arXiv:2606.19771cs.AI2026-06

通过分析词元分布差异,提升大模型推理的稳定性和准确性

Beyond Entropy: Learning from Token-Level Distributional Deviations for LLM Reasoning

论文配图:Beyond Entropy: Learning from Token-Level Distributional Deviations for LLM Reasoning
图 1 · 摘自论文原文
  • 聚焦词元分布特性,用JS散度识别关键决策点
  • 仅更新前10%独特词元,平均准确率提升4.58%
  • 适合追求推理稳定性与效率的LLM研究者

强化学习结合可验证奖励(RLVR)显著推动了大语言模型(LLM)推理的发展;然而其面临根本性优化不稳定性:均匀更新词元导致熵坍缩,引发过早收敛至次优策略;过度最大化香农熵则造成熵爆炸,引发无意义探索。为此,我们提出独立组合词元(ICT)框架,将优化重点从标量不确定性转向词元logits的分布特性。通过计算词元logits分布间的Jensen-Shannon(JS)散度,ICT识别出具有显著分布模式的词元作为引导有效探索的关键分支点。理论分析基于香农熵与二阶Rényi熵,证明选择性更新这些词元可调节策略集中度:降低香农熵衡量的整体分布不确定性,同时控制Rényi熵反映的概率集中程度。这一双重效应防止过度集中生成削弱探索,有效稳定训练过程。实证结果表明,在Qwen2.5(0.5B/1.5B/7B)模型上仅更新前10%独特词元,跨七项基准(涵盖数学、常识与奥数级问题)平均pass@4提升4.58%,最高达14.9%,优于GRPO、20-Entropy与STAPO基线。

原文摘要 · Abstract (English)

Reinforcement Learning with Verifiable Rewards (RLVR) has significantly advanced Large Language Model (LLM) reasoning; however, it faces a fundamental optimization instability: uniform token updates precipitate entropy collapse, leading to premature convergence to suboptimal strategies, whereas excessive Shannon Entropy maximization can cause entropy explosion, driving blind exploration toward incoherent reasoning chains. To resolve this dichotomy, we introduce the Independent Combinatorial Tokens (ICT) framework, which shifts the optimization focus from scalar uncertainty to the distributional properties of token logits. By leveraging the Jensen-Shannon (JS) divergence between token logits distributions, ICT identifies tokens with distinctive distributional patterns as critical branching points for guiding effective exploration in LLM reasoning. Our theoretical analysis, grounded in both Shannon and second-order Rényi entropy, proves that selectively updating on these tokens regulates policy concentration: it reduces the overall distribution uncertainty measured by Shannon entropy, while controlling probability concentration captured by second-order Rényi entropy. This dual effect prevents over-concentrated token generation from weakening exploration and effectively stabilizes the training landscape. Empirical results demonstrate that updating only the top 10% of unique tokens on Qwen2.5 (0.5B/1.5B/7B) models yields an average pass@4 improvement of 4.58%, with a maximum gain of 14.9%, over GRPO, 20-Entropy, and STAPO baselines across seven benchmarks spanning math, commonsense, and Olympiad-level problems.

大模型推理强化学习熵控制词元分析

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