Constraint Programming-Based Solution Approaches for Three-Dimensional Loading Capacitated Vehicle Routing Problems
The 3L-CVRP which integrates the three-dimensional loading problem with the capacitated vehicle routing problem. To solve this np-hard problem, we formulated all constraints and objective functions in the context of constraint programming and developed five models: two integrated, two decomposed CP-based, and one decomposed hybrid model. The hybrid model uses a CP model for the routing part and a genetic algorithm for the loading part. First, we compared these models and a MIP model adapted from the literature by solving 24 small-size problems. The hybrid model (CP&EA) gave the highest performance based on the comparison results. Then, a computational study was conducted with Moura and Oliveira's (2009), Bortfeldt and Homberger's (2013) and Gendreau et al. (2006)’s benchmark instances to test the hybrid model's performance in large-size problems. We improved the solution values for 36 of 93 problems and found better results on average than the existing approaches, considering the computational results on bigger problem instances. According to the computational results, Thus, it has been shown that the proposed CP&EA model can help solve the problems in distribution logistics. The related benchmark instances and computational results has been attached the website.