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About this paper

Uijeong Jang, Jason D. Lee, Ernest K. Ryu

This work theoretically analyzes Low-Rank Adaptation (LoRA) within the Neural Tangent Kernel (NTK) regime, establishing that the optimization landscape of LoRA fine-tuning is free of spurious local minima under certain conditions and that the resulting solutions generalize well. It demonstrates that optimal weight updates in this regime are inherently low-rank and provides quantitative guarantees for trainability and generalization.

Key insights

  • Even full fine-tuning in the NTK regime yields low-rank optimal weight updates, specifically with rank $r$ such that $r(r+1)/2 \le KN$, where $K$ is output dimension and $N$ is data points.
  • For LoRA ranks $r$ satisfying $r(r+1)/2 > KN$, a slightly perturbed loss function has no spurious local minima, ensuring gradient-based optimizers converge to global optima.
  • LoRA solutions found under these conditions possess strong generalization guarantees, bounded by factors including the nuclear norm of the optimal solution and data size.

Summary by alphaXiv.

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