针对视觉语言模型量化校准难题,提出细粒度分层校准新方法。
Rethinking Practical and Efficient Quantization Calibration for Vision-Language Models
- 按令牌重要性构建校准集,实现更精细的量化误差控制。
- 多GPU并行分层校准,降低对A100大内存依赖。
- 在2模型3尺度下均稳定提升性能,适合部署场景。
后训练量化(PTQ)是无需微调部署大语言模型的主要方法,其量化性能常受校准过程影响。然而,在视觉语言模型(VLMs)中,视觉与文本令牌在激活分布和对量化误差的敏感性上存在显著差异,给PTQ校准带来挑战。本文重新思考VLMs中PTQ校准应遵循的原则,提出令牌级重要性感知的分层量化框架(TLQ)。基于梯度信息设计令牌级重要性融合机制,构建令牌级校准集,实现更细粒度的校准策略。此外,TLQ引入多GPU、量化暴露的分层校准方案,使分层校准流程与真实量化推理路径一致,并将复杂校准任务分布至多张RTX3090 GPU,减少对A100大显存的依赖。TLQ在两个模型、三种模型规模及两种量化设置下均表现稳定,持续提升性能,验证了其强量化鲁棒性。代码将公开。
原文摘要 · Abstract (English)
Post-training quantization (PTQ) is a primary approach for deploying large language models without fine-tuning, and the quantized performance is often strongly affected by the calibration in PTQ. By contrast, in vision-language models (VLMs), substantial differences between visual and text tokens in their activation distributions and sensitivities to quantization error pose significant challenges for effective calibration during PTQ. In this work, we rethink what PTQ calibration should align with in VLMs and propose the Token-level Importance-aware Layer-wise Quantization framework (TLQ). Guided by gradient information, we design a token-level importance integration mechanism for quantization error, and use it to construct a token-level calibration set, enabling a more fine-grained calibration strategy. Furthermore, TLQ introduces a multi-GPU, quantization-exposed layer-wise calibration scheme. This scheme keeps the layer-wise calibration procedure consistent with the true quantized inference path and distributes the complex layer-wise calibration workload across multiple RTX3090 GPUs, thereby reducing reliance on the large memory of A100 GPUs. TLQ is evaluated across two models, three model scales, and two quantization settings, consistently achieving performance improvements across all settings, indicating its strong quantization stability. The code will be released publicly.
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