One Rate Is Not Enough: Adaptive Anisotropic Learning Rates for LoRA Fine-Tuning

Huiyi Wang, Daijiao Liu, Lina Yao, Dong Gong


Abstract
Low-rank adaptation (LoRA) has become the standard for parameter-efficient fine-tuning of large language models. Most LoRA variants follow a uniform-LR convention, applying a single global learning rate across every rank-one component of every adapter. We show that this convention overlooks substantial within-module heterogeneity, where the rank-one components of a LoRA adapter update at highly uneven rates and low-velocity modules converge to concentrated singular spectra that underutilize the nominal rank budget. To address this, we propose an adaptive anisotropic learning-rate model that assigns each rank-one component its own effective learning rate, computed online from training-time signals and mean-normalized per module to preserve the global LR budget. AnLR-LoRA instantiates this model with two signals available during AdamW optimization, namely function-space velocity and Adam SNR, as a lightweight scheme with no extra trainable parameters. Across commonsense reasoning, natural language generation and visual instruction-tuning benchmarks, AnLR-LoRA consistently improves over LoRA while encouraging broader use of rank capacity, with gains that remain robust across a wide range of global learning rates and transfer cleanly to other LoRA variants.
Anthology ID:
2026.findings-emnlp.2469
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
53130–53149
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2469/
DOI:
Bibkey:
Cite (ACL):
Huiyi Wang, Daijiao Liu, Lina Yao, and Dong Gong. 2026. One Rate Is Not Enough: Adaptive Anisotropic Learning Rates for LoRA Fine-Tuning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 53130–53149, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
One Rate Is Not Enough: Adaptive Anisotropic Learning Rates for LoRA Fine-Tuning (Wang et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2469.pdf