arXiv:2605.08283cs.LGcs.AI2026-05

通过分层控制生成令牌,实现推理中探索与利用的更好平衡。

HTPO: Towards Exploration-Exploitation Balanced Policy Optimization via Hierarchical Token-level Objective Control

论文配图:HTPO: Towards Exploration-Exploitation Balanced Policy Optimization via Hierarchical Token-level Objective Control
图 1 · 摘自论文原文
  • 将响应令牌按功能分组,分层设计优化目标
  • 在AIME'24/25上比DAPO提升8.6%和6.7%
  • 适合需要精细推理控制的大型语言模型研究

基于可验证奖励的强化学习(RLVR)已成为提升大语言模型(LLMs)推理能力的关键技术。然而,主流强化学习算法对单个响应中的所有令牌一视同仁,赋予相同优化目标,无法为推理过程提供细粒度指导。在思维链(CoT)推理中,不同令牌通常承担不同角色。因此,现有算法缺乏在学习过程中动态平衡探索与利用的有效机制。为此,我们提出分层令牌级目标控制策略优化(HTPO),采用分而治之思想,从提示难度、答案正确性、令牌熵三个维度将响应令牌划分为特定功能组。在每组内,根据其对探索或利用的贡献,设计专用优化目标,以促进各令牌预期功能的有效执行。这样,HTPO可实现更均衡的探索-利用权衡。在多个挑战性推理基准上的实验表明,该算法显著优于强基线DAPO(如在AIME'24和AIME'25上分别提升8.6%和6.7%)。在测试时计算量扩大时,HTPO训练模型持续保持优势,且差距随采样预算增加而扩大,验证了自适应令牌级控制方法在不牺牲利用性能的前提下促进有效探索的能力。代码将发布于https://github.com/xcyao00/HTPO。

原文摘要 · Abstract (English)

Reinforcement Learning with Verifiable Rewards (RLVR) has emerged as a pivotal technique for enhancing the reasoning capabilities of Large Language Models (LLMs). However, the de facto practice of mainstream RL algorithms is to treat all tokens of one response equally and assign the same optimization objective to each token, failing to provide granular guidance for the reasoning process. While in Chain-of-Thought (CoT) reasoning, different tokens usually play distinct roles. Therefore, the current RL algorithms lack an effective mechanism to dynamically balance the exploration-exploitation trade-off during learning. To this end, we propose Hierarchical Token-level Objective Control Policy Optimization (HTPO), a novel RL algorithm that takes the divide-and-conquer idea to hierarchically partition the response tokens into specific functional groups from three aspects (i.e., prompt difficulty, answer correctness, and token entropy). Within each group, according to the contributions to exploration or exploitation, we design specialized optimization objectives to facilitate the effective execution of each token's expected functionality. In this way, HTPO can achieve a more balanced exploration-exploitation trade-off. Extensive experiments on challenging reasoning benchmarks validate the superiority of our HTPO algorithm, which significantly outperforms the strong DAPO baseline (e.g., +8.6% and +6.7% on AIME'24 and AIME'25, respectively). When scaling test-time compute, the HTPO-trained model maintains a consistent performance advantage over the DAPO baseline, and the gap widens as the sampling budget increases, validating that our adaptive token-level control method fosters effective exploration without sacrificing exploitation performance. Code will be at https://github.com/xcyao00/HTPO.

强化学习推理增强令牌控制

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