selection.py: add fitness_greedy param to selDoubleTournament #726
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This adds an element of elitism to the size tournament, so that parsimony pressure only applies when fitnesses are tied. The default behaviour (fitness_greedy=False) is the same as the old behaviour, since it may not be helpful in all circumstances.
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I've added a small tweak to
selDoubleTournamentwhich allows adding elitism to the size tournament, so that parsimony pressure only applies when fitnesses are equal. The default behaviour (fitness_greedy=False) is the same as the old behaviour, since it may not be helpful in all circumstances.I've found it converges much quicker and more reliably on a minimisation problem with an integer-valued fitness function. It may be terrible with continuous fitnesses where a tie is rare. Perhaps it would be better to use an epsilon parameter and let the size tournament behave as normal unless the fitnesses are within some distance
dof each other? I'd be interested to hear your thoughts.