More Concise and Robust Linkage Learning by Filtering and Combining Linkage Hierarchies

Genepool Optimal Mixing Evolutionary Algorithms (GOMEAs) were recently proposed as a new way of designing linkage-friendly, efficiently-scalable evolutionary algorithms (EAs). GOMEAs combine the building of linkage models with an intensive, greedy mixing procedure. Recent results indicate that the use of hierarchical linkage models in GOMEAs lead to the most robust and efficient performance. Two of such GOMEA instances are the Linkage Tree Genetic Algorithm (LTGA) and the Multi-scale Linkage Neighbors Genetic Algorithm (MLNGA). The linkage models in these GOMEAs have their individual merits and drawbacks. In this paper, we propose enhancement techniques targeted at filtering out superfluous linkage sets from hierarchical linkage models and we consider a way to construct a linkage model that combines the strengths of different linkage models. We then propose a new GOMEA instance, called the Linkage Trees and Neighbors Genetic Algorithm (LTNGA), that combines the models of LTGA and MLNGA. LTNGA performs comparable or better than the best of either LTGA or MLNGA on various problems, including typical linkage benchmark problems and instances of the well-known combinatorial problem MAXCUT, especially when the proposed filtering techniques are used.