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arXiv 2603.08058cs.LG

在联邦学习中使用LoRA的稳定微调:通过缩放因子缓解客户端大小和秩的副作用

Stabilized Fine-Tuning with LoRA in Federated Learning: Mitigating the Side Effect of Client Size and Rank via the Scaling Factor

Beijing University of Posts and Telecommunications(北京邮电大学);Agency for Science, Technology and Research(科技研究局)

Jiayu Huang, Xiaohu Wu, Tiantian He, Qicheng Lao

AI总结:

本文提出SFed-LoRA,通过理论分析适配器秩与联邦聚合的相互作用,设计最优缩放因子以缓解高秩适配器在联邦学习中的梯度崩溃问题,提升稳定性和收敛速度。

摘要:

大型语言模型(LLMs)在自然语言处理中至关重要。全微调的不现实性促使了参数高效微调(PEFT)方法,如低秩适应(LoRA),优化低秩矩阵A和B。然而,在隐私约束要求联邦学习(FL)的分布式场景中,LoRA的整合往往不稳定。具体来说,我们发现聚合多个客户端的更新引入了随客户端数量增加而增加的统计方差,导致使用高秩适配器时出现梯度崩溃。现有的缩放因子候选者,如Rank-Stabilized LoRA所用的,忽略了聚合过程引起的相互作用。为弥合这一差距,本文引入了稳定联邦LoRA(SFed-LoRA),一个框架,该框架理论上表征了适配器秩与联邦聚合之间的相互作用。我们推导出一个最优缩放因子,旨在有效缓解在N个客户端中累积的聚合误差。通过纠正先前方法中固有的缩放不匹配,SFed-LoRA在不改变原始模型架构或增加推断延迟的情况下恢复了高秩适应的有效性。在多样化的任务、模型架构和异质数据分布中进行了广泛的实验以验证我们的结果。我们证明,SFed-LoRA防止了高秩崩溃,并在高秩适应的最先进基线中实现了显著改进的稳定性和更快的收敛速度。

英文摘要:

Large Language Models (LLMs) are pivotal in natural language processing. The impracticality of full fine-tuning has prompted Parameter-Efficient Fine-Tuning (PEFT) methods like Low-Rank Adaptation (LoRA), optimizing low-rank matrices A and B. In distributed scenarios where privacy constraints necessitate Federated Learning (FL), however, the integration of LoRA is often unstable. Specifically, we identify that aggregating updates from multiple clients introduces statistical variance that scales with the client count, causing gradient collapse when using high-rank adapters. Existing scaling factor candidates, such as the one used by Rank-Stabilized LoRA, ignore the interaction caused by the aggregation process. To bridge this gap, this paper introduces Stabilized Federated LoRA (SFed-LoRA), a framework that theoretically characterizes the interaction between adapter rank and federated aggregation. We derive an optimal scaling factor designed to effectively mitigate the aggregation error accumulating across N clients. By correcting the scaling mismatch inherent in previous approaches, SFed-LoRA restores the efficacy of high-rank adaptation without altering the original model architecture or increasing inference latency. Extensive experiments in diverse tasks, model architectures, and heterogeneous data distributions are conducted to validate our results. We demonstrate that SFed-LoRA prevents high-rank collapse, and achieves significantly improved stability and faster convergence compared with state-of-the-art baselines for high-rank adaptation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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