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355
Variable neighborhood search: Principles and applications
, 2001
"... Systematic change of neighborhood within a possibly randomized local search algorithm yields a simple and effective metaheuristic for combinatorial and global optimization, called variable neighborhood search (VNS). We present a basic scheme for this purpose, which can easily be implemented using an ..."
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Cited by 198 (15 self)
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Systematic change of neighborhood within a possibly randomized local search algorithm yields a simple and effective metaheuristic for combinatorial and global optimization, called variable neighborhood search (VNS). We present a basic scheme for this purpose, which can easily be implemented using any local search algorithm as a subroutine. Its effectiveness is illustrated by solving several classical combinatorial or global optimization problems. Moreover, several extensions are proposed for solving large problem instances: using VNS within the successive approximation method yields a twolevel VNS, called variable neighborhood decomposition search (VNDS); modifying the basic scheme to explore easily valleys far from the incumbent solution yields an efficient skewed VNS (SVNS) heuristic. Finally, we show how to stabilize column generation algorithms with help of VNS and discuss various ways to use VNS in graph theory, i.e., to suggest, disprove or give hints on how to prove conjectures, an area where metaheuristics do not appear
Iterated local search
 Handbook of Metaheuristics, volume 57 of International Series in Operations Research and Management Science
, 2002
"... Iterated Local Search has many of the desirable features of a metaheuristic: it is simple, easy to implement, robust, and highly effective. The essential idea of Iterated Local Search lies in focusing the search not on the full space of solutions but on a smaller subspace defined by the solutions th ..."
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Cited by 172 (15 self)
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Iterated Local Search has many of the desirable features of a metaheuristic: it is simple, easy to implement, robust, and highly effective. The essential idea of Iterated Local Search lies in focusing the search not on the full space of solutions but on a smaller subspace defined by the solutions that are locally optimal for a given optimization engine. The success of Iterated Local Search lies in the biased sampling of this set of local optima. How effective this approach turns out to be depends mainly on the choice of the local search, the perturbations, and the acceptance criterion. So far, in spite of its conceptual simplicity, it has lead to a number of stateoftheart results without the use of too much problemspecific knowledge. But with further work so that the different modules are well adapted to the problem at hand, Iterated Local Search can often become a competitive or even state of the art algorithm. The purpose of this review is both to give a detailed description of this metaheuristic and to show where it stands in terms of performance. O.M. acknowledges support from the Institut Universitaire de France. This work was partially supported by the “Metaheuristics Network”, a Research Training Network funded by the Improving Human Potential programme of the CEC, grant HPRNCT199900106. The information provided is the sole responsibility of the authors and does not reflect the Community’s opinion. The Community is not responsible for any use that might be made of data appearing in this publication. 1 1
E.: A hyperheuristic approach to scheduling a sales summit. In: Practice and Theory of Automated Timetabling
 III : Third International Conference, PATAT 2000. LNCS
, 2000
"... Abstract. The concept of a hyperheuristic is introduced as an approach that operates at a higher lever of abstraction than current metaheuristic approaches. The hyperheuristic manages the choice of which lowerlevel heuristic method should be applied at any given time, depending upon the characterist ..."
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Cited by 115 (33 self)
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Abstract. The concept of a hyperheuristic is introduced as an approach that operates at a higher lever of abstraction than current metaheuristic approaches. The hyperheuristic manages the choice of which lowerlevel heuristic method should be applied at any given time, depending upon the characteristics of the region of the solution space currently under exploration. We analyse the behaviour of several different hyperheuristic approaches for a realworld personnel scheduling problem. Results obtained show the effectiveness of our approach for this problem and suggest wider applicability of hyperheuristic approaches to other problems of scheduling and combinatorial optimisation.
Local branching
 MATHEMATICAL PROGRAMMING
, 2002
"... The availability of effective exact or heuristic solution methods for general MixedInteger Programs (MIPs) is of paramount importance for practical applications. In the present paper we investigate the use of a generic MIP solver as a blackbox “tactical ” tool to explore effectively suitable solu ..."
