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On Jul 27, 2007, at 2:28 PM, Peter Walker wrote: > 1) (Traditional mutation): select a random node and remove it > (along with all its children) and replace it by a randomly > generated subtree and subtree root. This is ec.gp.koza.Mutation > The other two schemes I would like to implement are based on “point- > mutation”. Both point-mutation schemes would start out by selecting > a node and generate a random node (e.g. symbol1) to replace it. > Symbol1 would be checked to see whether it is of the same arity as > the node. If it is, then the node would be replaced by symbol1. If > they are not of the same arity, then we would either: > > 2) Pick another symbol until we find one of the same arity; OR > > 3) Remove the node and replace it with a new subtree using > symbol1 as the root. You'll need to make a custom mutator for this that FIRST picks a replacement and THEN decides on what to do (#2 or #3). However: - ec.gp.breed.MutateOneNodePipeline will pick another node guaranteed to be of the same arity (and type equivalence) and replace the node with the new node. This is roughly equivalent to #2, as you've noted. - #1 and #3 are roughly equivalent, it'd seem. So I think you'll be writing a custom mutator -- take a look at the code of these classes to get an idea about how to go about doing this (it's nontrivial but doable!) Sean