47 research outputs found
A study on exponential-size neighborhoods for the bin packing problem with conflicts
We propose an iterated local search based on several classes of local and
large neighborhoods for the bin packing problem with conflicts. This problem,
which combines the characteristics of both bin packing and vertex coloring,
arises in various application contexts such as logistics and transportation,
timetabling, and resource allocation for cloud computing. We introduce
evaluation procedures for classical local-search moves, polynomial variants of
ejection chains and assignment neighborhoods, an adaptive set covering-based
neighborhood, and finally a controlled use of 0-cost moves to further diversify
the search. The overall method produces solutions of good quality on the
classical benchmark instances and scales very well with an increase of problem
size. Extensive computational experiments are conducted to measure the
respective contribution of each proposed neighborhood. In particular, the
0-cost moves and the large neighborhood based on set covering contribute very
significantly to the search. Several research perspectives are open in relation
to possible hybridizations with other state-of-the-art mathematical programming
heuristics for this problem.Comment: 26 pages, 8 figure
A Neighborhood Exploration Approach with Multi-start for Extend Generalized Block-modeling
International audienc
An iterated local search heuristic for the heterogeneous fleet vehicle routing problem.
This paper deals with the Heterogeneous Fleet Vehicle Routing Problem
(HFVRP). The HFVRP is NP-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 costs is minimized. The proposed algorithm is
based on the Iterated Local Search (ILS) metaheuristic which uses a Variable Neighborhood
Descent procedure, with a random neighborhood ordering (RVND), in the
local search phase. To the best of our knowledge, this is the first ILS approach for
the HFVRP. The developed heuristic was tested on well-known benchmark instances
involving 20, 50, 75 and 100 customers. These test-problems also include dependent
and/or fixed costs according to the vehicle type. The results obtained are quite competitive
when compared to other algorithms found in the literature
An ils-based heuristic applied to the car renter salesman problem
The present paper tackles the Car Renter Salesman Problem (CaRS), which is a Traveling Salesman Problem variant. In CaRS, the goal is to travel through a set of cities using rented vehicles at minimum cost. The main aim of the current problem is to establish an optimal route using rented vehicles of different types to each trip. Since CaRS is N P-Hard, we herein present a heuristic approach to tackle it. The approach is based on a Multi-Start Iterated Local Search metaheuristic, where the local search step is based on the Random Variable Neighborhood Descent methodology. An Integer Linear Programming Formulation based on a Quadratic Formulation from literature is also proposed in the current study. Computational results for the proposed heuristic method in euclidean instances outperform current state-of-the-art results. The proposed formulation also has stronger bounds and relaxation when compared to others from literature
Uma heur?stica para o problema de programa??o de hor?rios em escolas.
Apresentamos GBT-II, uma heur?stica para resolver problemas de programa??o de hor?rios em escolas. A partir de uma solu??o inicial gerada por um procedimento construtivo parcialmente guloso, um procedimento de Busca Tabu inicia sua pesquisa. Quando uma solu??o sem sobreposi??es, mas com, possivelmente, algum outro tipo de inviabilidade, ? gerada, acionamos um procedimento chamado intraturmas-Intertumas para tentar recuperar a viabilidade. Sendo bem sucedido, ele ? novamente acionado, agora para tentar melhorar a capacidade da agenda dos professores, bem como outras medidas de qualidade. Ap?s um certo n?mero de intera??es sem melhora, todo o processo, desde a gera??o de uma solu??o inicial, ? repetido at? que uma condi??o de parada seja satisfeita . Resultados computacionais mostram que a tiliza??o do procedimento Intraturmas-Interturmas faz produzir solu??es melhores rapidamente