Enhancing Math Reasoning in Small-sized LLMs via Preview Difficulty-Aware Intervention

Reinforcement learning scaling enhances the reasoning capabilities of large language models, with reinforcement learning serving as the key technique to draw out complex reasoning. However, key technical details of state-of-the-art reasoning LLMs—such as those in the OpenAI O series, Claude 3 series, DeepMind’s Gemini 2.5 series, and Grok 3 series—remain undisclosed, making it difficult for the research community to replicate their reinforcement learning training results. Therefore, we start our study from an Early Preview Reinforcement Learning (EPRLI) algorithm built on the open-source GRPO framework, incorporating difficulty-aware intervention for math problems. Applied to a $1.5B$-parameter LLM, our method achieves 50.0\% on AIME24, 89.2\% on Math500, 77.1\% on AMC, 35.3\% on Minerva and 51.9\% on OBench—superpass O1-Preview and is comparable to O1-mini within standard lab settings.