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Subject: Re: Assymetry & Bonus in Static Eval? Black apples and white pears?

Author: Eelco de Groot

Date: 19:09:41 12/04/99

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Do I understand correctly--for each static evaluation of a single position (leaf
node, I guess), the program evaluates based on material and positional factors
without regard to which side is on the move?  Then, some programmers like to add
a bonus for the side to move?

It's an heuristic that's true in 99% of the positions that my program
searches obviously.

If a position is bad then usual programs nullmove. If a program nullmoves
then the other side has the move so gets the bonus.

So the sword cuts on 2 sides. Where you can nullmove normally to prevent
getting into a worse position, you now suddenly cannot as your opponent
gets the bonus instead of you.

Now I have never done any chessprogramming, but it seems fairly straightforward
to say that you only need to think about such a bonus if you are comparing
positions with White to move and positions with Black to move, right?
Intuitively something tells me that is not without dangers. Isn't that a lot
like comparing apples and pears? Wouldn't it be a lot better if only even plies
were evaluated if possible? A recent discussion between Ed and Christophe about
the early Rebel comes to mind... That way you can focus much more on plans ,
weaknesses, etc. of your own. You could save a lot of time time that way! Of
course you can't ignore the opponent regardless, but you could use a different
evaluation for uneven plies, looking more for tactical threats for instance?
That would be relatively safe to do as long as you have the initiative..

If this isn't possible because of nullmove, isn't that a weakness of normal
nullmove? Vincent I understand you are working on something you call double
nullmove and that you are going to publish in ICCA journal about it. Has this
anything to do with these even/uneven effects. Has double nullmove replaced the
bonus in Diep? I must confess nullmove is hardly my expertise, but maybe others
can follow better if you have anything to say about this.

Thanks for any comments, by anybody


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