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arXiv 2410.20187cs.LGcs.AIstat.ML
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不确定性惩罚的直接偏好优化

Uncertainty-Penalized Direct Preference Optimization

ETH Zurich(苏黎世联邦理工学院);ETH AI Center(ETH人工智能中心);Max Planck Institute for Intelligent Systems(马克斯·普朗克智能系统研究所)

Sam Houliston, Alizée Pace, Alexander Immer, Gunnar Rätsch

AI总结:

针对 DPO 中模糊或错标偏好对导致的奖励过度优化问题,本文引入受离线强化学习启发的不确定性惩罚,减弱高不确定样本梯度,并在 GPT2 Medium 与 Anthropic-HH 上验证其优于原始 DPO。

摘要:

使大型语言模型(LLM)在内容、风格和呈现方式上与人类偏好对齐具有挑战性,部分原因在于偏好多种多样、依赖上下文,有时还具有内在的模糊性。尽管基于人类反馈的强化学习(RLHF)和直接偏好优化(DPO)已经取得成功,但它们容易出现代理奖励过度优化的问题。对 DPO 损失的分析表明,迫切需要对标记错误或模糊的偏好对进行正则化,以避免奖励作弊。在本工作中,我们受离线强化学习启发,通过引入偏好不确定性惩罚方案,为 DPO 开发了一个悲观框架。该惩罚作为对损失的修正,会减弱不确定样本的损失梯度。我们使用 GPT2 Medium 在 Anthropic-HH 数据集上评估这些方法,并利用模型集成获得不确定性估计;结果表明,与原始 DPO 相比,其总体性能有所提升,并且在来自高不确定性的所选/所拒响应的提示上产生了更好的补全。

英文摘要:

Aligning Large Language Models (LLMs) to human preferences in content, style, and presentation is challenging, in part because preferences are varied, context-dependent, and sometimes inherently ambiguous. While successful, Reinforcement Learning from Human Feedback (RLHF) and Direct Preference Optimization (DPO) are prone to the issue of proxy reward overoptimization. Analysis of the DPO loss reveals a critical need for regularization for mislabeled or ambiguous preference pairs to avoid reward hacking. In this work, we develop a pessimistic framework for DPO by introducing preference uncertainty penalization schemes, inspired by offline reinforcement learning. The penalization serves as a correction to the loss which attenuates the loss gradient for uncertain samples. Evaluation of the methods is performed with GPT2 Medium on the Anthropic-HH dataset using a model ensemble to obtain uncertainty estimates, and shows improved overall performance compared to vanilla DPO, as well as better completions on prompts from high-uncertainty chosen/rejected responses.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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