In a genetic algorithm, when selecting members for crossover using roulette-wheel selection method, does the population first need to be sorted by fitness rank?
The possibilities seem to be:
- sort population first by ascending fitness
- sort population by descending fitness
- don't sort population & let the roulette ball fall where it may..
I'm thinking that sorting either way may have no effect – a pebble landing at random on a wheel containing different sized (by fitness) slices will have exactly the same outcome chance whether the larger slices are grouped together or not. But I'm not 100% convinced.
What do you think?
The need to do a sort every generation affects the speed of the algorithm too, so I'd prefer not to (I would do a sort if using elitism, but I'm not in this case).
Thanks if you know, as I cannot find a definitive answer via google etc..