Out-of-the-Box and Custom Implementation of Metaheuristics. A Case Study: The Vehicle Routing Problem with Stochastic Demand

Metaheuristics are a class of effective algorithms for optimization problems. A basic implementation of a metaheuristic typically requires rather little development effort. With a significantly larger investment in the design, implementation, and fine-tuning, metaheuristics can often produce state-of-the-art results. According to the amount of development effort, we say that an implementation of a metaheuristic is either an out-of-the-box version or a custom one. The possibility of implementing metaheuristics in such a flexible way is one of the major strengths of these algorithms. Nonetheless, it also hides some possible catches. In particular, it should be noticed that results obtained with out-of-the-box implementations cannot be always generalized to custom ones, and vice versa. The goal of this analysis is to stress that these two ways of using metaheuristics are different. As a case study, we focus on the vehicle routing problem with stochastic demand and on five among the most successful metaheuristics—namely, tabu search, simulated annealing, genetic algorithms, iterated local search, and ant colony optimization. We show that the relative performance of these algorithms strongly varies whether one considers out-of-the-box implementations or custom ones, in which the parameters are accurately fine-tuned. Moreover, we underline the relevance of clearly stating the framework in which the results reported in the literature have been obtained. To this aim, we consider also an implementation of the same algorithms as described in the literature. Paola Pellegrini Department of Applied Mathematics, Università Ca’ Foscari Venezia, Cannaregio 873, 30121, Venice, Italy e-mail: paolap@unive.it Mauro Birattari IRIDIA, CoDE, Université Libre de Bruxelles, 50, Av. F. Roosevelt, CP 194/6, B-1050 Brussels, Belgium e-mail: mbiro@ulb.ac.be M. Köppen et al. (Eds.): Intelligent Comput. Optimization in Eng., SCI 366, pp. 273–295. springerlink.com c © Springer-Verlag Berlin Heidelberg 2011 274 P. Pellegrini and M. Birattari