Author: Fernando Villegas
Date: 17:37:58 05/21/98
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On May 21, 1998 at 20:11:57, Don Dailey wrote: Hi Don: Your experiment is incredible interesting. You are following the paths of nature that were forbiden to us because lack of resources and time, but now technology is providing us with the means to imitate the vast use of number through which evolution happens. In fact, what you are doing is an step further the way computer give us in order to use simple but efective brute force approach where sheer intelligence could do not too much. Instead of trying to forecats the better evolutionary line in any kind of enterprise, we can just simulate now what happens if all variantions are putted toguether to compete. I am sure you see this approach go far beyond the creation of a better chess program. There are in this enterprise so wide and deep implications that I almost feel some panick. Just think in what could happen or just has happened in that kind of secret laboratories of the great powers. fernando >> Could you describe your methods and results to me? I'm very interested! > >Hi Stan, > >I'm going to post this email because it might get others interested in >GA's too. But I'll also send it via email. > >Essentially, I set up about 100 "individuals" with random weights for >a few of the evaluation terms. I gave each guy a fitness number which >essentially was an elo rating. I started the first group exactly the >same for everyone. > >I did not proceed by going from 1 generation to a completely new >generation. Instead, I just played games pretty much selected at >random. I tried to choose the opponents based on how many games they >had played so that new individuals would be more likely to play than >ones who had played more. The openings were selected at random from >among 200 possbile opening positions and so was the color. After each >game I would rate them incrementally using a simple linear version of >the elo chess rating formula. I used 4 percent of the rating >difference as a handicap and 16 points to the winner. Handicap was >limited to 16 points. > >After every n games, (I think I used approximately 50 games here) I >would select 2 fit parents and produce a child. The child would >replace an UNFIT member of the population. I used a method I call >"best of n" to make these selections. Here is how it works: > >To determine parent A, pick 3 candidates completely at random. Then >choose the highest rated one as parent A. Do the same for parent B. >A similar procedure determines which member of the general population >to "kill" off to make room for baby (worst of 3.) > >Here is how the "mating" process works. For each term, I would choose >randomly whether to select it from parent A or parent B. Occasionally >I allowed a "mutation" which was simply picking 1 or 2 terms and >making a random adjustment to it. The adjustment was not unusually >large or small, but I thought it made more sense than just changing it >to a completely random value. I don't have any reason other than my >own superstitions for believing this though. > >Some other details. The pawns were fixed at 100 points as a reference >point. I limited the range of possible adjustments/values to >something like 2000 points for any piece. "Babies" inherited a rating >which was the average of their parents rating. I figured that since >their parents were likely to be fit, this would give them time to >establish a rating and not get killed off too soon. Of course >sometimes they would prove to be fitter than both parents and other >times they would be less fit than either parent. > >I thought this model was reasonable. Each "guy" was fighting for his >life, your rating gets too low and suddenly you're in danger of >getting deleted! If you do well you are rewarded with the right to >have children! Now that's a lot of pressure to have to endure! > >I am sorry to report that I do not have a record of the results. It >was pretty encouraging though and I had eventually planned to follow >up on it. But from memory I can tell you that the values of the >pieces converged to very reasonable values. I remember that they were >not quite the values I would pick, but they were not unreasonable. >It's unclear what would have happened if I had run it long enough. > >It was quite interesting to watch over time. I would observe strong >individuals survive into old age, only to eventually weaken and get >replaced by the stronger and smarter younger generations who were >decendants. After a while I almost mourned their deaths! I kept >around members of the original group, preserved in ice, so that later >I could thaw them out and let them have it out with the new guys. The >difference in strength was enormous. > >The real problem as I see it is that there is a lot of imprecision in >the actual fitness function. Any given individual can get seriously >underrated or overrated by having a little bad or good luck. Even >though the selection process itself is a litte random and murky, I >believe the fitness function itself should be solid and in this case >it was really very very fuzzy. Measuring small differences is almost >impossible. > >To be really robust, I believe a hierarchy might work well. You breed >small groups independently, let the best individuals move out of these >small towns to compete with the big boys (who themselves came from >small towns.) In this way, you will create individuals who have what >it takes to beat a wide variety of opponents. Also you would be >constantly refreshing the gene pool. > >- Don
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