One Initialization to Rule them All: Fine-tuning via Explained Variance
  Adaptation
Authors: name: Fabian Paischer; name: Lukas Hauzenberger; name: Thomas Schmied; name: Benedikt Alkin; name: Marc Peter Deisenroth; name: Sepp Hochreiter
Published: 2024-10-09 17:59:06

Abstract: Foundation models (FMs) are pre-trained on large-scale datasets and then
fine-tuned on a downstream task for a specific application. The most successful
and most commonly used fine-tuning method is to update the pre-trained weights
via a low-rank adaptation (LoRA). LoRA introduces new weight matrices that are
usually initialized at random with a uniform rank distribution across model
weights. Recent works focus on weight-driven initialization or learning of
adaptive ranks during training. Both approaches have only been investigated in
isolation, resulting in slow convergence or a uniform rank distribution, in
turn leading to sub-optimal performance. We propose to enhance LoRA by
initializing the new weights in a data-driven manner by computing singular
value decomposition on minibatches of activation vectors. Then, we initialize
the LoRA matrices with the obtained right-singular vectors and re-distribute
ranks among all weight matrices to explain the maximal amount of variance and
continue the standard LoRA fine-tuning procedure. This results in our new
method Explained Variance Adaptation (EVA). We apply EVA to a variety of
fine-tuning tasks ranging from language generation and understanding to image
classification and reinforcement learning. EVA exhibits faster convergence than
competitors and attains the highest average score across a multitude of tasks
per domain.