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The maximum diversity problem (MDP) consists of identifying optimally diverse subsets of elements from some larger collection. The selection of elements is based on the diversity of their characteristics, calculated by a function applied on their attributes. This problem belongs to the class of NP-hard problems. This paper presents new GRASP heuristics for… (More)

Nowadays genetic algorithms stand as a trend to solve NP-complete and NP-hard problems. In this paper, we present a new hybrid metaheuristic which uses Parallel Genetic Algorithms and Scatter Search coupled with a decomposition-into-petals procedure for solving a class of Vehicle Routing and Scheduling Problems. The parallel genetic algorithm presented is… (More)

This paper deals with the Heterogeneous Fleet Vehicle Routing Problem (HFVRP). The HFVRP is N P-hard since it is a generalization of the classical Vehicle Routing Problem (VRP), in which clients are served by a heterogeneous fleet of vehicles with distinct capacities and costs. The objective is to design a set of routes in such a way that the sum of the… (More)

This paper deals with the Heterogeneous Fleet Vehicle Routing Problem (HFVRP). The HFVRP generalizes the classical Capacitated Vehicle Routing Problem by considering the existence of different vehicle types, with distinct capacities and costs. The objective is to determine the best fleet composition as well as the set of routes that minimize the total… (More)

This work presents an integer programming formulation for a variant of the Class-Teacher Timetabling problem, which considers the satisfaction of teacher preferences and also the proper distribution of lessons throughout the week. The formulation contains a very large number of variables and is enhanced by cuts. Therefore, a cut and column generation… (More)

The Class/Teacher Timetabling Problem (CTTP) deals with the weekly scheduling of encounters between teachers and classes of an educational institution. Since CTTP is a NP-hard problem for nearly all of its variants, the use of heuristic methods for its resolution is justified. This paper presents an efficient Tabu Search (TS) heuristic with two different… (More)

The Maximum Diversity Problem (MDP) consists in identifying , in a population, a subset of elements, characterized by a set of attributes, that present the most diverse characteristics between themselves. The identification of such solution is an NP-hard problem. Some heuristics are available to obtain approximate solutions for this problem. In this paper… (More)

This paper presents an asynchronous parallel metaheuristic for the period vehicle routing problem (PVRP). The PVRP generalizes the classical vehicle routing problem by extending the planning period from a single day to M days. The algorithm proposed is based on concepts used in parallel genetic algorithms and local search heuristics. The algorithm employs… (More)