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arXiv 2603.12554cs.LGcs.AIcs.CL
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基于熵引导的步骤选择和分步优势的扩散语言模型强化学习

Reinforcement Learning for Diffusion LLMs with Entropy-Guided Step Selection and Stepwise Advantages

Department of Electrical & Computer Engineering(电气与计算机工程系)

Vishnu Teja Kunde, Fatemeh Doudi, Mahdi Farahbakhsh, Dileep Kalathil, Krishna Narayanan, Jean-Francois Chamberland

AI总结:

本文提出一种针对扩散语言模型的强化学习方法,通过熵引导选择步骤和分步优势估计,实现无偏策略梯度,提升生成效果和计算效率。

摘要:

强化学习(RL)在训练后自回归语言模型中表现出色,但将其扩展到扩散语言模型(DLMs)具有挑战性,因为序列级似然不可计算。现有方法依赖于替代似然或启发式近似,可能引入偏差并模糊去噪的序列结构。我们把基于扩散的序列生成视为一个有限时间范围的马尔可夫决策过程,推导出一个精确、无偏的策略梯度,将其分解为去噪步骤,并以中间优势表示,而无需显式评估序列似然。为了获得实用且计算高效的估计器,我们(i)通过熵引导的近似界选择去噪步骤用于策略更新,(ii)利用扩散模型自然提供的一步去噪奖励估计中间优势,避免了昂贵的多步回放。在编码和逻辑推理基准上的实验表明,取得了最先进的结果,对数学推理表现出强劲的竞争力,优于现有RL后训练方法用于DLMs。代码可在https://github.com/vishnutez/egspo-dllm-rl获取。

英文摘要:

Reinforcement learning (RL) has been effective for post-training autoregressive (AR) language models, but extending these methods to diffusion language models (DLMs) is challenging due to intractable sequence-level likelihoods. Existing approaches therefore rely on surrogate likelihoods or heuristic approximations, which can introduce bias and obscure the sequential structure of denoising. We formulate diffusion-based sequence generation as a finite-horizon Markov decision process over the denoising trajectory and derive an exact, unbiased policy gradient that decomposes over denoising steps and is expressed in terms of intermediate advantages, without requiring explicit evaluation of the sequence likelihood. To obtain a practical and compute-efficient estimator, we (i) select denoising steps for policy updates via an entropy-guided approximation bound, and (ii) estimate intermediate advantages using a one-step denoising reward naturally provided by the diffusion model, avoiding costly multi-step rollouts. Experiments on coding and logical reasoning benchmarks demonstrate state-of-the-art results, with strong competitive performance on mathematical reasoning, outperforming existing RL post-training approaches for DLMs. Code is available at https://github.com/vishnutez/egspo-dllm-rl.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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