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Subject: Re: The superior Rybka chess knowledge

Author: Vincent Diepeveen

Date: 13:14:31 01/20/06

Go up one level in this thread

On January 19, 2006 at 08:10:34, Vasik Rajlich wrote:

>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.

Fischer played very classical openings, Rybka on other hand is good in modern

Fischer took big risks on kingside sometimes, Rybka never takes risks there.

In that sense, Rybka is a very ugly player from human viewpoint are.

Of course Rybka is not unique there. Most engines qualify there :)

I remember Fernando comparing it with Karpov. However Karpov is a very
positional player, and Rybka isn't. There is a dozen engines more positional as
they have more knowledge (which of course means you could have potentially more
bugs, i agree in that respect with Chrilly, but it also means they have more
potential to play strong in future if those bugs ever get fixed). Shredder is
100x closer to Karpov than Rybka is.

Rybka compares well with the Richard Lang style programs from a decade ago, in
term of style.

What we do know already for many years is that tournaments in computerchess are
won easier by passive bugfree play, than by agressive attacking play.

Shredder and Genius are good examples there. Fritz3 in its glory days was very
passive too.

It is a race against bugs in computerchess always, in that sense you're doing a
superb job currently with Rybka. Very bugfree play.

>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.

Odds are of course zero that we'll ever meet Nimzo1998-on-stereoids or Fritz in
an official tournament ever again. Well that is, unless someone manufacturers
some real fast 'pocket pc' in which case Pocket-Fritz version 10.0 might win.
But hey, we might also know that under a different name... Shredder 10.

However i do appreciate the fact that one author is saying the truth about the
other author.

Any claim of having a lot of knowledge in rybka, which for the average person
suggests it has more than others, must be proven of course and the obvious proof
which everyone can see in your assembly code is that it has real little. So it
was a clear lie. The "advocate of the devil" type of explaining things is not

A claim can be very valid from juridical viewpoint but very wrong from social

Chrilly clearly pointed that out for which we have to thank him.

Please in future remember the big difference between lying, juridical non-lying
and marketing claims. There is a big difference between the two. A good
dissassembly specialist like Chrilly, his findings there are very valid.

Perhaps take over some marketing slogan from Chessbase a few years ago:
  "Rybka learns through search".

Nothing wrong with that.

By the way, it wouldn't hurt to show what you do in search, all the top 20
programmers gonna debug it anyway in your program, the top 2000 however which is
in this forum who can't read assembly as well as Chrilly nor Frans, they like to
know :)


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