Robust Preference Optimization via Dynamic Target Margins

TL;DR

This paper introduces $oldsymbol{ extgamma}$-PO, a dynamic margin preference optimization method that improves Large Language Model alignment by adaptively calibrating reward margins at the pair level, boosting performance with minimal efficiency loss.

Contribution

The paper proposes $oldsymbol{ extgamma}$-PO, a novel, plug-and-play dynamic margin calibration technique that enhances preference optimization for LLMs by effectively handling noisy data.

Findings

Achieves 4.4% average improvement on benchmarks

Sets new state-of-the-art performance for LLM alignment

Requires minimal code changes and maintains training efficiency

Abstract

The alignment of Large Language Models (LLMs) is crucial for ensuring their safety and reliability in practical applications. Direct Preference Optimization (DPO) has emerged as an efficient method that directly optimizes models using preference pairs, significantly reducing resource demands. However, the effectiveness of DPO heavily depends on the data quality, which is frequently compromised by noise. In this work, we propose $\gamma$-PO, a dynamic target margin preference optimization algorithm that adjust reward margins at the pairwise level. By introducing instance-specific margin calibration, $\gamma$-PO strategically prioritizes high-confidence pairs (those demonstrating higher reward margins) while suppressing potential noise from ambiguous pairs. Moreover, $\gamma$-PO is a plug-and-play method, compatible with variants of DPO that rely on reward margin between preference pairs. Across benchmarks such as AlpacaEval2 and Arena-Hard, $\gamma$-PO achieves an average 4.4\% improvement over other baselines, setting new benchmarks for state-of-the-art performance. Additionally, $\gamma$-PO requires minimal code changes and has a negligible impact on training efficiency, making it a robust solution for enhancing LLMs alignment. Our codes are available at \href{https://github.com/sunjie279/gammaPO}{https://github.com/sunjie279/gammaPO}.