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Towards Efficiently Implementing Dodgson’s Formally Intractable Voting Rule

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Abstract

Conflict of interest is the permanent companion of any population of agents (computational or biological). For that reason, the ability to compromise is of paramount importance, making voting a key element of societal mechanisms. A voting procedure often discussed in the literature and, due to its intuitiveness, also conceptually quite appealing is Charles Dodgson’s scoring rule, basically using the respective closeness to being a Condorcet winner for evaluating competing alternatives. In this paper, we offer insights into the practical limits of algorithms computing the exact Dodgson scores from a number of votes. While the problem itself is theoretically intractable, this work proposes and analyses five different solutions which try distinct approaches to practically solve the issue in an effective manner. Additionally, three of the discussed procedures can be run in parallel which has the potential of drastically improving computational performance on the problem.

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Notes

  1. The source code of the project software is available from https://sourceforge.net/projects/dodgsonscoring/.

  2. In a Borda count voters rank alternatives in order of preference. The outcome is determined by assigning each alternative, for each ballot, a number of points corresponding to the number of candidates ranked lower. The alternative with the highest number of points, summed up over all cast votes, is the winner.

  3. Similar to [5], even values for n were omitted as the performance of multiprocessing algorithms is influenced by the probability of there being a Condorcet winner. Even numbers of agents make this significantly less likely due to ties, resulting in the graph spiking after every other value.

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Correspondence to Tarek R. Besold.

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Recknagel, A., Besold, T.R. Towards Efficiently Implementing Dodgson’s Formally Intractable Voting Rule. Künstl Intell 31, 161–167 (2017). https://doi.org/10.1007/s13218-016-0454-8

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  • DOI: https://doi.org/10.1007/s13218-016-0454-8

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