Hybrid metaheuristic algorithms for the tardiness blocking flow shop problem

This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorithm, which are both combined with a variable neighbourhood search (VNS), for dealing with the flow shop problem with blocking, in order to minimize the total tardiness of jobs. The structure of both algorithms is very similar, but they differ in the way that the search is diversified in the space of solutions. In the ILS algorithm, the diversification is performed by a perturbation mechanism that takes into account some characteristics of the problem; whereas the perturbation in the IG is performed through a deconstruction and construction phase proposed in the literature that has been proven to be very effective in dealing also with the makespan criterion. Moreover, the algorithms have been tested with three initial solution procedures. The computation of these algorithms when evaluated against an algorithm from the literature has shown their good performance.