Computer Chess Club Archives




Subject: The superior Rybka chess knowledge

Author: Chrilly Donninger

Date: 10:34:17 01/18/06

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.

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