用轻量新手替换冗余专家,实现MoE模型高效压缩
MoNE: Replacing Redundant Experts with Lightweight Novices for Structured Pruning of MoE
- 通过访问频率和输出方差判断专家冗余,用轻量新手替代
- 25%剪枝率下零样本平均准确率提升2.72,性能下降仅0.14
- 对架构/数据源/样本量变化均稳定,适合部署优化
混合专家(MoE)通过每输入词元仅激活部分专家实现大语言模型的高效扩展。然而,部署MoE模型需将所有专家保留在内存中,带来显著内存开销。结构化剪枝虽有望降低内存成本,但现有方法在模型架构、校准数据源和校准样本量三个维度上常出现性能不佳与不稳定退化。本文提出混合新手与专家(MoNE)的新剪枝方法,通过评估专家的访问频率和输出方差,将低频使用且输出稳定的冗余专家替换为轻量级新手——其原输出的无偏估计,从而最小化性能损失。大量实验表明,MoNE在三个维度上均显著优于基线方法,性能衰减极小。尤其在25%剪枝率下,九项下游任务的平均零样本准确率最高提升2.72,对Qwen2-57B-A14B仅造成0.14的性能下降。
原文摘要 · Abstract (English)
Mixture-of-Experts (MoE) enables efficient scaling of large language models by activating only a subset of experts per input token. However, deploying MoE-based models incurs significant memory overhead due to the need to retain all experts in memory. While structured pruning is promising to reduce memory costs, existing methods often show suboptimal performance and unstable degradation in three dimensions: model architectures, calibration data sources, and calibration sample sizes. This paper proposes Mixture-of-Novices-and-Experts (MoNE), a novel expert pruning method that replaces redundant experts with lightweight novices to achieve effective and robust model compression. MoNE evaluates expert redundancy based on two metrics: access frequency and output variance. Experts exhibiting low usage and stable outputs are pruned and replaced with lightweight novices-unbiased estimations of their original outputs-minimizing performance degradation. Extensive experiments demonstrate that MoNE consistently outperforms baseline methods with minimal accuracy degradation across the three dimensions, confirming its effectiveness and robustness. Notably, it outperforms baselines by up to 2.72 for the average zero shot accuracy across nine downstream tasks under 25% pruning ratio, with only 0.14 performance drop for Qwen2-57B-A14B. The code is available at https://github.com/zxgx/mode-pd.
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