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Subject: Re: Secrets of Rybka and Fruit from my point of view

Author: Daniel Shawul

Date: 04:59:22 12/16/05

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On December 15, 2005 at 17:05:00, Sergei S. Markoff wrote:

>1) Fruit.
>Fruit search seems to be primitive. "History pruning" is a variation of
>well-known idea. After implementing such method in SmarThink some years ago I
>named it "history-based pruning" and then changed to "ordering-based pruning".
>The outcome of such methods very depends of whole search model, but anyway
>history pruning is not the key to Fruit strength.
>To my mind, the key of Fruit strength is that the "Chess is the art of
>exchange". So, Fabien's idea about flexible game stages looks to be a beautiful
>way to improve positional play. Fruit can effectively consolidate the position.
>It simply knows when to excange to improve position. I think that it's the main
>key (cumulative with very good tuning of evaluation function). I think Fruit is
>very perspective. The main line of progress for this project, to my mind, is to
>add more complicated knowledge and intellectualize a search.
   I think it is impossible to make a smooth transition from phase to phase in
all cases. For example, most evaluations change very much after a queen
exchange. Most engines evaluate king safety very less if not 0 after a queen
exchange. How can you avoid this?
I agree that having a separate evaluation for different phases of the game is
important but it is impossible to make a smooth transition in all cases.

My guess: history pruning (relatively safe huge depth) + tuned evaluation

>2) Rybka
>Some time ago we discussed with Gian-Carlo Pascutto an idea of create special
>"SET-tables" with sets of piece-square values indexed by 1) material on the
>board; 2) king position; 3) pawn structure. Such tables can be calculated by
>analyzing a lot of games. That time I delayed my work in this area because I
>found other perspective things.
>You can see that Rybka executable contains a lot of precalculated tables. And
>also we all know that Rybka plays positional style. My version is that Rybka
>uses some variation of SET-approach. At all cases it uses some precalculated
>positional knowledge, but what sort of it? ;)

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