重构大模型推理的奖励设计,让强化学习更可靠
Reward Modeling for Reinforcement Learning-Based LLM Reasoning: Design, Challenges, and Evaluation
- 提出面向推理的奖励建模框架RARL,系统分类多种奖励机制
- 揭示奖励欺骗是导致幻觉和泛化失败的核心问题
- 适合关注大模型推理对齐与评估可信性的研究者
大型语言模型(LLMs)具有变革性潜力,但其推理过程仍不稳定且不可靠。基于强化学习(RL)的微调是提升性能的关键方法,但其效果本质上由奖励设计决定。尽管重要,奖励建模与核心挑战(如评估偏差、幻觉、分布偏移、高效学习)之间的关系仍不清晰。本文认为,奖励建模不仅是实现细节,更是推理对齐的核心架构,塑造模型学习内容、泛化能力及输出可信度。我们提出推理对齐强化学习(RARL),一种以推理为中心的分类视角,梳理多步推理中的多样化奖励范式。在此框架下,构建奖励机制分类体系,分析奖励欺骗这一普遍失效模式,并探讨奖励信号如何统一应对从推理时扩展到幻觉缓解等挑战。进一步批判性评估现有基准,揭示数据污染与奖励错位等漏洞,并提出更稳健评估的方向。通过整合分散的研究线索,厘清奖励设计与根本推理能力的相互作用,为构建鲁棒、可验证、可信的大模型推理系统提供基础路线图。
原文摘要 · Abstract (English)
Large Language Models (LLMs) demonstrate transformative potential, yet their reasoning remains inconsistent and unreliable. Reinforcement learning (RL)-based fine-tuning is a key mechanism for improvement, but its effectiveness is fundamentally governed by reward design. Despite its importance, the relationship between reward modeling and core LLM challenges--such as evaluation bias, hallucination, distribution shift, and efficient learning--remains poorly understood. This work argues that reward modeling is not merely an implementation detail but a central architect of reasoning alignment, shaping what models learn, how they generalize, and whether their outputs can be trusted. We introduce Reasoning-Aligned Reinforcement Learning (RARL), a reasoning-centric taxonomic perspective that organizes diverse reward paradigms for multi-step reasoning. Within this perspective, we present a taxonomy of reward mechanisms, analyze reward hacking as a pervasive failure mode, and examine how reward signals unify challenges ranging from inference-time scaling to hallucination mitigation. We further critically evaluate existing benchmarks, highlighting vulnerabilities such as data contamination and reward misalignment, and outline directions for more robust evaluation. By integrating fragmented research threads and clarifying the interplay between reward design and fundamental reasoning capabilities, this work provides a foundational roadmap for building reasoning models that are robust, verifiable, and trustworthy.
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