The contribution of infeasible solutions in heuristic searches for vehicle routing problems does not make, up to date, a consensus in the metaheuristics community. In one hand, infeasible solutions may allow to transition between structurally different feasible solutions, thus enhancing the search. In the other hand they also lead to more complex move evaluation procedures and in wider search s...

This extended abstract presents a synthesis of our work concerning a parallel algorithm for Vehicle Routing Problem with Time Windows (VRPTW). Two colonies work in parallel and cooperate to solve the problem, each one being charged with an objective of the optimization. In addition, the importance of these objectives can vary, depending on some environmental changes. This approach introduces a ...

The analytic center cutting plane method (ACCPM) is one of successful methods to solve nondifferentiable optimization problems. In this paper, ACCPM is used to accelerate Lagrangian relaxation procedure for solving a vehicle routing problem with time windows (VRPTW). First, a basic cutting plane algorithm and its relationship with a column generation technique is clarified. Then, the proposed m...

This paper presents a parallel memetic algorithm for solving the vehicle routing problem with time windows (VRPTW). The VRPTW is a well-known NP-hard discrete optimization problem with two objectives. The main objective is to minimize the number of vehicles serving customers scattered on the map, and the second one is to minimize the total distance traveled by the vehicles. Here, the fleet size...

The Vehicle Routing Problem with Time Windows is a complex combinatorial optimization problem which can be seen as a fusion of two well known sub-problems: the Travelling Salesman Problem and the Bin Packing Problem. Its main objective is to find the lowest-cost set of routes to deliver demand, using identical vehicles with limited capacity, to customers with fixed service time windows. In this...

In [1] we introduced a new state-space relaxation, called ng-path relaxation, to compute lower bounds to routing problems, such as the Capacitated Vehicle Routing Problem (CVRP) and the VRP with Time Windows (VRPTW). This relaxation consists of partitioning the set of all possible paths ending at a generic vertex according to a mapping function that associates with each path a subset of the vis...

The elementary shortest path problem with resource constraints (ESPPRC) is a widely used modeling tool in formulating vehicle routing and crew scheduling applications, see e.g. [3]. The ESPPRC consists of finding shortest paths from a source to all other nodes of a network that do not contain any cycles, i.e. duplicate nodes. The ESPPRC occurs as a subproblem of an enclosing problem and is used...

the location-routing problem is a relatively new branch of logistics system. its objective is to determine a suitable location for constructing distribution warehouses and proper transportation routing from warehouse to the customer. in this study, the location-routing problem is investigated with considering fuzzy servicing time window for each customer. another important issue in this regard ...

In many applications of the vehicle routing problem with time windows(VRPTW), the primary objective is defined as the minimization of the number of routes or vehicles. Minimization of the total travel cost is introduced as a secondary objective. Recently, it has been recognized that minimizing the number of routes and the travel cost concurrently often drives a search toward solutions with low ...