English

Quantile Reward Policy Optimization: Alignment with Pointwise Regression and Exact Partition Functions

Machine Learning 2025-12-02 v2

Abstract

Aligning large language models with pointwise absolute rewards has so far required online, on-policy algorithms such as PPO and GRPO. In contrast, simpler methods that can leverage offline or off-policy data, such as DPO and REBEL, are limited to learning from preference pairs or relative signals. To bridge this gap, we introduce Quantile Reward Policy Optimization (QRPO), which learns from pointwise absolute rewards while preserving the simplicity and offline applicability of DPO-like methods. QRPO uses quantile rewards to enable regression to the closed-form solution of the KL-regularized RL objective. This reward yields an analytically tractable partition function, removing the need for relative signals to cancel this term. Moreover, QRPO scales with increased compute to estimate quantile rewards, opening a new dimension for pre-computation scaling. Empirically, QRPO consistently achieves top performance on chat and coding evaluations--reward model scores, AlpacaEval 2, and LeetCode--compared to DPO, REBEL, and SimPO across diverse datasets and 8B-scale models. Finally, we find that training with robust rewards instead of converting them to preferences induces less length bias.

Keywords

Cite

@article{arxiv.2507.08068,
  title  = {Quantile Reward Policy Optimization: Alignment with Pointwise Regression and Exact Partition Functions},
  author = {Simon Matrenok and Skander Moalla and Caglar Gulcehre},
  journal= {arXiv preprint arXiv:2507.08068},
  year   = {2025}
}

Comments

58 pages, NeurIPS2025 camera-ready version

R2 v1 2026-07-01T03:55:23.682Z