OPT-Engine: Benchmarking the Limits of LLMs in Optimization Modeling via Complexity Scaling
Pith reviewed 2026-05-16 16:15 UTC · model grok-4.3
The pith
Solver-integrated LLMs for optimization modeling are limited primarily by errors in automated constraint formulation as problem complexity scales.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
For the current solver-integrated reasoning paradigm, the automated formulation of constraints represents the primary bottleneck in LLM performance on optimization modeling tasks.
What carries the argument
OPT-Engine benchmark that scales ten canonical problems by number of variables, number of constraints, and degree of integrality to create measurable difficulty levels.
Load-bearing premise
The ten chosen canonical problems together with the metrics of variable count, constraint count, and integrality level are representative of the optimization modeling tasks LLMs will face.
What would settle it
An LLM that produces error-free constraint formulations for the highest-complexity mixed-integer instances in the benchmark while using solver integration would disprove the claim that constraint formulation is the dominant limit.
Figures
read the original abstract
We investigate the capabilities and scalability of Large Language Models (LLMs) in optimization modeling, a domain requiring structured reasoning and precise formulation. To this end, we introduce OPT-ENGINE, an extensible benchmark framework with quantifiable and controllable complexity. OPT-ENGINE spans ten canonical Operations Research problems, systematically scaling from Linear Programming to Mixed-Integer Programming, providing a structured environment to probe the limits of automated problem formulation and solving. Utilizing OPT-Engine, we address three pivotal research questions. First, we examine whether Pure-Text Reasoning (PTR) via classical Chain-of-Thought can efficiently tackle optimization tasks, finding that PTR suffers from a critical robustness gap as task complexity increases. Second, we examine whether integrating external computational tools can mitigate PTR's arithmetic weaknesses and improve performance. Our results indicate that while such tools help with local calculations, they still fail to adhere to global optimization constraints. Finally, we pinpoint that for the current SOTA paradigm, Solver-integrated Reasoning (SIR), the automated formulation of constraints represents the primary bottleneck. These findings clarify the limitations of current paradigms and provide a structured roadmap for developing next-generation LLMs for optimization modeling. We release our code and data to facilitate future research (https://github.com/Cardinal-Operations/OPTEngine).
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces OPT-ENGINE, an extensible benchmark spanning ten canonical Operations Research problems with controllable complexity scaling from Linear Programming to Mixed-Integer Programming. It evaluates three paradigms—Pure-Text Reasoning (PTR) via Chain-of-Thought, tool-integrated reasoning, and Solver-integrated Reasoning (SIR)—reporting that PTR exhibits a robustness gap with increasing complexity, external tools mitigate only local arithmetic errors, and constraint formulation is the primary bottleneck for SIR.
Significance. If the empirical trends hold, the work supplies a reproducible framework and concrete failure-mode analysis for LLM-based optimization modeling, with the public code release enabling direct verification and extension. The scoped conclusions on paradigm-specific bottlenecks offer a practical roadmap without overclaiming universality.
major comments (1)
- [Experimental results] Experimental results section: the reported robustness gaps and bottleneck attributions for SIR lack accompanying error bars, statistical tests, or exact prompt templates, making it difficult to confirm that post-hoc filtering or prompt choices do not influence the primary claim that constraint formulation is the dominant failure mode.
minor comments (2)
- [Methods] Methods section: the precise definitions and formulas for the complexity scaling metrics (number of variables, constraints, integrality) should be stated explicitly with an example instance to allow readers to replicate the scaling procedure.
- [Figures] Figure captions: several performance plots would benefit from clearer legends distinguishing the three paradigms and from annotation of the exact complexity levels at which the robustness gap becomes statistically noticeable.
