arXiv:2502.14272cs.CLcs.AI2025-02ACL被引 7

让小模型更懂人类细微偏好,效果超越大模型老师。

Capturing Nuanced Preferences: Preference-Aligned Distillation for Small Language Models

  • 用概率分布建模大模型的偏好差异,提供更精细监督信号。
  • 在多个基准上提升超20%,部分场景小模型反超大模型。
  • 适合追求高精度对齐的小模型应用,如智能客服、内容生成。

将小语言模型(SLMs)对齐人类价值观通常依赖从大语言模型(LLMs)中蒸馏偏好知识。现有方法通过比较成对响应来建模教师模型的偏好,忽略了响应间的差异程度,限制了学生模型捕捉多响应细微偏好的能力。本文提出偏好对齐蒸馏(PAD)框架,将教师偏好知识建模为所有潜在偏好的概率分布,从而提供更细致的监督信号。核心思路是:语言模型可作为奖励函数,反映其内在偏好。PAD包含三个步骤:(1) 采用高温采样生成多样化响应;(2) 计算师生模型的奖励以构建其内在偏好;(3) 训练学生模型的内在偏好分布以对齐教师。在四个主流对齐基准上的实验表明,PAD显著优于现有方法,在AlpacaEval 2和Arena-Hard上提升超过20%;在MT-Bench上,使用Gemma模型家族时,学生模型性能超越教师模型,验证了该方法的有效性。

原文摘要 · Abstract (English)

Aligning small language models (SLMs) with human values typically involves distilling preference knowledge from large language models (LLMs). However, existing distillation methods model preference knowledge in teacher LLMs by comparing pairwise responses, overlooking the extent of difference between responses. This limitation hinders student SLMs from capturing the nuanced preferences for multiple responses. In this paper, we propose a Preference-Aligned Distillation (PAD) framework, which models teacher's preference knowledge as a probability distribution over all potential preferences, thereby providing more nuanced supervisory signals. Our insight in developing PAD is rooted in the demonstration that language models can serve as reward functions, reflecting their intrinsic preferences. Based on this, PAD comprises three key steps: (1) sampling diverse responses using high-temperature; (2) computing rewards for both teacher and student to construct their intrinsic preference; and (3) training the student's intrinsic preference distribution to align with the teacher's. Experiments on four mainstream alignment benchmarks demonstrate that PAD consistently and significantly outperforms existing approaches, achieving over 20\% improvement on AlpacaEval 2 and Arena-Hard, indicating superior alignment with human preferences. Notably, on MT-Bench, using the \textsc{Gemma} model family, the student trained by PAD surpasses its teacher, further validating the effectiveness of our PAD.

小模型对齐偏好蒸馏大模型压缩人类对齐

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