基于LoRA的持续学习中任务驱动的子空间分解用于知识共享与隔离
Task-Driven Subspace Decomposition for Knowledge Sharing and Isolation in LoRA-based Continual Learning
AI总结:
提出LoDA方法,通过任务驱动分解构建通用和任务特定LoRA子空间,结合梯度对齐优化和闭式重校准,实现知识共享与隔离,提升持续学习性能。
摘要:
持续学习要求模型在不遗忘旧知识的情况下顺序适应新任务。最近,低秩适应(LoRA)作为一种代表性的参数高效微调方法,在持续学习中受到越来越多的关注。几种基于LoRA的持续学习方法通过分离更新空间来减少任务间的干扰,通常从过去任务的估计零空间中构建新空间。然而,它们(i)忽略了任务共享方向,抑制了知识迁移;(ii)未能捕获真正有效的任务特定方向,因为旧任务的这些“零基”在相关任务下对新任务几乎保持不活跃。为了解决这个问题,我们从投影能量的角度研究LoRA的学习能力,并提出了低秩分解与适应(LoDA)。它通过解决两个基于能量的目标,执行任务驱动分解以构建通用和真正的任务特定LoRA子空间,解耦知识共享和隔离的方向。LoDA固定两个子空间上的LoRA下投影,并通过梯度对齐优化方法学习鲁棒的上投影。在每个任务之后,在将LoRA更新集成到主干之前,LoDA为通用更新推导出一个闭式重校准,沿着这个任务共享方向近似特征级联合最优。实验表明,LoDA优于现有的持续学习方法。我们的代码可在https://github.com/HHHLF/LoDA_ICML2026获取。
英文摘要:
Continual Learning (CL) requires models to sequentially adapt to new tasks without forgetting old knowledge. Recently, Low-Rank Adaptation (LoRA), a representative Parameter-Efficient Fine-Tuning (PEFT) method, has gained increasing attention in CL. Several LoRA-based CL methods reduce interference across tasks by separating their update spaces, typically building the new space from the estimated null space of past tasks. However, they (i) overlook task-shared directions, which suppresses knowledge transfer, and (ii) fail to capture truly effective task-specific directions since these ``null bases" of old tasks can remain nearly inactive for new task under correlated tasks. To address this, we study LoRA learning capability from a projection energy perspective, and propose Low-rank Decomposition and Adaptation (LoDA). It performs a task-driven decomposition to build general and truly task-specific LoRA subspaces by solving two energy-based objectives, decoupling directions for knowledge sharing and isolation. LoDA fixes LoRA down-projections on two subspaces and learns robust up-projections via a Gradient-Aligned Optimization (GAO) approach. After each task, before integrating the LoRA updates into the backbone, LoDA derives a closed-form recalibration for the general update, approximating a feature-level joint optimum along this task-shared direction. Experiments indicate that LoDA outperforms existing CL methods. Our code is available at https://github.com/HHHLF/LoDA_ICML2026.
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