Efficient Safety Alignment of Large Language Models via Preference Re-ranking and Representation-based Reward Modeling

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Hauptverfasser: Deng, Qiyuan, Bai, Xuefeng, Chen, Kehai, Wang, Yaowei, Nie, Liqiang, Zhang, Min
Format: Preprint
Veröffentlicht: 2025
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author Deng, Qiyuan
Bai, Xuefeng
Chen, Kehai
Wang, Yaowei
Nie, Liqiang
Zhang, Min
author_facet Deng, Qiyuan
Bai, Xuefeng
Chen, Kehai
Wang, Yaowei
Nie, Liqiang
Zhang, Min
contents Reinforcement Learning (RL) algorithms for safety alignment of Large Language Models (LLMs), such as Direct Preference Optimization (DPO), encounter the challenge of distribution shift. Current approaches typically address this issue through online sampling from the target policy, which requires significant computational resources. In this paper, we hypothesize that during off-policy training, while the ranking order of output generated by policy changes, their overall distribution remains relatively stable. This stability allows the conversion of the sampling process from the target policy into a computationally efficient re-ranking of preference data. Building on this hypothesis, we propose a new framework that leverages the model's intrinsic safety judgment capability to extract reward signals, which are then used to calculate label confidence for preference reordering. Extensive experiments and theoretical analysis demonstrate that the proposed method effectively addresses the distribution shift issue, remarkably enhancing the safety performance while avoiding about 300x computational overheads.
format Preprint
id arxiv_https___arxiv_org_abs_2503_10093
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Efficient Safety Alignment of Large Language Models via Preference Re-ranking and Representation-based Reward Modeling
Deng, Qiyuan
Bai, Xuefeng
Chen, Kehai
Wang, Yaowei
Nie, Liqiang
Zhang, Min
Computation and Language
Reinforcement Learning (RL) algorithms for safety alignment of Large Language Models (LLMs), such as Direct Preference Optimization (DPO), encounter the challenge of distribution shift. Current approaches typically address this issue through online sampling from the target policy, which requires significant computational resources. In this paper, we hypothesize that during off-policy training, while the ranking order of output generated by policy changes, their overall distribution remains relatively stable. This stability allows the conversion of the sampling process from the target policy into a computationally efficient re-ranking of preference data. Building on this hypothesis, we propose a new framework that leverages the model's intrinsic safety judgment capability to extract reward signals, which are then used to calculate label confidence for preference reordering. Extensive experiments and theoretical analysis demonstrate that the proposed method effectively addresses the distribution shift issue, remarkably enhancing the safety performance while avoiding about 300x computational overheads.
title Efficient Safety Alignment of Large Language Models via Preference Re-ranking and Representation-based Reward Modeling
topic Computation and Language
url https://arxiv.org/abs/2503.10093