Computational Intelligence

80 Chapter Three—Evolutionary Computation Concepts and Paradigms

each individual engages in n-1 unique tournaments, where n is the population size,

is exactly equivalent to ranking.

Differences exist between evolution strategies and other paradigms of evolu-

tionary computation with respect to selection. ESs generally operate with a surplus

of descendants. Schwefel (1994) describes the most common versions of ES selec-

tion, known as the (

μ, λ) and (μ + λ) ES. In both versions, the number of children

generated from

μ parents is λ > μ. Commonly used is a λ/μ ratioof7.Inthe

original (1 + 1) ES, one parent produces one offspring, with only the fitter of ...