What is Sequence Dependent Setup Times

This chapter deals with a hybrid flow shop scheduling problem involving sequence dependent setup times, commonly known as the SDST hybrid flow shop, and each stage (work centre) consists of parallel identical machines. In this problem, each job has a different release date and consists of ordered operations that must be processed on machines from different centers in the same order. In addition, the processing times of operations on some machine centers may vary between a minimum and a maximum value depending on the use of a continuously divisible resource. We consider a non-regular optimization criterion based on due dates which are not a priori given or fixed but can be assigned by a decision-maker. A due date assignment cost is also included into the objective function. Finally, the results obtained through the use of GRASP (Greedy Randomized Adaptive Search Procedure) are compared with those computed by SA (Simulated Annealing).