All of the selection strategies require the number to be specified as an
argument to the select method, so it depends on the implementation of the
EvolutionEngine that you are using. For the GenerationalEvolutionEngine,
this is the size of the population (less the number of individuals that
have been preserved by elitism), so that the size of the population is
constant from generation to generation. The SteadyStateEvolutionEngine on
the other hand typically only selects one or two individuals at a time.
If you want to alter the selection behaviour of any of the evolution
engines, you would have to sub-class it and over-ride the
nextEvolutionStep method.
Dan.
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Daniel Dyer