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Cited by 91 (9 self)
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The availability of effective exact or heuristic solution methods for general MixedInteger Programs (MIPs) is of paramount importance for practical applications. In the present paper we investigate the use of a generic MIP solver as a blackbox “tactical ” tool to explore effectively suitable solution subspaces defined and controlled at a “strategic” level by a simple external branching framework. The procedure is in the spirit of wellknown local search metaheuristics, but the neighborhoods are obtained through the introduction in the MIP model of completely general linear inequalities called local branching cuts. The new solution strategy is exact in nature, though it is designed to improve the heuristic behavior of the MIP solver at hand. It alternates highlevel strategic branchings to define the solution neighborhoods, and lowlevel tactical branchings to explore them. The result is a completely general scheme aimed at favoring early updatings of the incumbent solution, hence producing highquality solutions at early stages of the computation. The method is analyzed computationally on a large class of very difficult MIP problems by using the stateoftheart commercial software ILOGCplex 7.0 as the blackbox tactical MIP solver. For these instances, most of which cannot be solved to proven optimality in a reasonable time, the new method exhibits consistently an improved heuristic performance: in 23 out of 29 cases, the MIP solver produced significantly better incumbent solutions when driven by the local branching paradigm.
Experimental Investigation of Heuristics for ResourceConstrained Project Scheduling: An Update
, 2004
"... This paper considers heuristics for the well–known resource–constrained project scheduling problem (RCPSP). It provides an update of our survey which was published in 2000. We summarize and categorize a large number of heuristics that have recently been proposed in the literature. Most of these heur ..."
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Cited by 75 (2 self)
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This paper considers heuristics for the well–known resource–constrained project scheduling problem (RCPSP). It provides an update of our survey which was published in 2000. We summarize and categorize a large number of heuristics that have recently been proposed in the literature. Most of these heuristics are then evaluated in a computational study and compared on the basis of our standardized experimental design. Subsequently, we discuss our test design in more detail and give some remarks on its usage by other researchers in future studies. The paper closes with a summary of the recent developments in research on heuristics for the RCPSP.
An Adaptive Large Neighborhood Search Heuristic for the Pickup and Delivery Problem with Time Windows
 TRANSPORTATION SCIENCE
, 2006
"... The pickup and delivery problem with time windows is the problem of serving a number of transportation requests using a limited amount of vehicles. Each request involves moving a number of goods from a pickup location to a delivery location. Our task is to construct routes that visit all locations s ..."
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Cited by 67 (5 self)
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The pickup and delivery problem with time windows is the problem of serving a number of transportation requests using a limited amount of vehicles. Each request involves moving a number of goods from a pickup location to a delivery location. Our task is to construct routes that visit all locations such that corresponding pickups and deliveries are placed on the same route and such that a pickup is performed before the corresponding delivery. The routes must also satisfy time window and capacity constraints. This paper presents a heuristic for the problem based on an extension of the Large Neighborhood Search heuristic previously suggested for solving the vehicle routing problem with time windows. The proposed heuristic is composed of a number of competing subheuristics which are used with a frequency corresponding to their historic performance. This general framework is denoted Adaptive Large Neighborhood Search. The heuristic is tested on more than 350 benchmark instances with up to 500 requests. It is able to improve the best known solutions from the literature for more than 50 % of the problems. The computational experiments indicate that it is advantageous to use several competing subheuristics instead of just one. We believe that the proposed heuristic is very robust and is able to adapt to various instance characteristics.
Iterated Local Search for the Quadratic Assignment Problem
 FG INTELLEKTIK, FB INFORMATIK
, 1999
"... Iterated local search (ILS) is a surprisingly simple but at the same time powerful metaheuristic for finding high quality approximate solutions for combinatorial optimization problems. ILS is based on the repeated application of a local search algorithm to initial solution which are obtained by m ..."
