Genetic algorithms and tabu search: Hybrids for optimization

-Genetic algorithms and tabu search have a number of significant differences. They also have some common bonds, often unrecognized. We explore the nature of the connections between the methods, and show that a variety of opportunities exist for creating hybrid approaches to take advantage of their complementary features. Tabu search has pioneered the systematic exploration of memory functions in search processes, while genetic algorithms have pioneered the implementation of methods that exploit the idea of combining solutions. There is also another approach, related to both of these, that is frequently overlooked. The procedure called scatter search, whose origins overlap with those of tabu search (and roughly coincide with the emergence of genetic algorithms) also proposes mechanisms for combining solutions, with useful features that offer a bridge between tabu search and genetic algorithms. Recent generalizations of scatter search concepts, embodied in notions of structured combinations and path relinkino, have produced effective strategies that provide a further basis for integrating GA and "IS approaches. A prominent TS component called strategic oscillation is susceptible to exploitation by GA processes as a means of creating useful degrees of diversity and of allowing effective transitions between feasible and infeasible regions. The independent success of genetic algorithms and tabu search in a variety of applications suggests that each has features that are valuable for solving complex problems. The thesis of this paper is that the study of methods that may be created from their union can provide useful benefits in diverse settings. 1. I N T R O D U C T I O N Genetic algorithms (GAs) and tabu search (TS) methods are customarily viewed as based on different foundations and perspectives. Although significant differences between the methods exist, the two approaches share certain elements in common that often have been overlooked and left unexploited. The theme of this paper is to identify connections and contrasts between the methods that offer a fertile means for creating hybrid procedures. ?Fred Glover is the US West Chaired Professor in Systems Science at the University of Colorado, Boulder. He has authored or co-authored more than two hundred published articles in the fields of mathematical optimization, computer science and artificial intelligence, with particular emphasis on practical applications in industry and government. In addition to holding editorial posts for journals in the U.S. and abroad. He is co-founder of Optimization Technologies, Inc., Analysis and Research and Computation, Inc., and the nonprofit research organization Decision Analysis and Research Institute. :~James P. Kelly is an Assistant Professor of Management Science in the College of Business and Administration and Graduate School of Business Administration at the University of Colorado in Boulder. He received his doctoral degree in Applied Mathematics and Operations Research from the University of Maryland in 1990. His current research interests are in the area of heuristic combinatorial optimization. Dr Kelly has published several papers on topics such as tabu search and simulated annealing in various journals such as Operations Research and the ORSA Journal on Computing. Currently, he is attempting to use tabu search to construct neural networks for pattern classification. §Manuel Laguna is an Assistant Professor of Operations Management in the College of Business and Administration and Graduate School of Business Administration of the University of Colorado at Boulder. He received master's and doctoral degrees in Operations Research and Industrial Engineering from the University of Texas at Austin. He was the first U S WEST postdoctoral fellow in the Graduate School of Business at the University of Colorado. He has done extensive research in the interface between artificial intelligence and operations research to develop solution methods for problems in the areas of production scheduling, telecommunications, and facility layout. Dr Laguna co-edited the Tabu Search volume of Annals of Operations Research.