Author: Sune Fischer
Date: 05:54:49 06/22/02
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On June 22, 2002 at 08:23:01, Stan Arts wrote: >Hello, Hi, What you have described sounds like a horizon problem. Are you doing quiescent search to terminate at a 'quiet' position? Your queen certainly shouldn't plunge into pawns just before an evaluation. Take a look at this tutorial by Bruce Moreland: http://www.seanet.com/~brucemo/topics/topics.htm in particular the quiescent part. -S. >Last time I wrote a question regarding strange behaviour of my simple fixed >depth alpha beta program. Indeed there was a bug in the program causing this >behaviour. Thanks for suggesting this because I had looked over my program >many times thinking there weren´t so I simply experimented a lot until I >located the error. Thanks! It now calculates "perfect" it seems! (=play as >should be expected upto X ply deep) Just like a real chessprogram... :) > >Anyway, now I noticed something else strange to the play of my program. When >it´s searching, on EVEN ply´s (for instance 6, or 8) it seems to play 100% >correct. But on ODD ply´s (like 5 or 7) sometimes it makes mistakes. (In the >calculationtree I count the 1st ply to be the possible moves by the computer, >of which one of these will actually be played after calculation. , so say a >5 ply deep search by my program is 3 moves by the computer, and 2 by the >opponent, and therefore, the deepest ply (5th) is that way a computermove) >Now I looked over the code very often, but can not find an error, but this >morning I suddenly thought of this: When doing a fixed depth search, without >extensions, would these evaluation errors on ODD ply´s come from the fact >that on this 5th ply it would for instance plunge it´s queen into a random >(protected) pawn because on the deepest move, ofcourse it can´t see a >recapture? And therefore mess up the evaluation because it thinks it can get >this material back? It seems to happen just rarely luckly, but I imagine in >some occasions with a queen centrally located for instance and on a shallow >search such as just 5 ply (not much change to the total position), this >material gain would show up in EVERY branch and therefore mess up the >evaluation? > >Would this be right and did anyone have the same problem? because then it´s >not a bug and I would sleep a little better at night... > >:) > >Stan
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