Beyond Accuracy: Diagnosing Algebraic Reasoning Failures in LLMs Across Nine Complexity Dimensions

Parth Shrikant Patil, Yash Sinha, Murari Mandal, Dhruv Kumar


Abstract
Aggregate mathematical accuracy does not usually identify the source of a model failure. In algebraic reasoning, errors may arise from nesting depth, operator identity, simultaneous intermediate values, branch-local composition, repeated-token counting, sequential dependence, or numeric magnitude. We introduce a nine-dimension algebraic complexity framework that converts these factors into controlled diagnostic variables. For each dimension, a parametric generator increases one target variable while holding the remaining variables at minimum values. Every retained problem is verified by a computer algebra system. We evaluate eight models, including six standard instruction- tuned models and two reasoning-specialised models. The results show that standard models exhibit a scale-limited D4 working-memory collapse in the 20–40 parallel-branch region. Notably, Qwen3 235B does not escape the transition band observed for Llama 3 8B, despite its much larger parameter scale. Reasoning- specialised models shift this limit to higher levels, but they do not remove it. D5 branch-local composition and D7 repeated-token counting produce distinct failures that are not reducible to aggregate length or depth.
Anthology ID:
2026.mathnlp-main.17
Volume:
The Proceedings of the 4th Workshop on Mathematical Natural Language Processing (MathNLP 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Marco Valentino, Deborah Ferreira, Mokanarangan Thayaparan, Leonardo Ranaldi, Jo-Ku Cheng, Andre Freitas
Venues:
MathNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
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Pages:
216–239
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URL:
https://aclanthology.org/2026.mathnlp-main.17/
DOI:
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Cite (ACL):
Parth Shrikant Patil, Yash Sinha, Murari Mandal, and Dhruv Kumar. 2026. Beyond Accuracy: Diagnosing Algebraic Reasoning Failures in LLMs Across Nine Complexity Dimensions. In The Proceedings of the 4th Workshop on Mathematical Natural Language Processing (MathNLP 2026), pages 216–239, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond Accuracy: Diagnosing Algebraic Reasoning Failures in LLMs Across Nine Complexity Dimensions (Patil et al., MathNLP 2026)
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https://aclanthology.org/2026.mathnlp-main.17.pdf