[Paper-Oral 8] LoftQ: LoRA-Fine-Tuning-Aware Quantization for Large Language Models

Quantization is an indispensable technique for serving Large Language Models(LLMs) and has recently found its way into LoRA fine-tuning (Dettmers et al.,2023). In this work we focus on the scenario where quantization and LoRA fine-tuning are applied together on a pre-trained model. In such cases it is commonto observe a consistent gap in the performance on downstream tasks between fullfine-tuning and quantization plus LoRA fine-tuning approach. In response, wepropose LoftQ (LoRA-Fine-Tuning-aware Quantization), a novel quantizationframework that simultaneously quantizes an LLM and finds a proper low-rankinitialization for LoRA fine-tuning. Such an initialization alleviates the discrep-ancy between the quantized and full-precision model and significantly improvesthe generalization in downstream tasks. We evaluate our method on natural lan-guage understanding, question answering, summarization, and natural languagegeneration tasks. Experiments show that our method is highly effective and out-performs existing quantization methods, especially in the challenging 2-bit and2/4-bit mixed precision regimes. We will release our code.