Size versus truthfulness in the House Allocation problem

Krysta, P., Manlove, D. , Rastegari, B. and Zhang, J. (2019) Size versus truthfulness in the House Allocation problem. Algorithmica, 81(9), pp. 3422-3463. (doi: 10.1007/s00453-019-00584-7)

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We study the House Allocation problem (also known as the Assignment problem), i.e., the problem of allocating a set of objects among a set of agents, where each agent has ordinal preferences (possibly involving ties) over a subset of the objects. We focus on truthful mechanisms without monetary transfers for finding large Pareto optimal matchings. It is straightforward to show that no deterministic truthful mechanism can approximate a maximum cardinality Pareto optimal matching with ratio better than 2. We thus consider randomised mechanisms. We give a natural and explicit extension of the classical Random Serial Dictatorship Mechanism (RSDM) specifically for the House Allocation problem where preference lists can include ties. We thus obtain a universally truthful randomised mechanism for finding a Pareto optimal matching and show that it achieves an approximation ratio of ee−1. The same bound holds even when agents have priorities (weights) and our goal is to find a maximum weight (as opposed to maximum cardinality) Pareto optimal matching. On the other hand we give a lower bound of 1813 on the approximation ratio of any universally truthful Pareto optimal mechanism in settings with strict preferences. By using a characterisation result of Bade, we show that any randomised mechanism that is a symmetrisation of a truthful, non-bossy and Pareto optimal mechanism has an improved lower bound of ee−1. Since our new mechanism is a symmetrisation of RSDM for strict preferences, it follows that this lower bound is tight. We moreover interpret our problem in terms of the classical secretary problem and prove that our mechanism provides the best randomised strategy of the administrator who interviews the applicants.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Rastegari, Dr Baharak and Manlove, Professor David
Authors: Krysta, P., Manlove, D., Rastegari, B., and Zhang, J.
College/School:College of Science and Engineering > School of Computing Science
Journal Name:Algorithmica
ISSN (Online):1432-0541
Published Online:18 May 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Algorithmica 81(9):3422-3463
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
607071Efficient Algorithms for Mechanism Design Without Monetary Transfer.David ManloveEngineering and Physical Sciences Research Council (EPSRC)EP/K010042/1COM - COMPUTING SCIENCE
3008080IP-MATCH: Integer Programming for Large and Complex Matching ProblemsDavid ManloveEngineering and Physical Sciences Research Council (EPSRC)EP/P028306/1Computing Science