In recent years, the field of combinatorial optimization has witnessed a true tsunami of "novel" metaheuristic methods, most of them based on a metaphor of some natural or man-made process. The behavior of virtually any species of insects, the flow of water, musicians playing together -it seems that no idea is too far-fetched to serve as inspiration to launch yet another metaheuristic. In this paper, we will argue that this line of research is threatening to lead the area of metaheuristics away from scientific rigor. We will examine the historical context that gave rise to the increasing use of metaphors as inspiration and justification for the development of new methods, discuss the reasons for the vulnerability of the metaheuristics field to this line of research, and point out its fallacies. At the same time, truly innovative research of high quality is being performed as well. We conclude the paper by discussing some of the properties of this research and by pointing out some of the most promising research avenues for the field of metaheuristics.The infamous Higgs boson that gives other particles their mass is, of course, the "salt" particle in the new theory, which gives other "dishes" their "flavor."There is not much doubt that the reaction of the scientific community over this article would be one of ridicule, if not outrage. In letters to the editor (who would probably be fired for allowing this article to be published), the question would rightfully be asked whether any new contribution was made other than a re-iteration of existing knowledge. The authors would be widely criticized for their attempt to change the vocabulary of the standard theory of particle physics, a tool that has been instrumental in allowing scientists across the world to communicate unambiguously. Steps would certainly be taken for this type of "research" never to be published again in a reputable journal.The above story may strike the reader as very unlikely, yet it is not as far-fetched as it may seem at first sight. On the contrary, in the research field of optimization using metaheuristics, contributions akin to the hypothetical paper described above are frighteningly common. For a few decades, every year has seen the publication of several papers claiming to present a "novel" method for optimization, based on a metaphor of a process that is often seemingly completely unrelated to optimization. The jumps of frogs, the refraction of light, the flowing of water to the sea, an orchestra playing, sperm cells moving to fertilize an egg, the spiraling movements of galaxies, the colonizing behavior of empires, the behavior of bats, birds, ants, bees, flies, and virtually every other species of insects -it seems that there is not a single natural or man-made process that cannot be used as a metaphor for yet another "novel" optimization method. Invariably, the authors of such papers promise that their "new" method is superior to methods previously published in the literature. Rather than being scorned for the reasons mentioned above, mor...

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The traveling repairman problem is a customer-centric routing problem, in which the total waiting time of the customers is minimized, rather than the total travel time of a vehicle. To date, research on this problem has focused on exact algorithms and approximation methods. This paper presents the first metaheuristic approach for the traveling repairman problem. Keywords

Purpose The growth of e-commerce is accompanied by an increasing distribution of parcels in cities resulting in externalities like traffic congestion or emissions. As a consequence, different delivery concepts like bike deliveries or delivery points have been suggested. Naturally, companies will only accept these changes, if they do not result in higher costs. However, it is difficult to predict the impact of a certain delivery concept in a certain city. This leads to the research question, how different delivery scenarios for a certain area can be assessed and compared, especially if some of them have not been implemented. Methods Using a case study, we demonstrate how the effects of different delivery concepts can be quantified with the help of a simulation study. We take care to accurately model the delivery processes and utilise a real-world dataset and realistic cost values. On the basis of these inputs, we simulate and analyse the current state-of-the-practice in the distribution of e-commerce goods in Antwerp and compare it to possible`what-if' scenarios. Results The results highlight that the investigated delivery concepts can benefit either the companies or the quality of life in the city. Operational costs of companies can be reduced by stimulating customer self-pick-up, while externalities decrease with the implementation of a cargo bike distribution system. Conclusions We demonstrate that both operational and external costs can be minimised, if involved stakeholders from industry and the public look for sustainable delivery solution jointly.

When entering a horizontal logistics alliance, companies can expect a significant cost decrease. In this paper, we show that when the partners in an alliance adopt a flexible attitude (i.e. allow changes to the terms of their deliveries), the total cost can be further decreased. We argue that the method used to allocate the total cost to the different partners should therefore encourage such flexibility. A case study of three companies in Belgium achieves a 25.83% decrease in transportation costs. Allocating this collaborative gain with the Shapley value, the individual gains range from 19.01% to 37.56%. By allowing changes to delivery dates and allowing large orders to be split into several deliveries, the partners in the alliance can increase the collaborative gain and their individual gains. The Shapley value is found to encourage flexibility.

a b s t r a c tThis paper proposes a variant of the well-known capacitated vehicle routing problem that models the routing of vehicles in the cash-in-transit industry by introducing a risk constraint. In the Risk-constrained Cash-inTransit Vehicle Routing Problem (RCTVRP), the risk of being robbed, which is assumed to be proportional both to the amount of cash being carried and the time or the distance covered by the vehicle carrying the cash, is limited by a risk threshold.A library containing two sets of instances for the RCTVRP, some with known optimal solution, is generated. A mathematical formulation is developed and small instances of the problem are solved by using IBM CPLEX.Four constructive heuristics as well as a local search block composed of six local search operators are developed and combined using two different metaheuristic structures: a multistart heuristic and a perturband-improve structure. In a statistical experiment, the best parameter settings for each component are determined, and the resulting heuristic configurations are compared in their best possible setting. The resulting metaheuristics are able to obtain solutions of excellent quality in very limited computing times.

This chapter describes the history of metaheuristics in five distinct periods, starting long before the first use of the term and ending a long time in the future. *

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