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Subject: Re: Evaluation function question

Author: Gian-Carlo Pascutto

Date: 00:23:49 06/18/02

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On June 17, 2002 at 20:01:39, Russell Reagan wrote:

>Secondly, do you think either approach is superior to the other? I think the
>"natural" method would seem to be better. For example, if you reach an endgame
>and castling still happened to be legal, and your program castles to get rid of
>the "non-castling" penalty, even though your king should be trying to get
>centrally located in the middle of the board. If your program had "king safety"
>factors instead of the castling work around, then it wouldn't castle and would
>play a more correct move. Seems pretty straight forward to me, but I've been
>wrong before.

I agree here, in that I tend to make the evaluation as 'natural' as
possible. I do have exceptions though. i.e. my kingsafety consists
of the generic code, followed by some hard-coded exception patterns.

It might be possible to write a better generic function, but the
current method works, and was easier to program.

>Other examples could be using a piece-square table with low values for the
>border squares and high values for the central squares so that the program
>"controls the center" in the opening.

Hmm, I consider centralizing the pieces to be a 'natural' rule.

>Or penalizing pieces that haven't moved
>yet in the opening, or penalizing pieces that have moved more than once, etc.

I do this as well. It would be better if the program avoided this via more
general rules though. In fact, I need to test whether they are still needed.

My program doesn't really excel at understanding board control, so probably
it does.

>These seem to be very poor methods of approaching an evaluation function at
>first thought, but I haven't worked extensively on my own yet, so I'm no expert
>here.
>
>I'd like to know your thoughts...

I very much dislike any kind of assymetric evaluation for the same reasons.
Also things like fixed game stages. Not to mention preprocessing! Urgh!

--
GCP



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