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arXiv 2202.01660cs.GTcs.AI
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条件赞成投票中胜者确定与策略控制的复杂性

On the Complexity of Winner Determination and Strategic Control in Conditional Approval Voting

Athens University of Economics and Business(雅典经济与商业大学);Archimedes, Athena Research Center(阿基米德、雅典研究中心);Input Output Global (IOG)(输入输出全球(IOG));University of Warsaw(华沙大学)

Evangelos Markakis, Georgios Papasotiropoulos

AI总结:

本文研究条件赞成投票 CMS 的胜者确定复杂性,证明有界树宽是精确多项式可解的充要条件,给出受限二元议题下的首批乘法近似算法,并表明其对多数控制操作具有计算抗性。

摘要:

我们关注由 Barrot 和 Lang(2016)提出的经典 Minisum 赞成投票规则的一种推广,称为 Conditional Minisum(CMS),用于存在偏好依赖的多议题选举。在该规则下,选民可以声明不同议题之间的依赖关系,但为这种更高表达能力所付出的代价是,该规则在计算上变得困难。受此启发,我们首先关注寻找允许 CMS 使用高效算法的特殊情形。我们在这一方向上的主要结果是:在常见复杂性假设下,确定了(由所提交选票产生的适当图的)有界树宽这一条件,将其作为存在精确多项式算法的充要条件。随后,我们转向近似算法的设计。对于二元议题这一仍然困难的情形,我们识别了对选民选票的自然限制,并在这些限制下给出了该问题的首批乘法近似算法。这些限制包括:一个议题对其他议题的依赖数量上界,以及每位选民在每个议题上可赞成的备选方案数量上界。最后,我们还研究了通过增加或删除选民或备选方案来对条件赞成选举进行策略控制的相关问题的复杂性,并表明在这些问题的大多数变体中,CMS 在计算上对控制具有抗性。总体而言,我们得出结论:当议题之间的依赖数量有限时,CMS 可被视为一种在表达能力与计算效率之间实现令人满意的折中的解决方案,同时表现出足够的控制抗性。

英文摘要:

We focus on a generalization of the classic Minisum approval voting rule, introduced by Barrot and Lang (2016), and referred to as Conditional Minisum (CMS), for multi-issue elections with preferential dependencies. Under this rule, voters are allowed to declare dependencies between different issues, but the price we have to pay for this higher level of expressiveness is that we end up with a computationally hard rule. Motivated by this, we first focus on finding special cases that admit efficient algorithms for CMS. Our main result in this direction is that we identify the condition of bounded treewidth (of an appropriate graph, emerging from the provided ballots) as the necessary and sufficient condition for exact polynomial algorithms, under common complexity assumptions. We then move to the design of approximation algorithms. For the (still hard) case of binary issues, we identify natural restrictions on the voters' ballots, under which we provide the first multiplicative approximation algorithms for the problem. The restrictions involve upper bounds on the number of dependencies an issue can have on the others and on the number of alternatives per issue that a voter can approve. Finally, we also investigate the complexity of problems related to the strategic control of conditional approval elections by adding or deleting either voters or alternatives and we show that in most variants of these problems, CMS is computationally resistant against control. Overall, we conclude that CMS can be viewed as a solution that achieves a satisfactory tradeoff between expressiveness and computational efficiency, when we have a limited number of dependencies among issues, while at the same time exhibiting sufficient resistance to control.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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