An efficient hybrid iterated local search algorithm for the total tardiness blocking flow shop problem

This paper deals with the blocking flow shop problem and proposes an Iterated Local Search (ILS) procedure combined with a variable neighbourhood search (VNS) for the total tardiness minimization. The proposed ILS makes use of a NEH-based procedure to generate the initial solution, uses a local search to intensify the exploration which combines the insertion and swap neighbourhood and uses a perturbation mechanism that applies, d times, three neighbourhood operators to the current solution to diversify the search. The computational evaluation has shown that the insertion neighbourhood is more effective than the swap one, but it also has shown that the combination of both is a good strategy to improve the obtained solutions. Finally, the comparison of the ILS with an Iterated greedy algorithm and with a greedy randomized adaptive search procedure has revealed its good performance.