Author: James Swafford
Date: 11:17:49 10/25/02
Go up one level in this thread
On October 25, 2002 at 13:15:03, Sune Fischer wrote: >On October 25, 2002 at 12:39:38, Ingo Lindam wrote: > >>I would really like to see the computers measure a position rather in a >>set of probabilities e.g. (P+,P=), where >> >>P+ = Probability in the position to evaluate white/player to move will >>win and >>P= = Probability that position will end in a draw >>P- = Probability in the position to evaluate white/player to move will >>lose >> >>with P+ + P= + P- = 1 >> >>(also a confidation measure about the Probabilities might be useful) > >The pawn scale is equivalent so it doesn't matter, you can see the mapping in >eg. the article on TD(lambda) for the KnightCap engine (I think Dann has it on >his ftp). > It is a hyperbolic tangent function, so the probabilities are in the closed interval [-1..1]. So small changes in the "pawn units" evaluation yield a more dramatic shift in the probablility if the score is drawish (vice if you're already losing or winning by a queen). >I prefer the pawn scale since that is in integers, also the mate scores are >easier to work with I think. >One could print out the score in probability terms, but there is no tradition >for that either in human chess or computer chess. I agree, but only because I'm so used to looking at the pawn scale that I tend to try to "reverse map" a probability back to the pawn scale. > >>Ofcourse out of the set of probabilities a single measure could obtained >>to be optimization criteria in an search algorithm. A simple one would >>be P+ + 1/2P=, but also different formulas considering strength of >>opponent, standing of the match or just an increasing influence of P= >>when position is weak might be interesting. >> >>Even more important seems to me to demysticize terms like "chess >>knowledge", "experience", "plans", "positional criteria". >> >>There is such a huge amount of chess games and analysis in a computer >>readable/usable format and what else should be a source of chess >>knowledge than games and results? Yes, there are books and ideas of >>great human chess thinkers as Nimzowitsch. But also his ideas are >>experiences from his own analysis and games and should also be >>verifyable by modern pratical chess. And where not, they might be no >>longer of any use. >> >>A chess engine that is able to calculate 3 Million positions per second >>should have no problems with dealing with less than 2 Million. As more >>as a lot of conclusions out of the "experience" of 2 Million chess games >>may be drawn rather in preperation of a match than during a game. >> >>"Positional pattern" (another mysticized term reserved for human beings >>especially GMs) may easily formulated and efficiently retrieved on the >>basis of low level chess position items and clusters of those. Computer >>scientists may argue that there is a too huge amount of possible >>patterns. But a chess engine as well as a GM (not less a normal human >>chess player) should first of all be interested in patterns that often >>apear in practical chess. >> >>I expect that a CD (or DVD) full of positional chess patterns drawn out >>of a suitable number and choice of chess games (out of a permanently >>growing number) will have a much greater effect on the play and results >>of a chess knowledge using chess engine than 4 or 5 pieces tablebases >>have nowadays on the results of tablebases using chess engines. > >Patterns are used in chessprograms, connected passed pawns or rook on open file >for instance. Consider that computers are too small and slow to be using a >neural net with 100 billion neurons for the entire postion like humans. Besides >how would you train it? You need scores on every position, which you do not >have. Agreed about the size of the neural net, though that may not be true forever. I think you should be able to derive a score from game outcomes. > >For "probing" a CD you first need to design some clever index scheme and if you >plan to use it at every node it's going to slow your program to a crawl (of >course that wouldn't matter much if it was extremely accurate). True, but ... :) computer scientists are often not interested in hardware limitations. Instead they concern themselves with what is theoretically possible. > >-S.
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