Computer Chess Club Archives




Subject: Re: likelihood instead of pawnunits? + chess knowledge

Author: Sune Fischer

Date: 10:15:03 10/25/02

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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
>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).

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.

>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

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).


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