1. Institut für Informatik, University of Cologne, D-50969, K?ln, Germany 2. Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ont., Canada
Abstract:
The permutahedron of a poset is the convex hull of all incidence vectors of linear extensions. For the case ofN-sparse posets in which any five elements induce at most oneN we give a characterization of the permutahedron in terms of linear inequalities. This yields an LP-solution for minimizing the weighted mean completion time for jobs with unit processing times andN-sparse precedence constraints. We close with an extension of our approach to arbitrary processing times.