Unique lifting of integer variables in minimal inequalities
Abstract
This paper contributes to the theory of cutting planes for mixed integer linear programs (MILPs). Minimal valid inequalities are well understood for a relaxation of an MILP in tableau form where all the nonbasic variables are continuous; they are derived using the gauge function of maximal lattice-free convex sets. In this paper we study lifting functions for the nonbasic integer variables starting from such minimal valid inequalities. We characterize precisely when the lifted coefficient is equal to the coefficient of the corresponding continuous variable in every minimal lifting. The answer is a nonconvex region that can be obtained as a finite union of convex polyhedra. We then establish a necessary and sufficient condition for the uniqueness of the lifting function.
Cite
@article{arxiv.1701.06628,
title = {Unique lifting of integer variables in minimal inequalities},
author = {Amitabh Basu and Manoel Campelo and Michele Conforti and Gerard Cornuejols and Giacomo Zambelli},
journal= {arXiv preprint arXiv:1701.06628},
year = {2017}
}
Comments
A subset of these results appeared in Proceedings of IPCO 2010, LNCS 6080, 2010, pp. 85--95