Computer Chess Club Archives




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

Author: Chrilly Donninger

Date: 22:28:19 12/15/05

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On December 15, 2005 at 21:55:02, Robert Hyatt wrote:

>On December 15, 2005 at 21:14:45, Sergei S. Markoff wrote:
>>>>>I find that VERY hard to believe. That concept has been around a
>>>>>very long-time.
>>>>Really? Where it was introduced by the first time?
>>>Don't know about the first time, but GNUChess (v4) uses the same approach,
>>>albeit only for some king eval terms, and many programs scale things by
>>>material, although not necessarily as nicely as Fruit does.
>>Well, I think such material dependence for some factors was in Kaissa too :) But
>>I never seen before Fruit the united concept of opening/endgame evaluation. Also
>>material dependence of some factors seems to be appeared at first time in Fruit.
>>For example -- piece mobility depends of stage.
>That's not new at all.  I can think of several programs that have done this
>"scaled" eval approach since the late 1970's...  If you look at Crafty's eval,
>you will see it done much more subtly than what is done in Fruit.  Individual
>eval terms are scaled by material when appropriate.  Endgame things like passed
>pawns, distant passed pawns, pawn majorities/candidate passers, all scale up as
>material comes off.  King safety scales down in the same way.

I scale the terms also individually. I think most programms do that. But the
Fruit approach has some beauty. With the individual approach one has more
freedom for tuning. The relation between material and the eval terms differ. But
one can also introduce inconsistencies in the eval. Its hard to keep everything
balanced. The formula is typically for Fruits KISS approach. Its hard to do any
stupid things with the Fruit-formula.



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