A constraint program for solving the job-shop problem

Abstract

In this paper, a method within the framework of propagation of interval constraints and based on the branch-and-bound optimization scheme for solving the job-shop scheduling problem will be presented. The goal is to provide a constraint program which is clean, flexible and robust. The design of the constraint program is based on an idea of sorting the release and due dates of tasks, which is a successful application of a previous but not yet published work on a distinct integers constraint. Based on the sorting constraint, by assembling redundant constraints and applying an efficient search strategy, the current program for the job-shop problem can solve the ten 10 x 10 instances in the paper of Applegate and Cook (1991) in satisfactory computational time. Moreover, good results have been achieved on some harder instances.