Preferences single-peaked on nice trees

Preference profiles that are single-peaked on trees enjoy desirable properties: they admit a Condorcet winner (Demange 1982), and there are hard voting problems that become tractable on this domain (Yu et al., 2013). Trick (1989) proposed a polynomial-time algorithm that finds some tree with respect...

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Main Authors: Peters, D, Elkind, E
Formato: Conference item
Idioma:English
Publicado em: AAAI Press 2016
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author Peters, D
Elkind, E
author_facet Peters, D
Elkind, E
author_sort Peters, D
collection OXFORD
description Preference profiles that are single-peaked on trees enjoy desirable properties: they admit a Condorcet winner (Demange 1982), and there are hard voting problems that become tractable on this domain (Yu et al., 2013). Trick (1989) proposed a polynomial-time algorithm that finds some tree with respect to which a given preference profile is single-peaked. However, some voting problems are only known to be easy for profiles that are single-peaked on "nice" trees, and Trick's algorithm provides no guarantees on the properties of the tree that it outputs. To overcome this issue, we build on the work of Trick and Yu et al. to develop a structural approach that enables us to compactly represent all trees with respect to which a given profile is single-peaked. We show how to use this representation to efficiently find the "best" tree for a given profile, according to a number of criteria; for other criteria, we obtain NP-hardness results. In particular, we show that it is NP-hard to decide whether an input profile is single-peaked with respect to a given tree. To demonstrate the applicability of our framework, we use it to identify a new class of profiles that admit an efficient algorithm for a popular variant of the Chamberlin-Courant rule.
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spelling oxford-uuid:80a7457e-5014-44ad-a51a-17a08fa6e3e82022-03-26T21:24:45ZPreferences single-peaked on nice treesConference itemhttp://purl.org/coar/resource_type/c_5794uuid:80a7457e-5014-44ad-a51a-17a08fa6e3e8EnglishSymplectic ElementsAAAI Press2016Peters, DElkind, EPreference profiles that are single-peaked on trees enjoy desirable properties: they admit a Condorcet winner (Demange 1982), and there are hard voting problems that become tractable on this domain (Yu et al., 2013). Trick (1989) proposed a polynomial-time algorithm that finds some tree with respect to which a given preference profile is single-peaked. However, some voting problems are only known to be easy for profiles that are single-peaked on "nice" trees, and Trick's algorithm provides no guarantees on the properties of the tree that it outputs. To overcome this issue, we build on the work of Trick and Yu et al. to develop a structural approach that enables us to compactly represent all trees with respect to which a given profile is single-peaked. We show how to use this representation to efficiently find the "best" tree for a given profile, according to a number of criteria; for other criteria, we obtain NP-hardness results. In particular, we show that it is NP-hard to decide whether an input profile is single-peaked with respect to a given tree. To demonstrate the applicability of our framework, we use it to identify a new class of profiles that admit an efficient algorithm for a popular variant of the Chamberlin-Courant rule.
spellingShingle Peters, D
Elkind, E
Preferences single-peaked on nice trees
title Preferences single-peaked on nice trees
title_full Preferences single-peaked on nice trees
title_fullStr Preferences single-peaked on nice trees
title_full_unstemmed Preferences single-peaked on nice trees
title_short Preferences single-peaked on nice trees
title_sort preferences single peaked on nice trees
work_keys_str_mv AT petersd preferencessinglepeakedonnicetrees
AT elkinde preferencessinglepeakedonnicetrees