arXiv Machine Learning

From What Is Used to What Is Missing: Rethinking Dynamic Rank in LoRA

arXiv Machine Learning
Sep 14

Rank-Efficient LoRA via Joint Tangent-Space Optimization under Isotropic Curvature

The paper introduces ISO-LoRA, an optimizer that improves rank utilization in Low‑Rank Adaptation (LoRA) by coupling factor updates through spectral descent on the induced tangent perturbation in weight space. Experiments on GPT‑2 adaptation show that standard optimizers like AdamW concentrate updates in a few singular directions, whereas ISO-LoRA distributes energy more evenly, leading to higher effective rank and better downstream performance across 0.1B‑7B models. The authors provide theoretical guarantees under a stylized spiked‑gradient model and demonstrate that ISO-LoRA consistently outperforms factor‑wise optimizers, especially at moderate‑to‑large LoRA ranks.

By Zihan Zhu, Zhehang Du, Xuyang Chen, Tim Tsz-Kit Lau, Jiayuan Wu, X. Y. Han, Qi Long, Weijie Su
arXiv Machine Learning
Sep 3

LoRA-TSD: Tangent-Space Spectral Descent for LoRA via Muon-Style Updates

LoRA-TSD introduces a new optimizer for low‑rank adaptation (LoRA) that treats each update as a tangent vector on the fixed‑rank matrix manifold and applies a Muon‑style spectral‑norm steepest‑descent step within that tangent space. The method avoids costly full‑matrix operations and offers a retraction that is up to 2.8× cheaper than previous manifold approaches. The authors prove that their surrogate recovers LoRA‑Pro, identify the Riemannian gradient as the natural stationarity measure, and provide the first global convergence guarantees for both LoRA‑Pro and LoRA‑TSD, achieving superior performance across multiple benchmarks with Llama and Qwen models.

By Dmitrii Andriianov, Andrey Veprikov, Aleksandr Beznosikov
Hugging Face Trending Papers
Sep 2

LoRA-TSD: Tangent-Space Spectral Descent for LoRA via Muon-Style Updates

Low-rank adaptation (LoRA) is the standard way to fine-tune large models, yet when its two factors are trained independently, the update ignores the geometry of the low-rank weight change it induces. We introduce LoRA-TSD, an optimizer that treats every LoRA step as a tangent vector of the fixed-rank matrix manifold and takes the spectral-norm steepest-descent step of Muon inside that tangent space, mapping the result back to the factors through a retraction native to the LoRA parametrization.

arXiv AI
Oct 28

LoRA on a Budget: Function-Aware Post-Hoc Compression for Adapter Fleets

The paper introduces Functional Rank Allocation (FRA), a method for post‑hoc compression of LoRA adapters that balances rank allocation across layers and adapters within a shared budget. FRA constructs functional rank‑distortion frontiers for each adapter, uses dynamic programming to search for low‑risk truncations, and then applies minimax allocation to optimize overall fleet performance. Experiments on 78 adapters from three public fleets show that FRA outperforms uniform spectral compression, especially in constrained‑budget scenarios.

By Shenghui Li, Thiemo voigt
arXiv AI
Jun 12

The Hidden Power of Scaling Factor in LoRA Optimization

arXiv:2606. 12883v1 Announce Type: new Abstract: In Low-Rank Adaptation (LoRA), the scaling factor $\alpha$ is often treated as a mere complement to the learning rate, yet its role in optimization remains poorly understood.

By Zicheng Zhang, Haoran Li, Jiaxing Wang, Guoqiang Gong, Anqi Li, Yudong Hu, Ting Xiong, Yurong Gao, Junxing Hu, Zhida Jiang, Yifeng Zhang, Pengzhang Liu, Qixia Jiang