arXiv Machine Learning

$D^2$-OPD: Separating Direction and Distance in Extrapolative On-Policy Distillation

$D^2$-OPD is a new on‑policy distillation method that separates the direction and distance of extrapolation when training a student model to match a teacher’s next‑token distributions. It introduces a per‑prefix hard KL constraint to bound the target’s distance from the teacher and an adaptive combination of the teacher’s post‑training shift with the initial student–teacher gap to set the extrapolation direction. Experiments on mathematical reasoning benchmarks show that $D^2$-OPD achieves the highest scores across three challenging settings, outperforming the strongest baseline by up to 9.45 points, with ablations confirming the value of each component.

arXiv Computation and Language
2d ago

Meet Students Where They Are: Student-Prefix Teacher Adaptation for On-Policy Distillation

The paper introduces Student‑Prefix Teacher Adaptation (SPTA), a method that trains a teacher model to better handle student‑generated prefixes before performing on‑policy distillation (OPD). By collecting prefixes of random lengths and using reinforcement learning with verifiable rewards (RLVR), the teacher learns to recover from student‑induced states rather than simply imitate the student’s reasoning. Experiments on mathematical reasoning benchmarks show that SPTA improves student performance compared to standard OPD and OPD with task‑level RLVR‑adapted teachers.

By Xue Zhang, Songming Zhang, Yunlong Liang, Fandong Meng, Yufeng Chen, Jinan Xu
arXiv AI
Oct 7

E$^2$-OPSD: Taming Entropy Overshoot in On-Policy Self-Distillation

E$^2$-OPSD tackles a failure mode in on‑policy self‑distillation where the student’s token entropy surpasses the teacher’s, a problem called entropy overshoot. The method replaces the teacher’s answer with a retrieved solved neighboring problem to provide transferable reasoning guidance and uses the student‑teacher entropy gap to adjust token corrections. These changes improve math reasoning scores by up to 4.3 points in mean@16 and yield out‑of‑domain gains of up to 4.9 points in mean@16 and 5.5 points in pass@8, all without extra forward passes or networks.

By Yifei Liu, Minghao Fang, Xinyu Gu, Chengkai Yao, Mengdi Liu, Tengfei Ma, Jiangbin Zheng, Chang Yu, Zhangyang Gao
arXiv Machine Learning
Oct 16

Waypoint-OPD: Transferring RL-Induced Policy Shifts via Gated On-Policy Distillation

Waypoint-OPD is a new on-policy distillation method that leverages an intermediate teacher checkpoint to compare early and late policy shifts in reinforcement learning. By gating the endpoint shift based on the directional agreement between these early and late shifts, the method suppresses conflicting updates and requires only one additional frozen-teacher scoring pass. Experiments with Qwen3-4B teachers and larger Qwen3 student models in mathematical and code reasoning tasks show that Waypoint-OPD consistently outperforms endpoint-only transfer across all six domain–student settings.

By Bingxi Hou, Guochao Jiang, Guofeng Quan, Weiqing Li, Wenfeng Feng, Guohua Liu, Yuewei Zhang
arXiv AI
Oct 28

Proposing Better Rollouts for On-Policy Distillation

The paper proposes Mixture Proposal On-Policy Distillation (MPOPD) to address a mismatch issue in on‑policy distillation (OPD) where the rollout policy is fixed to the current student. By treating the rollout policy as an optimization target, MPOPD derives a geometric mixture of student and teacher policies and introduces a proposal policy for efficient rollout generation. Experiments on 16 reasoning benchmarks show consistent gains over OPD, notably a 6.91% accuracy improvement on math reasoning with Qwen3-4B-Base and a 41% reduction in generation length.

By Sirui Chen, Yunzhe Qi, Haobo Xu, Jiaru Zou, Mengting Ai, Zihao Li, Jingrui He
arXiv AI
Oct 1

On the Off-Policy Teacher in On-Policy Distillation

The paper introduces SCOUT, a co‑training framework that adapts an off‑policy teacher to better continue from student‑generated prefixes in on‑policy distillation (OPD). By periodically optimizing the teacher’s conditional continuation ability using reinforcement learning with verifiable rewards, SCOUT improves the teacher’s performance on student prefixes. Experiments across various teacher‑student setups, model scales, and reasoning domains show that SCOUT consistently enhances the effectiveness of OPD.

By Langlin Huang, Hao Liu, Mononito Goswami, Xinyu Li, Prithwith Jana, Nikos Kanakaris, Patrick Bl\"obaum, Purak Jain