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Main Authors: Fitzsimmons, Zack, Hassan, Zohair Raza, Hemaspaandra, Edith
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2501.15006
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author Fitzsimmons, Zack
Hassan, Zohair Raza
Hemaspaandra, Edith
author_facet Fitzsimmons, Zack
Hassan, Zohair Raza
Hemaspaandra, Edith
contents Approval-Based Committee (ABC) rules are an important tool for choosing a fair set of candidates when given the preferences of a collection of voters. Though finding a winning committee for many ABC rules is NP-hard, natural variations for these rules with polynomial-time algorithms exist. The recently introduced Method of Equal Shares, an important ABC rule with desirable properties, is also computable in polynomial time. However, when working with very large elections, polynomial time is not enough and parallelization may be necessary. We show that computing a winning committee using these polynomial-time ABC rules (including the Method of Equal Shares) is P-hard, thus showing they cannot be parallelized. In contrast, we show that finding a winning committee can be parallelized when the votes are single-peaked or single-crossing for the important ABC rule Chamberlin-Courant.
format Preprint
id arxiv_https___arxiv_org_abs_2501_15006
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Parallelizability of Approval-Based Committee Rules
Fitzsimmons, Zack
Hassan, Zohair Raza
Hemaspaandra, Edith
Computer Science and Game Theory
Approval-Based Committee (ABC) rules are an important tool for choosing a fair set of candidates when given the preferences of a collection of voters. Though finding a winning committee for many ABC rules is NP-hard, natural variations for these rules with polynomial-time algorithms exist. The recently introduced Method of Equal Shares, an important ABC rule with desirable properties, is also computable in polynomial time. However, when working with very large elections, polynomial time is not enough and parallelization may be necessary. We show that computing a winning committee using these polynomial-time ABC rules (including the Method of Equal Shares) is P-hard, thus showing they cannot be parallelized. In contrast, we show that finding a winning committee can be parallelized when the votes are single-peaked or single-crossing for the important ABC rule Chamberlin-Courant.
title On the Parallelizability of Approval-Based Committee Rules
topic Computer Science and Game Theory
url https://arxiv.org/abs/2501.15006