Exploring the Potential of Offline RL for Reasoning in LLMs: A Preliminary Study
Xiaoyu Tian, Sitong Zhao, Haotian Wang, Shuaiting Chen, Yiping Peng, Yunjie Ji, Han Zhao, Xiangang Li
TL;DR
This paper examines offline reinforcement learning for enhancing long-context reasoning in large language models using LD-DPO. It demonstrates that LD-DPO yields consistent improvements across math, code generation, instruction-following, and general reasoning benchmarks, with average gains around 3.3% and notable Arena-Hard gains of 10.1%. The authors analyze the length-sensitivity of DPO and show that length-desensitized LD-DPO can produce concise, semantically rich outputs while boosting performance. They discuss future directions for additional offline methods and hybrid offline-online training to reduce cost and scale reasoning abilities.
Abstract
Despite significant advances in long-context reasoning by large language models (LLMs), primarily through Online Reinforcement Learning (RL) methods, these approaches incur substantial computational costs and complexity. In contrast, simpler and more economical Offline RL methods remain underexplored. To address this gap, we investigate the effectiveness of Offline RL methods, specifically Direct Preference Optimization (DPO) and its length-desensitized variant LD-DPO, in enhancing the reasoning capabilities of LLMs. Extensive experiments across multiple reasoning benchmarks demonstrate that these simpler Offline RL methods substantially improve model performance, achieving an average enhancement of 3.3\%, with a particularly notable increase of 10.1\% on the challenging Arena-Hard benchmark. Furthermore, we analyze DPO's sensitivity to output length, emphasizing that increasing reasoning length should align with semantic richness, as indiscriminate lengthening may adversely affect model performance. We provide comprehensive descriptions of our data processing and training methodologies, offering empirical evidence and practical insights for developing more cost-effective Offline RL approaches.
