QuZO: Quantized Zeroth-Order Fine-Tuning for Large Language Models

TL;DR

QuZO introduces a low-precision, zeroth-order fine-tuning framework for large language models that avoids error-prone backpropagation and achieves high accuracy with reduced memory usage.

Contribution

The paper proposes QuZO, a novel zeroth-order fine-tuning method for quantized LLMs that improves training stability and efficiency in low-precision settings.

Findings

Achieves comparable performance to first-order methods in FP8.

Outperforms in INT8 and INT4 training accuracy.

Reduces memory cost by 2.94 times in LLaMA2-7B fine-tuning.

Abstract

Language Models (LLMs) are often quantized to lower precision to reduce the memory cost and latency in inference. However, quantization often degrades model performance, thus fine-tuning is required for various down-stream tasks. Traditional fine-tuning methods such as stochastic gradient descent and Adam optimization require backpropagation, which are error-prone in the low-precision settings. To overcome these limitations, we propose the Quantized Zeroth-Order (QuZO) framework, specifically designed for fine-tuning LLMs through low-precision (e.g., 4- or 8-bit) forward passes. Our method can avoid the error-prone low-precision straight-through estimator, and utilizes optimized stochastic rounding to mitigate the increased bias. QuZO simplifies the training process, while achieving results comparable to first-order methods in ${\rm FP}8$ and superior accuracy in ${\rm INT}8$ and ${\rm INT}4$ training. Experiments demonstrate that low-bit training QuZO achieves performance comparable to MeZO optimization on GLUE, Multi-Choice, and Generation tasks, while reducing memory cost by $2.94 \times$ in LLaMA2-7B fine-tuning compared to quantized first-order methods.