The genetic algorithm behaviour is determined by the exploitation and exploration relationship kept throughout the run. Adaptive genetic algorithms, that dynamically adjust selected control parameters or genetic operators during the evolution have been built. Their objective is to offer the most appropriate exploration and exploitation behaviour to avoid the premature convergence problem and improve the final results. One of the adaptive approaches are the adaptive parameter setting techniques based on the use of fuzzy logic controllers, the fuzzy adaptive genetic algorithms (FAGAs). In this paper, we analyse the FAGAs in depth. First, we describe the steps for their design and present an instance, which is studied from an empirical point of view. Then, we propose a taxonomy for FAGAs, attending on the combination of two aspects: the level where the adaptation takes place and the way the Rule-Bases are obtained. Furthermore, FAGAs belonging to different groups of the taxonomy are reviewed. Finally, we identify some open issues, and summarise a few new promising research directions on the topic. From the results provided by the approaches presented in the literature and the experimental results achieved in this paper, an important conclusion is obtained: the use of fuzzy logic controllers to adapt genetic algorithm parameters may really improve the genetic algorithm performance.Keywords Adaptive genetic algorithms, Fuzzy logic controllers
IntroductionThe behaviour of the genetic algorithms (GAs) [25] is strongly determined by the balance between exploration (to investigate new and unknown areas in a search space) and exploitation (to make use of knowledge acquired by exploration to reach better positions on the search space). The GA control parameter settings, such as mutation probability, crossover probability, and population size, are key factors in the determination of the exploitation versus exploration tradeoff. It has long been acknowledged that they have a significant impact on GA performance [28]. If poor settings are used, the exploration/exploitation balance may not be reached in a profitable way; the GA performance shall be severely affected due to the possibility of premature convergence.Finding robust control parameter settings is not a trivial task, since their interaction with GA performance is a complex relationship and the optimal ones are problemdependent [4]. Furthermore, different control parameter values may be necessary during the course of a run to induce an optimal exploration/exploitation balance. For these reasons, adaptive GAs (AGAs) have been built that dynamically adjust selected control parameters or genetic operators during the course of evolving a problem solution. Their objective is to offer the most appropriate exploration and exploitation behaviour [1,19,22,31,47,53].Fuzzy logic controllers (FLCs) [17] provide a tool which can convert the linguistic control strategy based on expert knowledge into an automatic control strategy. They are particularly suited to model the relationshi...