arXiv AI By Jingyuan Huang, Zuming Huang, Yucheng Shi, Zhongzhi Li, Xiaoming Zhai, Wei Chu, Ninghao Liu

Train4Merge: RL or SFT---Which Yields Better Teachers for OPD-Based Model Merging?

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The study compares supervised fine‑tuning (SFT) and reinforcement learning (RL) as methods for training teacher models that are later merged into a single student via on‑policy distillation (OPD). Across agentic, reasoning, and perception tasks, RL‑trained teachers produce stronger students and better recover teacher performance gains than SFT teachers, both in single‑teacher and multi‑teacher OPD settings. Analysis shows RL teachers deviate less from the shared initialization, leading to faster and higher overlap in teacher–student top‑K predictions, which appears to facilitate more effective OPD learning.

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