LoRA-XS: Low-Rank Adaptation with Extremely Small Number of Parameters

원문 초록

The rapid expansion of large language models (LLMs) has underscored the need for parameter-efficient fine-tuning methods, with LoRA (Low-Rank Adaptation) emerging as a popular solution. Although LoRA reduces the number of trainable parameters, serving multiple (task or user-specific) LoRA modules on top of a base model still creates significant storage challenges. To address this, using theoretical derivation, we introduce LoRA-XS (Low-Rank Adaptation with eXtremely Small number of parameters), a novel low-rank adaptation method that considerably reduces the trainable parameters while showing superior or competitive performance. LoRA-XS achieves this by inserting a small, trainable r x r weight matrix between frozen low-rank matrices, which are constructed by Singular Value Decomposition (SVD) of the original weight matrix. This lightweight matrix enables fine-tuning with drastically reduced storage requirements, making it feasible to deploy millions of personalized models while minimizing memory overhead. For instance, LoRA-XS achieves a remarkable reduction of trainable parameters by over 100x in 7B models compared to LoRA. Our evaluations across various benchmarks (including GLUE, GSM8K, MATH, and eight commonsense reasoning datasets) demonstrate that LoRA-XS performs competitively or better than LoRA and other recent methods like VeRA while being significantly more parameter efficient. We also provide an extensive ablation study on the importance of singular vectors in transformer weights, shedding light on the underlying mechanisms driving LoRA-XS's enhanced efficiency. These findings suggest that LoRA-XS is not only a storage-efficient alternative, but also a powerful tool for scaling and personalizing LLMs at unprecedented scales.