An Evaluation of Sequencing Heuristics for Flexible Flowshop Scheduling Problems with Unrelated Parallel Machines and Dual Criteria

This paper deals with the heuristic solution of flexible flowshop scheduling problems with unrelated parallel machines. A setup time is necessary before starting the processing of a job, where the setup time depends on the previous job. No preemption of jobs is allowed. As objective function, this paper considers the minimization of the positively weighted convex sum of makespan and the number of tardy jobs. This paper develops some well-known constructive heuristics for the pure flowshop scheduling problems such as the algorithms given by Palmer (1965), Campbell, Dudek, and Smith (1970), Gupta (1971), and Dannenbring (1977) as well as the insertion heuristic by Nawaz, Enscore and Ham (1983) to the flexible flowshop environment. By using one of these heuristics, the first stage sequence is generated. This sequence will then be used, in conjunction with either FIFO or permutation rules, to construct a schedule for the overall problem. The final solution is then the best schedule obtained by one of the two rules. Furthermore, some iterative heuristics such as a genetic algorithm and a simulated annealing approach are proposed to increase the quality of the constructive solution. Detailed computational results are presented to evaluate the efficiency of the heuristic algorithms. Detailed computational results with the algorithms are presented. © 2005 Elseviser B. V. All rights reserved.