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Subject: Re: The superior Rybka chess knowledge

Author: Vasik Rajlich

Date: 05:10:34 01/19/06

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On January 18, 2006 at 13:34:17, Chrilly Donninger wrote:

>After playing several engine matches against Rybka (chess programming is a
>rather boring job) I have come to the conclusion: There are a few special
>evaluation features of Rybka which are really unique. It is interesting that
>some seamingly relative unimportant feature appear regularily on the board. The
>opponent has no idea of this feature and does not prevent it. And the search
>always finds a way to reach the pattern. Rybka has e.g. some special passed pawn
>evaluation terms. I do not want to tell the details, but the game Zappa-Rybka,
>Paderborn 2005 is a prototype game for one of these special features.
>But the main chess-knowledge which sets Rybka appart from other engines is
>ignorance. The omission of features which other engines have incorporated.
>I have written a longer article for the German "Schachkalender 2006". The
>message of this article is: Most of the published chess knowledge is completly
>useless. Give your favorite chess-enemy your chess-books as a present. They will
>do some harm on his play.
>Rybka seems to be to prove of this hypothesis. If a feature is - in a given
>position - correct, it is of course an advantage if a programm has implemented
>it. But if its wrong, the programm hangs on an advantage which does no really
>not exist. Or even worse, it sacrificies another advantage to reach the pattern.
>I realized the principle: "It is sometimes more important to remove features
>than to add ones" several times in the Hydra project. E.g. Piece-Square Tables
>are generally considered as a "must have". Strong Chessplayers do not like them.
>It is very unnatural for them to evaluate a piece without considering the
>context of the other pieces. It took some time till GM Lutz convinced me to
>remove them in Hydra. And indead, the programm played considerably stronger with
>Insofar is the Rybka approach intelligent ignorance.
>P.S.: The omission of Piece-Square-Tables is a feature of Hydra. I do not state,
>that Rybka as skipped this feature too.

Yes, what you omit is just as important of course.

A game like Zappa-Rybka would be much more likely to be played as black by
someone like Fischer than someone like Tal. It's not because Tal doesn't know
the basics about a queenside pawn majority.

I suspect Hydra will have a harder time than Rybka playing a position like this,
but then again Rybka will have a harder time in some other types of positions.
Fortunately in chess we have a way to settle these things.


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