Simulated Author's Rebuttal
We thank the referee for the positive assessment, the recommendation of minor revision, and the constructive comment on experimental rigor. We address the single major comment below.
read point-by-point responses
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Referee: Experimental results section: the reported robustness gaps and bottleneck attributions for SIR lack accompanying error bars, statistical tests, or exact prompt templates, making it difficult to confirm that post-hoc filtering or prompt choices do not influence the primary claim that constraint formulation is the dominant failure mode.
Authors: We agree that the current presentation would benefit from greater statistical transparency. In the revised manuscript we will add error bars (standard deviation over five independent runs) to all key performance metrics, include statistical significance tests (paired t-tests and bootstrap confidence intervals) to support the reported robustness gaps, and provide the complete prompt templates together with any post-processing rules in a new appendix. These additions will allow readers to verify that the constraint-formulation bottleneck remains the dominant failure mode independent of prompt variation or post-hoc filtering. revision: yes
Circularity Check
No significant circularity; empirical observations from benchmark experiments
full rationale
The paper introduces the OPT-ENGINE benchmark spanning ten canonical OR problems with controllable complexity scaling and reports direct empirical results on PTR, tool integration, and SIR paradigms. The key claim that constraint formulation is the primary bottleneck for SIR follows from observed performance gaps and robustness failures in the experiments, without any reduction to self-defined quantities, fitted parameters renamed as predictions, or load-bearing self-citations. The derivation chain consists of benchmark construction followed by experimental measurement, which is self-contained and externally verifiable via the released code.
Axiom & Free-Parameter Ledger
Forward citations
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Reference graph
Works this paper leans on
-
[1]
Josh Achiam, Steven Adler, Sandhini Agarwal, Lama Ahmad, Ilge Akkaya, Florencia Leoni Aleman, Diogo Almeida, Janko Altenschmidt, Sam Altman, Shyamal Anadkat, et al. Gpt-4 technical report. arXiv preprint arXiv:2303.08774, 2023
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[2]
Gemini: A Family of Highly Capable Multimodal Models
Gemini Team, Rohan Anil, Sebastian Borgeaud, Jean-Baptiste Alayrac, Jiahui Yu, Radu Soricut, Johan Schalkwyk, Andrew M Dai, Anja Hauth, Katie Millican, et al. Gemini: a family of highly capable multimodal models.arXiv preprint arXiv:2312.11805, 2023
work page internal anchor Pith review Pith/arXiv arXiv 2023
-
[3]
Gemini 1.5: Unlocking multimodal understanding across millions of tokens of context
Gemini Team, Petko Georgiev, Ving Ian Lei, Ryan Burnell, Libin Bai, Anmol Gulati, Garrett Tanzer, Damien Vincent, Zhufeng Pan, Shibo Wang, et al. Gemini 1.5: Unlocking multimodal understanding across millions of tokens of context.arXiv preprint arXiv:2403.05530, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[4]
Aixin Liu, Bei Feng, Bing Xue, Bingxuan Wang, Bochao Wu, Chengda Lu, Chenggang Zhao, Chengqi Deng, Chenyu Zhang, Chong Ruan, et al. Deepseek-v3 technical report.arXiv preprint arXiv:2412.19437, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[5]