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Cited by 61 (10 self)
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Iterated local search (ILS) is a surprisingly simple but at the same time powerful metaheuristic for finding high quality approximate solutions for combinatorial optimization problems. ILS is based on the repeated application of a local search algorithm to initial solution which are obtained by mutations of previously found local optima  in most ILS algorithms these mutations are applied to the best found solution since the start of the search. In this article we present and analyze the application of ILS to the quadratic assignment problem (QAP). We first justify the potential usefulness of an ILS approach to this problem by an analysis of the QAP search space. An investigation of the runtime behavior of the ILS algorithm reveals a stagnation behavior of the algorithm  it may get stuck for many iterations in local optima. To avoid such stagnation situations we propose enhancements of the ILS algorithm based on extended acceptance criteria as well as populationbased...
A Classification of Hyperheuristic Approaches
"... The current state of the art in hyperheuristic research comprises a set of approaches that share the common goal of automating the design and adaptation of heuristic methods to solve hard computational search problems. The main goal is to produce more generally applicable search methodologies. In ..."
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Cited by 58 (21 self)
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The current state of the art in hyperheuristic research comprises a set of approaches that share the common goal of automating the design and adaptation of heuristic methods to solve hard computational search problems. The main goal is to produce more generally applicable search methodologies. In this chapter we present and overview of previous categorisations of hyperheuristics and provide a unified classification and definition which captures the work that is being undertaken in this field. We distinguish between two main hyperheuristic categories: heuristic selection and heuristic generation. Some representative examples of each category are discussed in detail. Our goal is to both clarify the main features of existing techniques and to suggest new directions for hyperheuristic research.
JMeans: A New Local Search Heuristic for Minimum SumofSquares Clustering
"... A new local search heuristic, called JMeans, is proposed for solving the minimum sumofsquares clustering problem. The neighborhood of the current solution is defined by all possible centroidtoentity relocations followed by corresponding changes of assignments. Moves are made in such neighborhoo ..."
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Cited by 52 (10 self)
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A new local search heuristic, called JMeans, is proposed for solving the minimum sumofsquares clustering problem. The neighborhood of the current solution is defined by all possible centroidtoentity relocations followed by corresponding changes of assignments. Moves are made in such neighborhoods until a local optimum is reached. The new heuristic is compared with two other wellknown local search heuristics, KMeans and HMeans as well as with HMeans+, an improved version of the latter in which degeneracy is removed. Moreover, another heuristic, which fits into the Variable Neighborhood Search metaheuristic framework and uses JMeans in its local search step, is proposed too. Results on standard test problems from the literature are reported. It appears that JMeans outperforms the other local search methods, quite substantially when many entities and clusters are considered. 1 Introduction Consider a set X = fx 1 ; : : : ; xN g, x j = (x 1j ; : : : ; x qj ) 2 R q of N entiti...
B.: A hybrid heuristic ordering and variable neighbourhood search for the nurse rostering problem
 European Journal of Operational Research
"... This paper is concerned with the development of intelligent decision support methodologies for nurse rostering problems in large modern hospital environments. We present an approach which hybridises heuristic ordering with variable neighbourhood search. We show that the search can be extended and th ..."
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Cited by 47 (26 self)
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This paper is concerned with the development of intelligent decision support methodologies for nurse rostering problems in large modern hospital environments. We present an approach which hybridises heuristic ordering with variable neighbourhood search. We show that the search can be extended and the solution quality can be significantly improved by the careful combination and repeated use of heuristic ordering, variable neighbourhood search and backtracking. The amount of computational time that is allowed plays a significant role and we analyse and discuss this. The algorithms are evaluated against a commercial Genetic Algorithm on commercial data. We demonstrate that this methodology can significantly outperform the commercial algorithm. This paper is one of the few in the scientific nurse rostering literature which deal with commercial data and which compare against a commercially implemented algorithm.