Author: Christophe Theron
Date: 18:25:11 10/01/98
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On October 01, 1998 at 17:54:48, Jim Phillips wrote: >On October 01, 1998 at 08:25:15, Roberto Waldteufel wrote: > >> >>On September 28, 1998 at 11:28:42, Peter Fendrich wrote: >> >(snip) >> >>>Sure, winning games is better than losing them... :) >>>Search does in fact have some good effects by itself... >>>There was an intresesting article in ICCA Journal a few years ago. I don't >>>remember any details about the authors and such but here is what I remember from >>>the article. >>>They played two programs against each other with completely random evaluation. >>>One program searched the tree, gave the leafs a random evaluation and and backed >>>up the values in an alfa/beta manner. The other program just gave each move from >>>the root a random evaluation. The first thoughts about a match like this is that >>>the result will be as random as the evaluation code, but it wasn't! >>>The results showed that the tree version was better because of a tendency to get >>>more space just because of the tree search itself. Well, my memory is fading >>>here... >>> >>>//Peter >> >>Maybe the tree version would find shallow mates, and the root version would not? >>I think this might well account for the difference. >> >>Best wishes, >>Roberto > >I'd like to throw in my 2 cents.... If you choose a move at random from >the "leaf" nodes, you are going to tend to return to a root move that >generates a "bushier branch". Let's say you have three possible root >moves, and you search two plies deep and choose a move at random. If >there are 10 "leaves" corresponding to the 1st root move, 20 leaves >corresponding to the 2nd root move, and 70 leaves for the 3rd root move, >there is a 70% chance that your random function will choose the 3rd root, >which is the one that will also lead you to a more open position with a >lot of possible moves to make. The program that simply chooses a move at >the root at random has only a 33 1/3 % chance of picking the 3rd root.... >Does this seem reasonable, or am I off around Jupiter? >-Jim Phillips You are absolutely right. The random evaluation in fact turned out to be a way to find the moves that lead to more mobility. Both programs were able to find shallow mates. This was not the issue here. Christophe
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