提出新方法提升强化学习中自蒸馏的稳定性与效果
SR-OPSD: Self-Referenced On-Policy Self-Distillation

- 用变分方法定义自蒸馏目标为教师与参考策略的几何插值
- 通过Rényi散度调节投影方式,避免优化发散或分布过窄
- 在科学推理、数学解题等任务上表现优于现有方法
在策略自蒸馏(OPSD)中,反馈被转化为对策略生成轨迹的密集标记级监督,弥补稀疏奖励的不足。然而,传统方法中自教师策略是带梯度截断或指数移动平均的副本,并依赖额外上下文信息,导致其与学生策略及上下文分布共同演化。直接匹配这种动态目标可能引发优化不稳或分布过度集中。为此,本文提出自参考式在线策略自蒸馏(SR-OPSD)。在固定学生生成的上下文下,通过变分表征将有效蒸馏目标识别为自教师策略与参考策略之间的几何插值。同时,采用Rényi散度族推广投影几何结构,实现目标位置与投影方式的解耦:插值系数决定目标位置,Rényi阶数控制投影敏感度和密度比响应。在多个大语言模型上,覆盖科学评估、数学推理和代码生成任务的大量实验表明,SR-OPSD在各类设置下均达到或超越当前最优性能。
原文摘要 · Abstract (English)
On-policy self-distillation (OPSD) converts feedback into dense token-level supervision on trajectories generated by the policy to be optimized, providing a useful complement to reinforcement learning with sparse outcome rewards. However, the self-teacher policy used in OPSD is typically a stop-gradient or exponential-moving-average copy of the policy conditioned on additional context information, and thus co-evolves with both the student policy and its on-policy context distribution. Directly matching such a moving target with a fixed projection objective can lead to unstable optimization or excessive distributional concentration. This nature of OPSD motivates the proposed \emph{Self-Referenced On-Policy Self-Distillation (SR-OPSD)}. At fixed student-generated contexts, a token-level variational characterization identifies the effective distillation target as a geometric interpolation between the self-teacher policy and a reference policy. Meanwhile, we use the Rényi divergence family to generalize the projection geometry. This formulation separates \emph{where} the adaptive target is placed from \emph{how} the student is projected toward it: the interpolation coefficient controls underlying target, while the Rényi order controls the projection geometry and its sensitivity to token-level density ratios. Extensive experiments across scientific evaluation, mathematical reasoning, and coding generation tasks with multiple large language models show that SR-OPSD achieves the state-of-the-art or competitive performance across various settings.
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