Flowshop scheduling problem with parallel semi-lines and final synchronization operation.

This paper deals with a particular variant of the flowshop scheduling problem motivated by a real case configuration issued from an electro-electronic material industry. The shop floor environment is composed of two parallel semi-lines and a final synchronization operation. The jobs must follow the same technological order through the machines on each parallel semi-line. However, the operations on each semi-line are independent. The final synchronization operation, operated by a dedicated machine, can only start when the job is finished on both semi-lines. The objective is to determine a schedule that minimizes the makespan for a given set of jobs. Since this problem class is NP-hard in the strong sense, constructive heuristic procedures and metaheuristics methods are introduced to achieve optimal or near-optimal solutions. The performances of the proposed GRASP and the Simulated Annealing algorithms are evaluated and compared with the adaptation of two well-known heuristics. Computational experiments show that the proposed metaheuristics provide very good results in low computational times