How Much Rank Does LoRA Need? Rank-Error Bounds for Transformer Attention

Choosing the rank of a low-rank adaptation (LoRA) update is usually an empirical task.

Choosing the rank of a low-rank adaptation (LoRA) update is usually an empirical task. In this paper, we provide a task-dependent theory of the approximation error achievable at each LoRA rank for Transformer attention. We fix a pretrained attention head, a target attention…