通过可学习的层融合,动态重分配剪枝知识,提升大模型压缩效率。
From Pruning to Grafting: Dynamic Knowledge Redistribution via Learnable Layer Fusion
- 用动态评估指标与可学习低秩融合,实现剪枝后知识迁移。
- 25%稀疏度下性能超同类方法20%稀疏度,推理提速1.33倍。
- 适合追求高效部署的大模型应用,兼容量化等压缩技术。
结构化剪枝为生成式预训练大模型(GPT)的高效化提供了可行路径,但常因丢弃变换器块导致不可逆性能下降。本文提出FuseGPT,将结构化剪枝重构为迭代的知识嫁接过程。针对线性块合并无法捕捉非线性特征差异、块重要性在剪枝过程中动态变化的问题,FuseGPT采用双策略:首先提出宏影响(MI)指标,持续评估随网络拓扑演变的块冗余;其次引入可学习的低秩融合机制,通过轻量级局部蒸馏,自适应地将被剪枝块的知识嫁接到保留层上。在LLaMA、Mistral、Qwen和Phi系列模型上的实验表明,FuseGPT在压缩-精度帕累托前沿上达到新最优:25%稀疏度下,困惑度低于以往20%稀疏度方法,零样本推理能力提升最高4.5点,推理速度提升1.33倍,内存减少25%。此外,该方法与量化正交,结合4位GPTQ可实现52.1%总压缩率且质量损失极小。代码已开源:https://github.com/JarvisPei/FuseGPT。
原文摘要 · Abstract (English)
Structured pruning of Generative Pre-trained Transformers (GPTs) offers a promising path to efficiency but often suffers from irreversible performance degradation due to the discarding of transformer blocks. In this paper, we introduce FuseGPT, a compression paradigm that reframes structured pruning as iterative knowledge grafting rather than simple removal. Motivated by the observation that linear block merging fails to capture non-linear feature disparities and that block importance fluctuates dynamically during pruning, FuseGPT employs a dual-strategy pipeline. First, we propose Macro Influence (MI), a dynamic fusion-aware metric that continuously re-evaluates block redundancy as the network topology evolves. Second, instead of rigid parameter averaging, we introduce a learnable low-rank fusion mechanism that adaptively grafts the knowledge of pruned blocks onto surviving layers via lightweight local distillation. Extensive experiments on LLaMA, Mistral, Qwen, and Phi families demonstrate that FuseGPT establishes a new state-of-the-art on the compression-accuracy Pareto frontier: at 25\% sparsity, FuseGPT achieves lower perplexity than prior methods at 20\% sparsity, improves zero-shot reasoning by up to 4.5 points, and delivers 1.33$\times$ inference speedup with 25\% memory reduction. Furthermore, FuseGPT is orthogonal to quantization, achieving 52.1\% total compression with negligible quality loss when combined with 4-bit GPTQ. We make our code publicly available at https://github.com/JarvisPei/FuseGPT.
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