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Auteurs principaux: Liu, Yang, Zhou, Chuan, Chen, Yancheng, Zhang, Shuai, Lin, Xixun, Wang, Xiaoqing
Format: Preprint
Publié: 2026
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Accès en ligne:https://arxiv.org/abs/2602.01090
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author Liu, Yang
Zhou, Chuan
Chen, Yancheng
Zhang, Shuai
Lin, Xixun
Wang, Xiaoqing
author_facet Liu, Yang
Zhou, Chuan
Chen, Yancheng
Zhang, Shuai
Lin, Xixun
Wang, Xiaoqing
contents Large language models (LLMs) have emerged as promising general-purpose solvers for combinatorial optimization (CO), yet they fundamentally lack mechanisms to guarantee solution feasibility which is critical for real-world deployment. In this work, we introduce FALCON, a framework that ensures 100\% feasibility through three key innovations: (i) \emph{grammar-constrained decoding} enforces syntactic validity, (ii) a \emph{feasibility repair layer} corrects semantic constraint violations, and (iii) \emph{adaptive Best-of-$N$ sampling} allocates inference compute efficiently. To train the underlying LLM, we introduce the Best-anchored Objective-guided Preference Optimization (BOPO) in LLM training, which weights preference pairs by their objective gap, providing dense supervision without human labels. Theoretically, we prove convergence for BOPO and provide bounds on repair-induced quality loss. Empirically, across seven NP-hard CO problems, FALCON achieves perfect feasibility while matching or exceeding the solution quality of state-of-the-art neural and LLM-based solvers.
format Preprint
id arxiv_https___arxiv_org_abs_2602_01090
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Hard Constraints Meet Soft Generation: Guaranteed Feasibility for LLM-based Combinatorial Optimization
Liu, Yang
Zhou, Chuan
Chen, Yancheng
Zhang, Shuai
Lin, Xixun
Wang, Xiaoqing
Artificial Intelligence
Large language models (LLMs) have emerged as promising general-purpose solvers for combinatorial optimization (CO), yet they fundamentally lack mechanisms to guarantee solution feasibility which is critical for real-world deployment. In this work, we introduce FALCON, a framework that ensures 100\% feasibility through three key innovations: (i) \emph{grammar-constrained decoding} enforces syntactic validity, (ii) a \emph{feasibility repair layer} corrects semantic constraint violations, and (iii) \emph{adaptive Best-of-$N$ sampling} allocates inference compute efficiently. To train the underlying LLM, we introduce the Best-anchored Objective-guided Preference Optimization (BOPO) in LLM training, which weights preference pairs by their objective gap, providing dense supervision without human labels. Theoretically, we prove convergence for BOPO and provide bounds on repair-induced quality loss. Empirically, across seven NP-hard CO problems, FALCON achieves perfect feasibility while matching or exceeding the solution quality of state-of-the-art neural and LLM-based solvers.
title Hard Constraints Meet Soft Generation: Guaranteed Feasibility for LLM-based Combinatorial Optimization
topic Artificial Intelligence
url https://arxiv.org/abs/2602.01090