DeepSeek-R1: Incentivizing Reasoning Capability in LLMs via Reinforcement Learning
Daya Guo, Dejian Yang, Haowei Zhang, Junxiao Song, Ruoyu Zhang, Runxin Xu, Qihao Zhu, Shirong Ma, Peiyi Wang, Xiao Bi, et al. Deepseek-r1: Incentivizing reasoning capability in llms via reinforcement learning.arXiv preprint arXiv:2501.12948, 2025
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[6]
Andreas Antoniou and Wu-Sheng Lu.Practical optimization: algorithms and engineering applications. Springer, 2007
work page 2007
-
[7]
David G Luenberger, Yinyu Ye, et al.Linear and nonlinear programming, volume 2. Springer, 1984
work page 1984
-
[8]
Hongliang Lu, Zhonglin Xie, Yaoyu Wu, Can Ren, Yuxuan Chen, and Zaiwen Wen. Optmath: A scalable bidirectional data synthesis framework for optimization modeling.arXiv preprint arXiv:2502.11102, 2025
-
[9]
Chenyu Huang, Zhengyang Tang, Shixi Hu, Ruoqing Jiang, Xin Zheng, Dongdong Ge, Benyou Wang, and Zizhuo Wang. Orlm: A customizable framework in training large models for automated optimization modeling.Operations Research, 2025
work page 2025
-
[10]
Zhicheng Yang, Yinya Huang, Wei Shi, Liang Feng, Linqi Song, Yiwei Wang, Xiaodan Liang, and Jing Tang. Benchmarking llms for optimization modeling and enhancing reasoning via reverse socratic synthesis.arXiv e-prints, pages arXiv–2407, 2024
work page 2024
-
[11]
Xia Jiang, Yaoxin Wu, Minshuo Li, Zhiguang Cao, and Yingqian Zhang. Large language models as end-to-end combinatorial optimization solvers.arXiv preprint arXiv:2509.16865, 2025
-
[12]
Large language models still can’t plan (a benchmark for llms on planning and reasoning about change)
Karthik Valmeekam, Alberto Olmo, Sarath Sreedharan, and Subbarao Kambhampati. Large language models still can’t plan (a benchmark for llms on planning and reasoning about change). InNeurIPS 2022 Foundation Models for Decision Making Workshop, 2022
work page 2022
-
[13]
Gurobi Optimizer Reference Manual, 2024
Gurobi Optimization, LLC. Gurobi Optimizer Reference Manual, 2024
work page 2024
-
[14]
Cardinal optimizer (copt) user guide.arXiv preprint arXiv:2208.14314, 2022
Dongdong Ge, Qi Huangfu, Zizhuo Wang, Jian Wu, and Yinyu Ye. Cardinal optimizer (copt) user guide. arXiv preprint arXiv:2208.14314, 2022
-
[15]
Rindra Ramamonjison, Haley Li, Timothy Yu, Shiqi He, Vishnu Rengan, Amin Banitalebi-Dehkordi, Zirui Zhou, and Yong Zhang. Augmenting operations research with auto-formulation of optimization models from problem descriptions. InProceedings of the 2022 Conference on Empirical Methods in Natural Language Processing: Industry Track, pages 29–62, 2022
work page 2022
-
[16]
International Conference on Machine Learning (ICML) , video=
Ali AhmadiTeshnizi, Wenzhi Gao, and Madeleine Udell. Optimus: Scalable optimization modeling with (mi) lp solvers and large language models.arXiv preprint arXiv:2402.10172, 2024
-
[17]
InProceedings of the 41st International Conference on Machine Learning, pages 577–596
Yitian Chen, Jingfan Xia, Siyu Shao, Dongdong Ge, and Yinyu Ye. Solver-informed rl: Grounding large language models for authentic optimization modeling.arXiv preprint arXiv:2505.11792, 2025
-
[18]
Learning to reason with LLMs, September 2024
OpenAI. Learning to reason with LLMs, September 2024. Accessed: 2026-01-07
work page 2024
-
[19]
Jason Wei, Xuezhi Wang, Dale Schuurmans, Maarten Bosma, Fei Xia, Ed Chi, Quoc V Le, Denny Zhou, et al. Chain-of-thought prompting elicits reasoning in large language models.Advances in neural information processing systems, 35:24824–24837, 2022
