Tuesday, November 22, 2011

Genetic Algorithms for non-intuitive solutions

Thinking about evolutionary algorithms and "superstreets" which to me falls into the category of a non-intuitive optimisation.  (In that some actors individually loose while the majority win giving an aggregate win for the system)

This, in my mind is a revolutionary design that would not be developed if the rules were to make the solution "fair" for all the actors in the scenario.   You could probably get a GA to produce it if you had it in mind before you started and tweaked the algo until it was able to do it.

Anyway, my thought was how to give an evolutionary algorithm the ability to not only generate these kinds of non-intuitive solutions but to identify partial solutions that may be worth preserving in the population even though they are not an optimal solution... much like the problem of making a NN explain itself, this is a case of having some "wildcard" model in the population that maintains diversity.  Kind of like the "Island" effect in biology.  Diversity is maintained by seperating the population into small groups that interbreed, with only a little "bleed" around the edges of the groups which allows cross-over of locally optimised mutations.

Another possible strategy is to "lock" mutant sections of the DNA that have high impacts on the overall solution, even if the overall solution may be sub-optimal.  I think this is a flawed strategy because each strategy needs to be evaluated as a whole...

That said, I think an evaluation matrix is better than a summative score, as this allows individual mutations to spike up... which may be the point to move that part of the population to an island and see what develops. 

The question is how to evaluate the solution as in parts... and is this just a different way to arrive at the same flawed solution as above.... trying to "lock" mutations and preserve them artificially.. which defeats the purpose of allowing evolution to act on the population. (Which is all fun as long as its preserving the useful mutations not just plateauing)

Need to run some sims to see what the effect of various strategies might be...

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