ReasonBENCH: Benchmarking the (In)Stability of LLM Reasoning

Fuente: arXiv
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Hauptverfasser: Potamitis, Nearchos, Ramani, Vansh, Arora, Har Ashish, Kuchhal, Dhairya, Klein, Lars, Arora, Akhil
Format: Preprint
Veröffentlicht: 2025
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author Potamitis, Nearchos
Ramani, Vansh
Arora, Har Ashish
Kuchhal, Dhairya
Klein, Lars
Arora, Akhil
author_facet Potamitis, Nearchos
Ramani, Vansh
Arora, Har Ashish
Kuchhal, Dhairya
Klein, Lars
Arora, Akhil
contents Benchmark scores for LLM reasoning systems are reported as single numbers, yet the same model, strategy, and task can produce meaningfully different answers and costs across repeated executions, even under greedy decoding (T = 0). This variance is not a statistical nuisance: the highest-performing strategy wins only 77% of head-to-head runs against its nearest competitor, meaning a single observed score can silently misrank systems. We introduce ReasonBench, a benchmark suite recording 30 independent trials across 10 reasoning strategies, 12 models, and 6 tasks, treating quality and cost as distributions rather than point estimates. We find that this variance is structured rather than random: a two-component taxonomy -- Global Noise, capturing cross-benchmark unevenness, and Run Noise, capturing within-benchmark stochasticity -- reveals that strategy architecture predicts stability profiles, while models and strategies shift orthogonal aspects of the distribution. A hierarchical decomposition attributes three-quarters of score variance to benchmark, system, and item structure, with a persistent residual that single-run evaluation silently absorbs. Finally, cost and quality decouple asymmetrically: cheap methods are structurally immune to joint cost-quality failure, while expensive methods remain exposed regardless of their accuracy. These findings establish instability as an inherent property of reasoning systems and motivate distribution-aware evaluation as standard practice.
format Preprint
id arxiv_https___arxiv_org_abs_2512_07795
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle ReasonBENCH: Benchmarking the (In)Stability of LLM Reasoning
Potamitis, Nearchos
Ramani, Vansh
Arora, Har Ashish
Kuchhal, Dhairya
Klein, Lars
Arora, Akhil
Artificial Intelligence
Computation and Language
Machine Learning
Benchmark scores for LLM reasoning systems are reported as single numbers, yet the same model, strategy, and task can produce meaningfully different answers and costs across repeated executions, even under greedy decoding (T = 0). This variance is not a statistical nuisance: the highest-performing strategy wins only 77% of head-to-head runs against its nearest competitor, meaning a single observed score can silently misrank systems. We introduce ReasonBench, a benchmark suite recording 30 independent trials across 10 reasoning strategies, 12 models, and 6 tasks, treating quality and cost as distributions rather than point estimates. We find that this variance is structured rather than random: a two-component taxonomy -- Global Noise, capturing cross-benchmark unevenness, and Run Noise, capturing within-benchmark stochasticity -- reveals that strategy architecture predicts stability profiles, while models and strategies shift orthogonal aspects of the distribution. A hierarchical decomposition attributes three-quarters of score variance to benchmark, system, and item structure, with a persistent residual that single-run evaluation silently absorbs. Finally, cost and quality decouple asymmetrically: cheap methods are structurally immune to joint cost-quality failure, while expensive methods remain exposed regardless of their accuracy. These findings establish instability as an inherent property of reasoning systems and motivate distribution-aware evaluation as standard practice.
title ReasonBENCH: Benchmarking the (In)Stability of LLM Reasoning
topic Artificial Intelligence
Computation and Language
Machine Learning
url https://arxiv.org/abs/2512.07795