Discrete Particle Swarm Optimization for Job Shop Scheduling Problem with Parallel Machine

Since the production scheduling is covered the wide range of manufacturing and services systems, the types of related issues are highly diverse. In advanced manufacturing environments, because the production flexibility property is taking into account as a competitive advantage, in this paper a special kind of flexibility in the job shop scheduling problem is defined in which, for jobs processing, each workstation have multiple parallel machines. Processing speed of each machine can also be different. The objective of this problem is to minimize the maximum completion time (makespan). Due to NPhardness of problem, we proposed a metaheuristic algorithm. In the proposed approach, due to the structure of the problem and its discrete enviorment, we modified a particle swarm optimization as a new discrete algorithm. Finally to evaluate the performance of the algorithm, the proposed algorithm has been compared with several heuristics existing in the literature.