提出新方法提升多模态模型在剪枝后的全局视觉理解能力
Don't Just Chase "Highlighted Tokens" in MLLMs: Revisiting Visual Holistic Context Retention
- 从整体视觉上下文出发,动态分配剪枝预算以保留全局信息
- 在剪掉88.9%视觉标记时仍保持95.8%原始性能
- 适用于各类多模态模型,尤其适合高比例剪枝场景
尽管多模态大语言模型具备强大能力,但其依赖海量视觉标记导致显著计算开销。近期研究尝试通过标记剪枝缓解该问题,通常基于文本-视觉交叉注意力或[CLS]注意力评估并丢弃冗余标记。本文指出此类注意力优先剪枝方法存在关键缺陷:倾向于保留语义相似的标记,导致高剪枝率下性能严重下降。为此,我们提出HoloV——一种简单高效、即插即用的视觉标记剪枝框架。与以往注意力优先策略不同,HoloV从整体视觉上下文角度重新思考标记保留机制,通过自适应地在不同空间区域间分配剪枝预算,确保保留的标记捕捉全局视觉信息而非孤立显著特征。该策略有效避免表征坍塌,在激进剪枝下仍能维持任务相关性。实验表明,相比当前最优方法,HoloV在多种任务、模型架构和剪枝比例下均表现更优。例如,配备HoloV的LLaVA1.5在剪除88.9%视觉标记后仍保持95.8%原始性能,实现更优的效率-精度权衡。
原文摘要 · Abstract (English)
Despite their powerful capabilities, Multimodal Large Language Models (MLLMs) suffer from considerable computational overhead due to their reliance on massive visual tokens. Recent studies have explored token pruning to alleviate this problem, which typically uses text-vision cross-attention or [\texttt{CLS}] attention to assess and discard redundant visual tokens. In this work, we identify a critical limitation of such attention-first pruning approaches, i.e., they tend to preserve semantically similar tokens, resulting in pronounced performance drops under high pruning ratios. To this end, we propose {HoloV}, a simple yet effective, plug-and-play visual token pruning framework for efficient inference. Distinct from previous attention-first schemes, HoloV rethinks token retention from a holistic perspective. By adaptively distributing the pruning budget across different spatial crops, HoloV ensures that the retained tokens capture the global visual context rather than isolated salient features. This strategy minimizes representational collapse and maintains task-relevant information even under aggressive pruning. Experimental results demonstrate that our HoloV achieves superior performance across various tasks, MLLM architectures, and pruning ratios compared to SOTA methods. For instance, LLaVA1.5 equipped with HoloV preserves 95.8\% of the original performance after pruning 88.9\% of visual tokens, achieving superior efficiency-accuracy trade-offs.
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