authors 
Balas, Egon 
year 
1984 
title 
On the Facial Structure of Scheduling Polyhedra 
source 
49 p., 6 p. of appendix : ill. Pittsburgh, PA: Design Research Center, Carnegie Mellon Univ., December, 1984. includes bibliography 
summary 
A wellknown job shop scheduling problem can be formulated as follows. Given a graph G with node set N and with directed and undirected arcs, find an orientation of the undirected arcs that minimizes the length of a longest path in G. The author treats the problem as a disjunctive program, without recourse to integer variables, and give a partial characterization of the scheduling polyhedron P(N), i.e., the convex hull of feasible schedules. In particular, he derives all the facets inducing inequalities for the scheduling polyhedron P(K) defined on some clique with node set K, and gives a sufficient condition for such inequalities to also induce facets of P(N). One of our results is that any inequality that induces a facet of P(H) for some HCK, also induces a facet of P(K). Another one is a recursive formula for deriving a facet inducing inequality with p positive coefficients from one with p1 positive coefficients. The author also addresses the constraint identification problem, and gives a procedure for finding an inequality that cuts off a given solution to a subset of the constraints 
keywords 
polyhedra, graphs, optimization, convex hull 
series 
CADline 
references 
Contenttype: text/plain

last changed 
1999/02/12 14:07 
