Roulette-wheel selection, also called fitness-proportionate selection, chooses genetic-algorithm chromosomes with probabilities proportional to their fitness. Every chromosome can be selected, while fitter chromosomes receive larger portions of the wheel. section 5.3
Selection in a generic genetic algorithm
A configurable GeneticAlgorithm can select either roulette or tournament mode. In roulette mode, it builds one probability share per cached fitness value, then repeatedly picks parents with pickRoulette.



