The simplest way of achieving this sampling is known as the roulette wheel algorithm. Conceptually this is the same as repeatedly spinning a one-armed roulette wheel, where the sizes of the holes reflect the selection probabilities. In general, the algorithm can be applied to select λ members from the set of μ parents into a mating pool. To illustrate the workings of this algorithm, we will assume some order over the population (ranking or random) from 1 to μ, so that we can calculate the cumulative probability distribution, which is a list of values [a1,a2,...,aμ] such that _=∑26_1^▒〖_ ()〗 , where _ () is defined by the selection distribution — fitness proportionate or ranking. Note that this implies _ = 1. The outlines of the algorithm are given in Fig. 5.1.