arXiv:2509.25598cs.AIcs.LG2025-09被引 10

提出混合奖励归一化方法,提升非可验证任务中大模型的推理能力。

Hybrid Reward Normalization for Process-supervised Non-verifiable Agentic Tasks

  • 基于原则的奖励模型实现步骤级评估,增强过程判断透明性。
  • 引入奖励归一化策略,平衡过程奖励与最终结果之间的关系。
  • 在多个基准上表现领先,适合复杂推理任务的研究者参考。

大型语言模型(LLMs)越来越多地依赖外部工具(如搜索引擎)解决需要推理和外部知识检索的复杂智能体任务。近期,基于可验证奖励的强化学习(RLVR)通过最终答案的奖励信号有效提升了LLM的能力。然而,结果奖励仅提供稀疏且延迟的反馈,难以用于长轨迹任务。过程奖励通过评估中间步骤,提供细粒度监督并鼓励基于事实的问题求解。但步骤级标注尤其在无“黄金标准”答案的非可验证任务中极难实现。此外,需平衡局部质量与对最终结果的贡献,因单纯优化过程奖励未必带来更好结果。为此,本文提出原则性过程奖励(PPR),一种统一原则化步骤评估与结果验证的强化学习方法。训练一个基于原则的奖励模型以提升过程评估的透明性与可靠性,并进一步引入奖励归一化(ReNorm)策略校准结果奖励与过程奖励。实验表明,PPR在多种基准上达到当前最优性能,展现出卓越的鲁棒性与泛化能力。代码与模型已公开。

原文摘要 · Abstract (English)

Large Language Models (LLMs) increasingly rely on external tools such as search engines to solve complex agentic tasks that require reasoning and external knowledge retrieval. Recently, reinforcement learning with verifiable rewards (RLVR) has demonstrated its effectiveness in advancing capabilities of LLMs by rewarding the final answers via outcome rewards. While straightforward to supervise, outcome rewards only provide sparse signals and delayed feedback, which limits their effectiveness on long trajectories. Process rewards address this by evaluating intermediate steps, providing fine-grained supervision and encouraging grounded problem solving. However, it is notoriously hard to annotate step-wise labels, especially in non-verifiable process without "golden" answers. Furthermore, step-wise judgment requires the balance between local quality with contribution to the final outcome, as optimizing towards higher process reward may not always align with better final outcomes. To address the above challenges, we introduce Principle Process Reward (PPR), an RL approach that unifies principled step-level assessment and outcome verification. We train a principle-based reward model to improve the transparency and reliability of process evaluation, and further introduce a Reward Normalization (ReNorm) strategy to calibrate outcome and process rewards. Experiment results show that PPR achieves state-of-the-art performance across a wide range of benchmarks, demonstrating its impressive robustness and generalization. Our code and model collection is available in this link.

强化学习大模型奖励设计推理任务

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