An interactive GRAMPS algorithm for the heterogeneous fixed fleet vehicle routing problem with and without backhauls

In this article, a visual interactive approach based on a new greedy randomised adaptive memory programming search (GRAMPS) algorithm is proposed to solve the heterogeneous fixed fleet vehicle routing problem (HFFVRP) and a new extension of the HFFVRP, which is called heterogeneous fixed fleet vehicle routing problem with backhauls (HFFVRPB). This problem involves two different sets of customers. Backhaul customers are pickup points and linehaul customers are delivery points that are to be serviced from a single depot by a heterogeneous fixed fleet of vehicles, each of which is restricted in the capacity it can carry, with different variable travelling costs. The proposed approach is implemented within a visual decision support system, which was developed to allow users to produce and judge alternative decisions by using their knowledge and experience about the requirements of the HFFVRP. The computational results are provided on classical problem instances for HFFVRP and a new best-known solution has been reported. A new set of problem instances for HFFVRPB is proposed. The results show that the proposed approach can find high quality solutions in very short time and the system is able to create alternative solutions in order to satisfy the user's expectations.Routing Metaheuristics GRAMPS Heterogeneous fixed fleet Backhauls

Continuous review inventory control in the presence of fuzzy costs

This paper presents new models of continuous review inventory control with or without backorder in the presence of uncertainty. Fuzzy set concepts are used to treat imprecision regarding the costs of continuous review inventory control, while probability theory is used to treat uncertainty regarding customer demand. Fuzzy total annual cost functions, which involve fuzzy arithmetic operations, are defined using the function principle. The optimal order quantity and the optimal reorder point are found in such a way as to minimize the fuzzy costs. Furthermore, a decision support system has been developed, which can be used for efficient evaluation of continuous review inventory systems with both crisp and fuzzy costs, incorporating a simulation analysis tool.

A visual interactive approach to classical and mixed vehicle routing problems with backhauls

In this paper a new visual interactive approach for the classical vehicle routing problem with backhauls (VRPB) and its extensions is presented. The classical VRPB is the problem of designing minimum cost routes from a single depot to two type customers that are known as Backhaul (pickup) and Linehaul (delivery) customers where deliveries after pickups are not allowed. The mixed VRPB is an extension of the classical VRPB where deliveries after pickups are allowed. A decision support system (DSS) is developed in order to solve the classical VRPB, mixed VRPB and the restricted VRPB, which is a compromise problem between the classical VRPB, and the mixed VRPB. And a new criterion, which considers the remaining capacity of the vehicles, is proposed for producing solutions for mixed and restricted VRPB. The visual interactive approach that is based on Greedy Randomised Adaptive Memory Programming Search (GRAMPS) is described, and experimental results for the VRPB benchmark test problems are presented and analysed. The computational results on VRPB benchmark test problems indicated that the new criterion and the proposed visual interactive approach are effective towards finding a compromise between the mixed or restricted and the classical VRPB problems. The developed DSS is used by 18 students and reported to be capable of producing high quality solutions for the VRPB.Vehicle routing Backhauls Heuristics Decision support systems