quote: Original post by Optikal

quote: Original post by fup
It sounds to me that ''niching'' would just be a technique used to increase the selection intensity of your GA at the cost of exploration. This is not necessarily a bad thing, so long as you understand the consequences. It will cause your GA to converge quicker, but the risks of getting stuck in local optimums also increases. Without doing too much research in this area, I would be inclined to say that there are easier/less complex ways to increase the selection intensity without having to add the complexity of niching.

Speciation will not cause a population to converge quicker or increase the risk of it getting stuck in local minima/maxima. In fact it will do the complete opposite. That''s the whole point. Speciation helps to protect innovation in the genomes.

The reasoning behind my comment was that niching imposes restrictions on which individuals can reproduce with each other. It would seem to me, that removing these restrictions would increase the exploration of the GA (regardless of how well thought out those restrictions are). It will essentially provide an influence over which way the solutions evolve, whereas without these restrictions the way they evolve would be pretty random which would be more exploratory. Please explain further if I have misunderstood, I am interested in this stuff.

actually, now that you explain it that way... or now that I am awake enough to understand... what you are saying makes very much sence... It seems like having a single population will have a tendancy to find local minimum... due to the fact that they all end up being intermixed... it makes it hard for multipule places in the search space to develop. I am not sure what the effect of this would be, but it seems that maybe I should gather some data say, classifing programms into catagories that would have otherwise been a niche, and see if there is a correlation between closeness of structure, and improvement of the children.

Does this make any sence? If we have multipule populations, we have a smaller chance that the GP will find a relative min/max... If one solution ''gets stuck'', the others can continue improving... I do see your point though...

Good stuff...

Dwiel

When using speciation, a population of genomes is divided into species each generation. When a new innovation occurs (through mutation or recombination) that is far enough apart from any existing species a new species is created.

Typically, a species is killed when either its size decreases to zero or its fitness hasn’t increased within a user defined number of generations. This means the individuals that would normally have died out early in the evolution of a population remain active for much longer, protected amongst their species members. (Note, because of the protection afforded by using speciation you can experiment with much higher mutation rates than normal.)


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