Topology of Reasoning: Understanding Large Reasoning Models through Reasoning Graph Properties

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Main Authors: Minegishi, Gouki, Furuta, Hiroki, Kojima, Takeshi, Iwasawa, Yusuke, Matsuo, Yutaka
Format: Preprint
Published: 2025
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author Minegishi, Gouki
Furuta, Hiroki
Kojima, Takeshi
Iwasawa, Yusuke
Matsuo, Yutaka
author_facet Minegishi, Gouki
Furuta, Hiroki
Kojima, Takeshi
Iwasawa, Yusuke
Matsuo, Yutaka
contents Recent large-scale reasoning models have achieved state-of-the-art performance on challenging mathematical benchmarks, yet the internal mechanisms underlying their success remain poorly understood. In this work, we introduce the notion of a reasoning graph, extracted by clustering hidden-state representations at each reasoning step, and systematically analyze three key graph-theoretic properties: cyclicity, diameter, and small-world index, across multiple tasks (GSM8K, MATH500, AIME 2024). Our findings reveal that distilled reasoning models (e.g., DeepSeek-R1-Distill-Qwen-32B) exhibit significantly more recurrent cycles (about 5 per sample), substantially larger graph diameters, and pronounced small-world characteristics (about 6x) compared to their base counterparts. Notably, these structural advantages grow with task difficulty and model capacity, with cycle detection peaking at the 14B scale and exploration diameter maximized in the 32B variant, correlating positively with accuracy. Furthermore, we show that supervised fine-tuning on an improved dataset systematically expands reasoning graph diameters in tandem with performance gains, offering concrete guidelines for dataset design aimed at boosting reasoning capabilities. By bridging theoretical insights into reasoning graph structures with practical recommendations for data construction, our work advances both the interpretability and the efficacy of large reasoning models.
format Preprint
id arxiv_https___arxiv_org_abs_2506_05744
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Topology of Reasoning: Understanding Large Reasoning Models through Reasoning Graph Properties
Minegishi, Gouki
Furuta, Hiroki
Kojima, Takeshi
Iwasawa, Yusuke
Matsuo, Yutaka
Artificial Intelligence
Recent large-scale reasoning models have achieved state-of-the-art performance on challenging mathematical benchmarks, yet the internal mechanisms underlying their success remain poorly understood. In this work, we introduce the notion of a reasoning graph, extracted by clustering hidden-state representations at each reasoning step, and systematically analyze three key graph-theoretic properties: cyclicity, diameter, and small-world index, across multiple tasks (GSM8K, MATH500, AIME 2024). Our findings reveal that distilled reasoning models (e.g., DeepSeek-R1-Distill-Qwen-32B) exhibit significantly more recurrent cycles (about 5 per sample), substantially larger graph diameters, and pronounced small-world characteristics (about 6x) compared to their base counterparts. Notably, these structural advantages grow with task difficulty and model capacity, with cycle detection peaking at the 14B scale and exploration diameter maximized in the 32B variant, correlating positively with accuracy. Furthermore, we show that supervised fine-tuning on an improved dataset systematically expands reasoning graph diameters in tandem with performance gains, offering concrete guidelines for dataset design aimed at boosting reasoning capabilities. By bridging theoretical insights into reasoning graph structures with practical recommendations for data construction, our work advances both the interpretability and the efficacy of large reasoning models.
title Topology of Reasoning: Understanding Large Reasoning Models through Reasoning Graph Properties
topic Artificial Intelligence
url https://arxiv.org/abs/2506.05744