Abstract
Sherali and Adams (SIAM J Discrete Math 3:411–430, 1990) and Lovász and Schrijver (SIAM J Optim 1:166–190, 1991) developed systematic procedures to construct the hierarchies of relaxations known as lift-and-project methods. They have been proven to be a strong tool for developing approximation algorithms, matching the best relaxations known for problems like Max-Cut and Sparsest-Cut. In this work we provide lower bounds for these hierarchies when applied over the configuration LP for the problem of scheduling identical machines to minimize the makespan. First we show that the configuration LP has an integrality gap of at least 1024/1023 by providing a family of instances with 15 different job sizes. Then we show that for any integer n there is an instance with n jobs in this family such that after Ω(n) rounds of the Sherali–Adams (SA) or the Lovász–Schrijver (LS+) hierarchy the integrality gap remains at least 1024/1023.
Original language | English |
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Pages (from-to) | 231-248 |
Number of pages | 18 |
Journal | Math. Program. |
Volume | 172 |
Issue number | 1-2 |
Early online date | 10 May 2017 |
DOIs | |
Publication status | Published - Nov 2018 |
Funding
Supported by the Swiss National Science Foundation project 200020-144491/1 “Approximation Algorithms for Machine Scheduling Through Theory and Experiments,” by Sciex Project 12.311, by DFG Grant MO 2889/1-1, and by CONICYT-PCHA/Doctorado Nacional/2014-21140930. Supported by the Swiss National Science Foundation project 200020-144491/1 ?Approximation Algorithms for Machine Scheduling Through Theory and Experiments,? by Sciex Project 12.311, by DFG Grant MO 2889/1-1, and by CONICYT-PCHA/Doctorado Nacional/2014-21140930.
Funders | Funder number |
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CONICYT-PCHA/Doctorado | Nacional/2014-21140930 |
California Department of Fish and Game | |
Deutsche Forschungsgemeinschaft | MO 2889/1-1 |
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung | 12.311, 200020-144491/1 |