arXiv:2603.05204cs.LGcs.AI2026-03被引 1

提出Stable-LoRA,解决低秩微调的特征学习不稳定问题。

Stable-LoRA: Stabilizing Feature Learning of Low-Rank Adaptation

  • 通过动态收缩A矩阵提升LoRA训练稳定性。
  • 在多个模型和任务上均优于现有基线,性能显著提升。
  • 无需额外内存,计算开销极小,适合实际部署。

低秩适配(LoRA)是一种广泛使用的高效微调大语言模型的方法,其权重更新形式为 $W=W_0+sBA$,其中 $W_0$ 为冻结原始权重,$s$ 为缩放因子,$A$、$B$ 为可训练的低秩矩阵。尽管LoRA在实践中表现稳健,但其理论基础仍不充分,尤其在特征学习稳定性方面。本文首次证明,在合适超参数与初始化条件下,LoRA理论上可实现并维持稳定的特征学习(即自稳定)。然而,我们发现 $A$ 的非零初始化会破坏自稳定性,导致性能下降。为此,提出Stable-LoRA,一种基于权重收缩的优化策略,通过在训练初期逐步缩小 $A$ 来增强稳定性。该方法在理论和实验上均验证了其有效性,能消除特征学习不稳定性,同时保留非零初始化的优势。实验表明,Stable-LoRA在多种模型和任务中持续优于其他基线,无额外内存开销,仅带来可忽略的计算成本。代码已开源。

原文摘要 · Abstract (English)

Low-Rank Adaptation (LoRA) is a widely adopted parameter-efficient method for fine-tuning Large Langauge Models. It updates the weight matrix as $W=W_0+sBA$, where $W_0$ is the original frozen weight, $s$ is a scaling factor and $A$,$B$ are trainable low-rank matrices. Despite its robust empirical effectiveness, the theoretical foundations of LoRA remain insufficiently understood, particularly with respect to feature learning stability. In this paper, we first establish that, LoRA can, in principle, naturally achieve and sustain stable feature learning (i.e., be self-stabilized) under appropriate hyper-parameters and initializations of $A$ and $B$. However, we also uncover a fundamental limitation that the necessary non-zero initialization of $A$ compromises self-stability, leading to suboptimal performances. To address this challenge, we propose Stable-LoRA, a weight-shrinkage optimization strategy that dynamically enhances stability of LoRA feature learning. By progressively shrinking $A$ during the earliest training steps, Stable-LoRA is both theoretically and empirically validated to effectively eliminate instability of LoRA feature learning while preserving the benefits of the non-zero start. Experiments show that Stable-LoRA consistently outperforms other baselines across diverse models and tasks, with no additional memory usage and only negligible computation overheads. The code is available at https://github.com/Yize-Wu/Stable-LoRA.

低秩微调模型稳定大模型微调

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