Paper Detail

Automatic Rank Allocation for Low-Rank Adaptation in Large Language Models via lp Regularization

Zebang Xie, Chuanyang Zheng, Yik-Chung Wu, Yihang Gao

arxiv Score 6.2

Published 2026-09-24 · First seen 2026-09-26

General AI

Abstract

Low-rank adaptation (LoRA) has become a popular parameter-efficient fine-tuning method for large language models. A key challenge in LoRA is how to determine the rank of each adaptation matrix, as rank directly controls its capacity and efficiency. Existing adaptive-rank methods typically allocate ranks according to manually designed importance scores, which are not directly derived from an optimization objective. In this work, we propose $\ell_p$-LoRA, a principled rank-allocation method based on $\ell_p$ regularization with $0<p<1$, which is a classical sparsity-inducing technique in signal processing and statistics. Specifically, we regularize the energy of each rank-one LoRA component, encouraging redundant components to vanish while preserving important ones. We derive the corresponding proximal subproblem and reduce the matrix optimization to a two-dimensional problem, leading to an implicit thresholding criterion for identifying redundant components. Experiments on natural language understanding and question-answering tasks demonstrate that the proposed method achieves competitive performance with existing LoRA baselines.

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BibTeX

@article{xie2026automatic,
  title = {Automatic Rank Allocation for Low-Rank Adaptation in Large Language Models via lp Regularization},
  author = {Zebang Xie and Chuanyang Zheng and Yik-Chung Wu and Yihang Gao},
  year = {2026},
  abstract = {Low-rank adaptation (LoRA) has become a popular parameter-efficient fine-tuning method for large language models. A key challenge in LoRA is how to determine the rank of each adaptation matrix, as rank directly controls its capacity and efficiency. Existing adaptive-rank methods typically allocate ranks according to manually designed importance scores, which are not directly derived from an optimization objective. In this work, we propose \$\textbackslash{}ell\_p\$-LoRA, a principled rank-allocation method based },
  url = {https://arxiv.org/abs/2609.28998},
  keywords = {cs.LG},
  eprint = {2609.28998},
  archiveprefix = {arXiv},
}

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