Approximate Multi-matroid Intersection via Iterative Refinement

André Linhares, Neil Olver, Chaitanya Swamy, Rico Zenklusen*

*Corresponding author for this work

Research output: Chapter in Book / Report / Conference proceedingConference contributionAcademicpeer-review

Abstract

We introduce a new iterative rounding technique to round a point in a matroid polytope subject to further matroid constraints. This technique returns an independent set in one matroid with limited violations of the other ones. On top of the classical steps of iterative relaxation approaches, we iteratively refine/split involved matroid constraints to obtain a more restrictive constraint system, that is amenable to iterative relaxation techniques. Hence, throughout the iterations, we both tighten constraints and later relax them by dropping constraints under certain conditions. Due to the refinement step, we can deal with considerably more general constraint classes than existing iterative relaxation/rounding methods, which typically round on one matroid polytope with additional simple cardinality constraints that do not overlap too much. We show how our rounding method, combined with an application of a matroid intersection algorithm, yields the first 2-approximation for finding a maximum-weight common independent set in 3 matroids. Moreover, our 2-approximation is LP-based, and settles the integrality gap for the natural relaxation of the problem. Prior to our work, no upper bound better than 3 was known for the integrality gap, which followed from the greedy algorithm. We also discuss various other applications of our techniques, including an extension that allows us to handle a mixture of matroid and knapsack constraints.

Original languageEnglish
Title of host publicationInteger Programming and Combinatorial Optimization
Subtitle of host publication20th International Conference, IPCO 2019, Ann Arbor, MI, USA, May 22–24, 2019, Proceedings
EditorsViswanath Nagarajan, Andrea Lodi
PublisherSpringer Verlag
Pages299-312
Number of pages14
ISBN (Electronic)9783030179533
ISBN (Print)9783030179526
DOIs
Publication statusPublished - 2019
Event20th International Conference on Integer Programming and Combinatorial Optimization, IPCO 2019 - Ann Arbor, United States
Duration: 22 May 201924 May 2019

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume11480 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference20th International Conference on Integer Programming and Combinatorial Optimization, IPCO 2019
CountryUnited States
CityAnn Arbor
Period22/05/1924/05/19

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