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arXiv 2605.09725cs.CV

基于N最佳教师轨迹选择的在线策略蒸馏

On-Policy Distillation with Best-of-N Teacher Rollout Selection

Johns Hopkins University(约翰霍普金斯大学);TikTok;University of California, San Diego(加州大学圣地亚哥分校);Fudan University(复旦大学)

Ke Zhang, Yunjie Tian, Dongdi Zhao, Yijiang Li, Yuanye Liu, Vishal M Patel, Di Fu

AI总结:

本文提出BRTS框架,通过选择更准确且与学生行为一致的教师轨迹提升在线策略蒸馏效果,在AIME和AMC基准测试中取得显著改进。

摘要:

在线策略蒸馏(OPD)通过自身采样的轨迹监督学生,已成为一种数据高效的后训练方法,用于提升推理能力并避免强化学习的奖励依赖和灾难性遗忘。然而,标准OPD通常在噪声学生生成上下文中计算教师监督,且通常依赖每个提示单一的随机教师轨迹。因此,监督信号可能具有高方差:采样的教师轨迹可能不正确、无信息或与学生当前推理行为不匹配。为了解决这一限制,我们提出BRTS,一种用于在线策略蒸馏的最佳-N轨迹选择框架。BRTS在标准学生-上下文OPD中增加一个教师-上下文监督分支,该分支由精心挑选的教师轨迹构建。与其从第一个采样的教师轨迹进行蒸馏,BRTS采样一个小的教师轨迹池,并使用简单的优先规则选择辅助轨迹:正确性优先,学生对齐其次。当多个正确的教师轨迹可用时,BRTS选择最与学生当前行为一致的轨迹;当无条件教师样本在更难的提示上失败时,它会调用真实条件恢复步骤以获得自然推导。所选轨迹随后用于在OPD循环中提供可靠的教师-上下文监督,并辅以教师轨迹的辅助损失。在AIME 2024、AIME 2025和AMC 2023上的实验表明,BRTS在挑战性推理基准测试中优于标准OPD,最大的收益出现在更难的数据集上。我们的代码可在https://github.com/BWGZK-keke/BRTS上获得。

英文摘要:

On-policy distillation (OPD), which supervises a student on its own sampled trajectories, has emerged as a data-efficient post-training method for improving reasoning while avoiding the reward dependence of reinforcement learning and the catastrophic forgetting often observed in standard supervised fine-tuning. However, standard OPD typically computes teacher supervision under noisy student-generated contexts and often relies on a single stochastic teacher rollout per prompt. As a result, the supervision signal can be high-variance: the sampled teacher trajectory can be incorrect, uninformative, or poorly matched to the student's current reasoning behavior. To address this limitation, we propose BRTS, a Best-of-N Rollout Teacher Selection framework for on-policy distillation. BRTS augments standard student-context OPD with a teacher-context supervision branch constructed from the curated teacher trajectory. Rather than distilling from the first sampled teacher rollout, BRTS samples a small pool of teacher trajectories and selects the auxiliary trajectory using a simple priority rule: correctness first, student alignment second. When multiple correct teacher trajectories are available, BRTS chooses the one most aligned with the student's current behavior; when unconditioned teacher samples fail on harder prompts, it invokes a ground-truth-conditioned recovery step to elicit a natural derivation. The selected trajectory is then used to provide reliable teacher-context supervision inside the OPD loop, augmented with an auxiliary loss on the teacher trajectory. Experiments on AIME 2024, AIME 2025, and AMC 2023 show that BRTS improves over standard OPD on challenging reasoning benchmarks, with the largest gains on harder datasets. Our code is available at https://github.com/BWGZK-keke/BRTS.

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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