Selective pressure in evolutionary algorithms: a characterization of selection mechanisms

Due to its independence of the actual search space and its impact on the exploration-exploitation tradeoff, selection is an important operator in any kind of evolutionary algorithm. All important selection operators are discussed and quantitatively compared with respect to their selective pressure. The comparison clarifies that only a few really different and useful selection operators exist: proportional selection (in combination with a scaling method), linear ranking, tournament selection, and (μ,λ)-selection (respectively (μ+λ)-selection). Their selective pressure increases in the order as they are listed here. The theoretical results are confirmed by an experimental investigation using a genetic algorithm with different selection methods on a simple unimodal objective function