根据输入复杂度动态调整视觉令牌剪枝,提升大模型推理效率。
AutoPrune: Each Complexity Deserves a Pruning Policy
- 基于视觉与文本令牌互信息生成自适应剪枝策略
- 剪掉89%视觉令牌,降低76.8%计算量,保留96.7%准确率
- 无需训练、即插即用,适合不同任务和输入复杂度
大型视觉语言模型中存在显著的视觉令牌冗余,剪枝可有效降低其计算开销。现有方法通常采用启发式分层剪枝策略,虽各解码层剪枝数量不同,但整体剪枝方案固定,对所有输入样本和任务统一应用,无法与模型整体推理轨迹对齐。认知科学表明,人类视觉处理先广域探索积累证据,后聚焦目标。我们实验发现模型亦呈现类似模式。这说明固定剪枝方案或启发式分层策略难以适配不同输入的多样性复杂度。为此,我们提出无需训练、即插即用的复杂度自适应剪枝(AutoPrune)框架,根据输入复杂度动态定制剪枝策略。具体而言,AutoPrune量化视觉与文本令牌间的互信息,并将其投影至预算受限的逻辑保留曲线。每条逻辑曲线由其独特形状表征特定任务复杂度,可保证满足预设计算约束。我们在标准视觉语言任务及自动驾驶多模态动作模型上评估了AutoPrune。以LLaVA-1.5-7B为例,该方法剪除89%视觉令牌,推理浮点运算减少76.8%,平均准确率保持在96.7%,较近期工作PDrop提升9.1%,验证了有效性。代码已开源:https://github.com/AutoLab-SAI-SJTU/AutoPrune。
原文摘要 · Abstract (English)
The established redundancy in visual tokens within large vision-language models allows pruning to effectively reduce their substantial computational demands. Previous methods typically employ heuristic layer-specific pruning strategies where, although the number of tokens removed may differ across decoder layers, the overall pruning schedule is fixed and applied uniformly to all input samples and tasks, failing to align token elimination with the model's holistic reasoning trajectory. Cognitive science indicates that human visual processing often begins with broad exploration to accumulate evidence before narrowing focus as the target becomes distinct. Our experiments reveal an analogous pattern in these models. This observation suggests that neither a fixed pruning schedule nor a heuristic layer-wise strategy can optimally accommodate the diverse complexities inherent in different inputs. To overcome this limitation, we introduce Complexity-Adaptive Pruning (AutoPrune), a training-free, plug-and-play framework that tailors pruning policies to varying sample and task complexities. Specifically, AutoPrune quantifies the mutual information between visual and textual tokens, then projects this signal to a budget-constrained logistic retention curve. Each such logistic curve, defined by its unique shape, corresponds to the specific complexity of different tasks and can guarantee adherence to predefined computational constraints. We evaluate AutoPrune on standard vision-language tasks and on Vision-Language-Action models for autonomous driving. Notably, when applied to LLaVA-1.5-7B, our method prunes 89% of visual tokens and reduces inference FLOPs by 76.8% while retaining 96.7% of the original accuracy averaged over all tasks. This corresponds to a 9.1% improvement over the recent work PDrop, demonstrating the effectiveness. Code is available at https://github.com/AutoLab-SAI-SJTU/AutoPrune.
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