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Subject: Re: Rybka uses PVS and not MTD(f). Its no Fruit-Clone

Author: Vasik Rajlich

Date: 00:27:57 12/13/05

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On December 12, 2005 at 13:29:45, Chrilly Donninger wrote:

>On December 12, 2005 at 13:03:16, Vasik Rajlich wrote:
>>On December 12, 2005 at 07:26:38, Chrilly Donninger wrote:
>>>On December 12, 2005 at 05:19:49, Ryan B. wrote:
>>>>On December 12, 2005 at 04:58:52, Chrilly Donninger wrote:
>>>>>I did not follow the CCC-discussion the last months/years. So please do not
>>>>>"kill" me if I am telling old stuff. I got questions about Rybka from the
>>>>>Hydra-sponsor so I read yesterday evening some of IM Vasik Rajlichs very
>>>>>interesting postings in the archive.
>>>>>Vasik mentions several time MTD(f) and his experience with it. But when playing
>>>>>with Rybka, it looks like a normal PVS-search. I looked therefore also in the
>>>>>Rybka-Code. What I have seen so far is typicall PVS-Code.
>>>>>From this first look I can say that Rybka is not at all a Fruit clone.
>>>>You could look at Fruits source or just read the readme files :)
>>>Well, for Fruit one has to know C. Quite a problem for an old Assembler-Hacker.
>>>But in contrast to Frans Morsch I am in the meantime used to C.
>>>Rybka is somewhat easier. There one can directly read the machine/assembler
>>>code. No retranslation from C to Assembly is necessary :-)
>>>Rybka is obviously written in C. It looks like gcc was used for compiling. The
>>>code is not particullary well optimized. Maybe the Rybka team can buy from the
>>>first royalities a professional one from Intel or Microsoft.
>>Not to mention an encrypter :)
>Yes, that would make the challenge more interesting. But not only dissassembling
> of fishy is fun. Rybka has a complete different style to Shredder et al. There
>was/is a trend what I call "Hyperdynamism". The programers want to simulate
>Kasparov or in case of Hydra, Tal. E.g. in the game Ponomariov-Fritz, Bilbao
>2005, Fritz sacrificed for minor compensation the b7-pawn. Rybka is in contrast
>a "neo-classical" progamm. The Karpov of computer-chess. Sound play, no own
>weaknesses. It does not care too much about the space advantage of the opponent.
>And if this dynamic factors are just thin air, it has structural advantages like
>better pawn structure or the bishop-pair. The hyperdynamic programs are eagerly
>willing to accept these - from their point - minor drawbacks for a dynamic
>Computer Chess and especially programming has become more interesting due to
>Rybka and to Zappa.

Interesting observations. I can a few comments:

1) I don't really like the term "pawn structure" and would replace it with
something like "pawn placement". As a rule of thumb - if you can store it in the
pawn hash table, it's not very useful :)

2) Rybka is probably going to evolve. Shredder, Junior and Fritz all evolved in
the direction of being more dynamic as you put it. Zappa, Rybka and Fruit are
all much younger. You could say that this hyper-dynamism is a sort of acquired
taste in computer chess.


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