O1-Pruner: Length-Harmonizing Fine-Tuning for O1-Like Reasoning Pruning
Authors: name: Haotian Luo, name: Li Shen, name: Haiying He, name: Yibo Wang, name: Shiwei Liu, name: Wei Li, name: Naiqiang Tan, name: Xiaochun Cao, name: Dacheng Tao

Recently, long-thought reasoning LLMs, such as OpenAI's O1, adopt extended
reasoning processes similar to how humans ponder over complex problems. This
reasoning paradigm significantly enhances the model's problem-solving abilities
and has achieved promising results. However, long-thought reasoning process
leads to a substantial increase in inference time. A pressing challenge is
reducing the inference overhead of long-thought LLMs while ensuring accuracy.
In this paper, we experimentally demonstrate that long-thought reasoning models
struggle to effectively allocate token budgets based on problem difficulty and
reasoning redundancies. To address this, we propose Length-Harmonizing
Fine-Tuning (O1-Pruner), aiming at minimizing reasoning overhead while
maintaining accuracy. This effective fine-tuning method first estimates the
LLM's baseline performance through pre-sampling and then uses RL-style
fine-tuning to encourage the model to generate shorter reasoning processes
under accuracy constraints. This allows the model to achieve efficient
reasoning with lower redundancy while maintaining accuracy. Experiments on
various mathematical reasoning benchmarks show that O1-Pruner not only
significantly reduces inference overhead but also achieves higher accuracy,
providing a novel and promising solution to this challenge. Our code is coming
soon at https://github.com/StarDewXXX/O1-Pruner