Variable neighbourhood search (VNS) is a metaheuristic, or a framework for building heuristics, based upon systematic changes of neighbourhoods both in descent phase, to find a local minimum, and in perturbation phase to emerge from the corresponding valley. It was first proposed in 1997 and has since then rapidly developed both in its methods and its applications. In the present paper, these t...

Nurse rostering problems consist of assigning varying tasks, represented as shift types, to hospital personnel with different skills and work regulations. We want to satisfy as many constraints and personal preferences as possible while constructing a schedule which meets the personnel requirements of the hospital over a predefined planning period. Real world situations are often so constrained...

Simulated annealing is a general optimisation algorithm, based on hill-climbing. As in hill-climbing, new candidate solutions are selected from the ‘neighbourhood’ of the current solution. For continuous parameter optimisation, it is practically impossible to choose direct neighbours, because of the vast number of points in the search space. In this case, it is necessary to choose new candidate...

Many successful approaches to examination timetabling consist of multiple stages, in which a constructive approach is used for finding a good initial solution, and then one or more improvement approaches are employed successively to further enhance the quality of the solution obtained during the previous stage. Moreover, there is a growing number of studies describing the success of approaches ...

Many successful approaches to examination timetabling consist of multiple stages, in which a constructive approach is used for finding a good initial solution, and then one or more improvement approaches are employed successively to further enhance the quality of the solution obtained during the previous stage. Moreover, there is a growing number of studies describing the success of approaches ...

The classical vehicle routing problems are designed for distance or cost reduction. The routes generated by the model will be insensitive towards the environmental impact. In this work, a green vehicle routing problem is addressed. A metaheuristic algorithm combining an Ant Colony Optimization algorithm with a Variable Neighbourhood Search algorithm is developed to solve the problem. The hybrid...

The response time variability problem (RTVP) is a scheduling problem that arises whenever products, clients or jobs need to be sequenced in such a way that the variability in the time between the instants at which they receive the necessary resources is minimised. The RTVP is an NP-hard problem and heuristic and metaheuristic techniques are needed to solve non-small instances. The best results ...

In this work we consider an hybrid metaheuristic approach to solve the Strip Packing Problem. In the hybrid algorithm, we use an Variable Neighbourhood Search (VNS) to improve the quality of part of the solution obtained with a Greedy Randomized Adaptive Search Procedure (GRASP). Then, the results achieved with the hybrid method are compared with those existing in the literature. From these res...

Neighbourhood structure and size are important parameters in local search algorithms. This is also true for generalised local search algorithms like simulated annealing. It has been shown that the performance of simulated annealing can be improved by adopting a suitable neighbourhood size. However, previous studies usually assumed that the neighbourhood size was xed during search. This paper pr...