Influence of Topological Features on Spatially-Structured Evolutionary Algorithms Dynamics
This work addresses the impact of network structures on evolutionary algorithms for researchers in optimization, though it is incremental in exploring specific topological features.
The study investigated how different network topologies affect the performance of a spatially-structured evolutionary algorithm on multi-modal optimization problems, finding that networks with large average path length increased the number of optima found but slowed exploration dynamics, and that weighted networks allowed tuning of algorithm behavior during execution.
In the last decades, complex networks theory significantly influenced other disciplines on the modeling of both static and dynamic aspects of systems observed in nature. This work aims to investigate the effects of networks' topological features on the dynamics of an evolutionary algorithm, considering in particular the ability to find a large number of optima on multi-modal problems. We introduce a novel spatially-structured evolutionary algorithm and we apply it on two combinatorial problems: ONEMAX and the multi-modal NMAX. Considering three different network models we investigate the relationships between their features, algorithm's convergence and its ability to find multiple optima (for the multi-modal problem). In order to perform a deeper analysis we investigate the introduction of weighted graphs with time-varying weights. The results show that networks with a large Average Path Length lead to an higher number of optima and a consequent slow exploration dynamics (i.e. low First Hitting Time). Furthermore, the introduction of weighted networks shows the possibility to tune algorithm's dynamics during its execution with the parameter related with weights' change. This work gives a first answer about the effects of various graph topologies on the diversity of evolutionary algorithms and it describes a simple but powerful algorithmic framework which allows to investigate many aspects of ssEAs dynamics.