work page 2022
-
[20]
An Yang, Anfeng Li, Baosong Yang, Beichen Zhang, Binyuan Hui, Bo Zheng, Bowen Yu, Chang Gao, Chengen Huang, Chenxu Lv, et al. Qwen3 technical report.arXiv preprint arXiv:2505.09388, 2025
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[21]
Towards optimizing with large language models.arXiv preprint arXiv:2310.05204, 2023
Pei-Fu Guo, Ying-Hsuan Chen, Yun-Da Tsai, and Shou-De Lin. Towards optimizing with large language models.arXiv preprint arXiv:2310.05204, 2023. 11
-
[22]
Nl4opt competition: Formulating optimization problems based on their natural language descriptions
Rindranirina Ramamonjison, Timothy Yu, Raymond Li, Haley Li, Giuseppe Carenini, Bissan Ghaddar, Shiqi He, Mahdi Mostajabdaveh, Amin Banitalebi-Dehkordi, Zirui Zhou, et al. Nl4opt competition: Formulating optimization problems based on their natural language descriptions. InNeurIPS 2022 competition track, pages 189–203. PMLR, 2023
work page 2022
-
[23]
Mamo: a mathematical modeling benchmark with solvers.arXiv e-prints, pages arXiv–2405, 2024
Xuhan Huang, Qingning Shen, Yan Hu, Anningzhe Gao, and Benyou Wang. Mamo: a mathematical modeling benchmark with solvers.arXiv e-prints, pages arXiv–2405, 2024
work page 2024
-
[24]
Zhicheng Yang, Yiwei Wang, Yinya Huang, Zhijiang Guo, Wei Shi, Xiongwei Han, Liang Feng, Linqi Song, Xiaodan Liang, and Jing Tang. Optibench meets resocratic: Measure and improve llms for optimization modeling.arXiv preprint arXiv:2407.09887, 2024
-
[25]
Yuki Imajuku, Kohki Horie, Yoichi Iwata, Kensho Aoki, Naohiro Takahashi, and Takuya Akiba. Ale-bench: A benchmark for long-horizon objective-driven algorithm engineering.arXiv preprint arXiv:2506.09050, 2025
-
[26]
Xiaozhe Li, Xinyu Fang, Shengyuan Ding, Linyang Li, Haodong Duan, Qingwen Liu, and Kai Chen. Np-engine: Empowering optimization reasoning in large language models with verifiable synthetic np problems.arXiv preprint arXiv:2510.16476, 2025
-
[27]
Duc M Nguyen and Sungahn Ko. Technical report for icml 2024 automated math reasoning challenge: Solving optimization problems with open source large language model. InAI for Math Workshop@ ICML 2024, 2024
work page 2024
-
[28]
Large language models as optimizers
Chengrun Yang, Xuezhi Wang, Yifeng Lu, Hanxiao Liu, Quoc V Le, Denny Zhou, and Xinyun Chen. Large language models as optimizers. InThe Twelfth International Conference on Learning Representations, 2023
work page 2023
-
[29]
Jianheng Tang, Qifan Zhang, Yuhan Li, Nuo Chen, and Jia Li. Grapharena: Evaluating and exploring large language models on graph computation.arXiv preprint arXiv:2407.00379, 2024
-
[30]
Acpbench: Reasoning about action, change, and planning
Harsha Kokel, Michael Katz, Kavitha Srinivas, and Shirin Sohrabi. Acpbench: Reasoning about action, change, and planning. InProceedings of the AAAI Conference on Artificial Intelligence, volume 39, pages 26559–26568, 2025
work page 2025
-
[31]
Zhao Song, Song Yue, and Jiahao Zhang. Thinking isn’t an illusion: Overcoming the limitations of reasoning models via tool augmentations.arXiv preprint arXiv:2507.17699, 2025
-
[32]
Karthik Valmeekam, Kaya Stechly, and Subbarao Kambhampati. Llms still can’t plan; can lrms? a preliminary evaluation of openai’s o1 on planbench.arXiv preprint arXiv:2409.13373, 2024
-
[33]
Karthik Valmeekam, Kaya Stechly, Atharva Gundawar, and Subbarao Kambhampati. A systematic evaluation of the planning and scheduling abilities of the reasoning model o1.Transactions on Machine Learning Research, 2025
