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Advantage-based on-policy distillation weights teacher actions by what actually helps the student, using only the rollouts it was already running

AspireAI community · arXiv
Online policy distillation usually trains the student to follow the teacher at every state of the trajectory, on the assumption that teacher guidance is always beneficial. Advantage-Based On-Policy Distillation instead separates what the teacher prefers from what helps the current student succeed, weighting teacher actions by their counterfactual advantage under the student and downweighting those that do not help. The obstacle is that computing those advantages directly would require trying alternative teacher actions at each step and running new rollouts from each. The paper shows the AOPD objective can instead be estimated from standard student rollouts and their terminal rewards alone, using teacher importance weights on student-sampled actions to give unbiased advantage-weighted supervision with no extra rollouts or reward evaluations, and reports gains over distillation and RL baselines on math, coding and MedQA in both external-teacher and self-distillation settings. The abstract reports gains without a single headline margin, and the paper is a preprint.
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