菜单

关于 🐙 GitHub
arXiv 提交日期: 2026-04-21
📄 Abstract - Is Four Enough? Automated Reasoning Approaches and Dual Bounds for Condorcet Dimensions of Elections

In an election where $n$ voters rank $m$ candidates, a Condorcet winning set is a committee of $k$ candidates such that for any outside candidate, a majority of voters prefer some committee member. Condorcet's paradox shows that some elections admit no Condorcet winning sets with a single candidate (i.e., $k=1$), and the same can be shown for $k=2$. On the other hand, recent work proves that a set of size $k=5$ exists for every election. This leaves an important theoretical gap between the best known lower bound $(k\geq 3)$ and upper bound $(k \leq 5)$ for the number of candidates needed to guarantee existence. We aim to close the gap between the existence guarantees and impossibility results for Condorcet winning sets. We explore an automated reasoning approach to tighten these bounds. We design a mixed-integer linear program (MILP) to search for elections that would serve as counter-examples to conjectured bounds. We employ a number of optimizations, such as symmetry breaking, subsampling, and constraint generation, to enhance the search and model effectively infinite electorates. Furthermore, we analyze the dual of the linear programming relaxation as a path towards obtaining a new upper bound. Despite extensive search on moderate-sized elections, we fail to find any election requiring a committee larger than size 3. Motivated by our experimental results in this direction, we simplify the dual linear program and formulate a conjecture which, if true, implies that a winning set of size 4 always exists. Our automated reasoning results provide strong empirical evidence that the Condorcet dimension of any election may be smaller than currently known upper bounds, at least for small instances. We offer a general-purpose framework for searching elections in ranked voting and a new, concrete analytical path via duality toward proving that smaller committees suffice.

顶级标签: machine learning theory
详细标签: automated reasoning condorcet winning set mixed-integer linear program election theory duality 或 搜索:

四人是否足够?——选举中Condorcet维数的自动推理方法与对偶界 / Is Four Enough? Automated Reasoning Approaches and Dual Bounds for Condorcet Dimensions of Elections


1️⃣ 一句话总结

本文通过混合整数线性规划和对偶分析,系统性地探索了选举中保证存在Condorcet获胜委员会所需的最小规模,实验结果表明多数选举仅需3位成员即可,并提出了一个支持“4人足够”的猜想,从而缩小了理论上下界之间的差距。

源自 arXiv: 2604.19851