Delta-LoRA: Fine-Tuning High-Rank Parameters with the Delta of Low-Rank
  Matrices
Bojia Zi Xianbiao Qi Lingzhi Wang Jianan Wang Kam-Fai Wong Lei Zhang
In this paper, we present Delta-LoRA, which is a novel parameter-efficient
approach to fine-tune large language models (LLMs). In contrast to LoRA and
other low-rank adaptation methods such as AdaLoRA, Delta-LoRA not only updates
the low-rank matrices $\bA$ and $\bB$, but also propagate the learning to the
pre-trained weights $\bW$ via updates utilizing the delta of the product of two
low-rank matrices ($\bA^{(t+1)}\bB^{(t+1)} - \bA^{(t)}\bB^{(t)}$). Such a
strategy effectively addresses the limitation that the incremental update of
low-rank matrices is inadequate for learning representations capable for
downstream tasks. Moreover, as the update of $\bW$ does not need to compute the
gradients of $\bW$ and store their momentums, Delta-LoRA shares comparable
memory requirements and computational costs with LoRA. Extensive experiments
show that Delta-LoRA significantly outperforms existing low-rank adaptation
methods. We further support these results with comprehensive analyses that
underscore the effectiveness of Delta-LoRA.