A Hybrid Harmony Search Algorithm for the Job Shop Scheduling Problems

Machine scheduling is assigning a set of operations of jobs on machines during a time period, taking into account the time, capability, and capacity constraints. In machine scheduling and management science, job shop scheduling is considered as an important problem due to many real-world applications. The job shop scheduling problems are numerically intractable that cannot be solved in polynomial time, unless P = NP, and they are classified as NP-hard. Harmony search algorithm has been successfully implemented in many optimization problems, particularly in scheduling problems, and hybridization is an effective approach for improving the solution quality of the algorithm. This paper proposes an effective hybrid harmony search algorithm for solving the job shop scheduling problems with the objective of minimizing makespan. A set of well-studied benchmarked problems is used to prove the effectiveness and efficiency of the proposed algorithm. The results indicate that the proposed hybrid harmony search algorithm improves the efficiency.