Efficient Long CoT Reasoning in Small Language Models

Fuente: arXiv
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Main Authors: Wang, Zhaoyang, Jiang, Jinqi, Qiu, Tian, Liu, Hui, Tang, Xianfeng, Yao, Huaxiu
Format: Preprint
Published: 2025
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author Wang, Zhaoyang
Jiang, Jinqi
Qiu, Tian
Liu, Hui
Tang, Xianfeng
Yao, Huaxiu
author_facet Wang, Zhaoyang
Jiang, Jinqi
Qiu, Tian
Liu, Hui
Tang, Xianfeng
Yao, Huaxiu
contents Recent large reasoning models such as DeepSeek-R1 exhibit strong complex problems solving abilities by generating long chain-of-thought (CoT) reasoning steps. It is challenging to directly train small language models (SLMs) to emerge long CoT. Thus, distillation becomes a practical method to enable SLMs for such reasoning ability. However, the long CoT often contains a lot of redundant contents (e.g., overthinking steps) which may make SLMs hard to learn considering their relatively poor capacity and generalization. To address this issue, we propose a simple-yet-effective method to prune unnecessary steps in long CoT, and then employ an on-policy method for the SLM itself to curate valid and useful long CoT training data. In this way, SLMs can effectively learn efficient long CoT reasoning and preserve competitive performance at the same time. Experimental results across a series of mathematical reasoning benchmarks demonstrate the effectiveness of the proposed method in distilling long CoT reasoning ability into SLMs which maintains the competitive performance but significantly reduces generating redundant reasoning steps.
format Preprint
id arxiv_https___arxiv_org_abs_2505_18440
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Efficient Long CoT Reasoning in Small Language Models
Wang, Zhaoyang
Jiang, Jinqi
Qiu, Tian
Liu, Hui
Tang, Xianfeng
Yao, Huaxiu
Computation and Language
Artificial Intelligence
Recent large reasoning models such as DeepSeek-R1 exhibit strong complex problems solving abilities by generating long chain-of-thought (CoT) reasoning steps. It is challenging to directly train small language models (SLMs) to emerge long CoT. Thus, distillation becomes a practical method to enable SLMs for such reasoning ability. However, the long CoT often contains a lot of redundant contents (e.g., overthinking steps) which may make SLMs hard to learn considering their relatively poor capacity and generalization. To address this issue, we propose a simple-yet-effective method to prune unnecessary steps in long CoT, and then employ an on-policy method for the SLM itself to curate valid and useful long CoT training data. In this way, SLMs can effectively learn efficient long CoT reasoning and preserve competitive performance at the same time. Experimental results across a series of mathematical reasoning benchmarks demonstrate the effectiveness of the proposed method in distilling long CoT reasoning ability into SLMs which maintains the competitive performance but significantly reduces generating redundant reasoning steps.
title Efficient Long CoT Reasoning in Small Language Models
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2505.18440