Solution of job-shop scheduling problems by an idle time shortening genetic algorithm

In this paper, we propose a new idle time shortening method for job-shop scheduling problems (JSPs). We insert our method into a genetic algorithm (GA). The purpose of JSP is to find a schedule with the minimum makespan. We consider that it is effective to reduce idle time of a machine in order to improve the makespan. The left shift is well-known among existing algorithms for shortening idle time. The left shift cannot arrange the work to idle time. For that reason, some idle times are not shortened by left shift. We propose two kinds of algorithms which shorten such idle time. Next, we combine these algorithms and the reversal of a schedule. We apply GA with its algorithm to benchmark problems and demonstrate its effectiveness. (C) 2007 Wiley Periodicals, Inc.