate the disabling of Quantization-Aware Calibration (QAC). The changes ensure that the calibration process correctly adapts to specific quantization techniques, such as GPTQ, by providing a mechanism to selectively bypass QAC when required, thereby improving the robustness and compatibility of the compression pipeline.

Highlights

  • Quantization-Aware Calibration (QAC) Control: Introduced functionality to conditionally disable Quantization-Aware Calibration (QAC) within the basic pipeline.
  • Modifier Compatibility: Implemented a mechanism to detect specific modifiers (e.g., GPTQ) that require QAC to be disabled, ensuring proper compatibility.
  • Dynamic Quantization Disablement: Added a conditional context manager to disable quantization during calibration if QAC is not desired or if a disabling modifier is present.

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Changelog
  • src/llmcompressor/pipelines/basic/pipeline.py
    • Imported DISABLE_QAC_MODIFIERS and DisableQuantization from llmcompressor.utils.helpers.
    • Added logic to check for modifiers that disable QAC and conditionally apply a DisableQuantization context during calibration.
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Code Review

This pull request aims to disable quantization-aware calibration (QAC) for certain modifiers like GPTQ in the basic pipeline. The implementation correctly identifies when to disable QAC based on the active modifiers. However, I found a critical issue where the code does not handle cases where dataset_args is None, which will lead to a crash. I've provided a suggestion to fix this.

with contextlib.ExitStack() as stack:
stack.enter_context(calibration_forward_context(model))
# Optionally disable quantization
if not dataset_args.quantization_aware_calibration or disable_qac:
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critical

The dataset_args object can be None, for example when the run_calibration helper function is used. In that case, accessing dataset_args.quantization_aware_calibration will raise an AttributeError.

You should handle the case where dataset_args is None. Based on the DatasetArguments definition, the default value for quantization_aware_calibration is True, which should be used when dataset_args is not provided.

Suggested change
if not dataset_args.quantization_aware_calibration or disable_qac:
if not (dataset_args.quantization_aware_calibration if dataset_args else True) or disable_qac:

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mergify bot commented Mar 10, 2026

The quality checks have failed. Please run make style and make quality under
the root directory to adddress the lint failures. You will need to install the
dev optional install to get the required linting packages:
https://github.com/vllm-project/llm-compressor/blob/main/CONTRIBUTING.md

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