Authors: Ricardo Fukasawa Marcos Goycoolea
Publish Date: 2009/06/06
Volume: 128, Issue: 1-2, Pages: 19-41
Abstract
During the last decades much research has been conducted on deriving classes of valid inequalities for mixed integer knapsack sets which we call knapsack cuts Bixby et al The sharpest cut the impact of Manfred Padberg and his work MPS/SIAM Series on Optimization pp 309–326 2004 empirically observe that within the context of branchandcut algorithms to solve mixed integer programming problems the most important inequalities are knapsack cuts derived by the mixed integer rounding MIR procedure In this work we analyze this empirical observation by developing an algorithm to separate over the convex hull of a mixed integer knapsack set The main feature of this algorithm is a specialized subroutine for optimizing over a mixed integer knapsack set which exploits dominance relationships The exact separation of knapsack cuts allows us to establish natural benchmarks by which to evaluate specific classes of them Using these benchmarks on MIPLIB 30 and MIPLIB 2003 instances we analyze the performance of MIR inequalities Our computations which are performed in exact arithmetic are surprising In the vast majority of the instances in which knapsack cuts yield bound improvements MIR cuts alone achieve over 87 of the observed gain
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