work page 2025
-
[34]
Parshin Shojaee, Iman Mirzadeh, Keivan Alizadeh, Maxwell Horton, Samy Bengio, and Mehrdad Farajtabar. The illusion of thinking: Understanding the strengths and limitations of reasoning models via the lens of problem complexity.arXiv preprint arXiv:2506.06941, 2025
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[35]
GSM-Symbolic: Understanding the Limitations of Mathematical Reasoning in Large Language Models
Iman Mirzadeh, Keivan Alizadeh, Hooman Shahrokhi, Oncel Tuzel, Samy Bengio, and Mehrdad Fara- jtabar. Gsm-symbolic: Understanding the limitations of mathematical reasoning in large language models.arXiv preprint arXiv:2410.05229, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[36]
Pengfei Hong, Deepanway Ghosal, Navonil Majumder, Somak Aditya, Rada Mihalcea, and Soujanya Poria. Stuck in the quicksand of numeracy, far from agi summit: Evaluating llms’ mathematical competency through ontology-guided perturbations.CoRR, 2024
work page 2024
-
[37]
Math-perturb: Benchmarking llms’ math reasoning abilities against hard perturbations
Kaixuan Huang, Jiacheng Guo, Zihao Li, Xiang Ji, Jiawei Ge, Wenzhe Li, Yingqing Guo, Tianle Cai, Hui Yuan, Runzhe Wang, et al. Math-perturb: Benchmarking llms’ math reasoning abilities against hard perturbations.arXiv preprint arXiv:2502.06453, 2025
-
[38]
Judging llm-as-a-judge with mt-bench and chatbot arena
Lianmin Zheng, Wei-Lin Chiang, Ying Sheng, Siyuan Zhuang, Zhanghao Wu, Yonghao Zhuang, Zi Lin, Zhuohan Li, Dacheng Li, Eric Xing, et al. Judging llm-as-a-judge with mt-bench and chatbot arena. Advances in neural information processing systems, 36:46595–46623, 2023
work page 2023
-
[39]
DeepSeek-V3.2: Pushing the Frontier of Open Large Language Models
Aixin Liu, Aoxue Mei, Bangcai Lin, Bing Xue, Bingxuan Wang, Bingzheng Xu, Bochao Wu, Bowei Zhang, Chaofan Lin, Chen Dong, et al. Deepseek-v3. 2: Pushing the frontier of open large language models.arXiv preprint arXiv:2512.02556, 2025. 12
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[40]
Gheorghe Comanici, Eric Bieber, Mike Schaekermann, Ice Pasupat, Noveen Sachdeva, Inderjit Dhillon, Marcel Blistein, Ori Ram, Dan Zhang, Evan Rosen, et al. Gemini 2.5: Pushing the frontier with advanced reasoning, multimodality, long context, and next generation agentic capabilities.arXiv preprint arXiv:2507.06261, 2025
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[41]
Interpolated estimation of markov source parameters from sparse data
Frederick Jelinek. Interpolated estimation of markov source parameters from sparse data. InProc. Workshop on Pattern Recognition in Practice, 1980, 1980
work page 1980
-
[42]
HybridFlow: A Flexible and Efficient RLHF Framework
Guangming Sheng, Chi Zhang, Zilingfeng Ye, Xibin Wu, Wang Zhang, Ru Zhang, Yanghua Peng, Haibin Lin, and Chuan Wu. Hybridflow: A flexible and efficient rlhf framework.arXiv preprint arXiv:2409.19256, 2024
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[43]
The Curious Case of Neural Text Degeneration
Ari Holtzman, Jan Buys, Li Du, Maxwell Forbes, and Yejin Choi. The curious case of neural text degeneration.arXiv preprint arXiv:1904.09751, 2019. 13 A Technical Background A.1 Auto-formulation of Optimization Problems In this work, auto-formulation denotes the task of using an LLM-based agent to transform a human-readable problem description into this fo...
work page internal anchor Pith review Pith/arXiv arXiv 1904
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