Please remove me from email as I am not using your system.
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---------- Original message ----------------------
From: Sean Luke <[log in to unmask]>
> 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!)