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Subject: Re: An idea: Offensive and defensive mobility

Author: Slater Wold

Date: 08:40:38 02/06/04

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On February 06, 2004 at 10:49:11, Tord Romstad wrote:

>The ongoing discussion about mobility evaluation has given me a new idea
>which could perhaps be of interest to some:
>
>One of the many difficult problems in mobility evaluation is to decide, for
>each square a piece can move to without getting captured, how big a bonus one
>should give for being able to move there.  One of the main criterions I use
>is whether the piece would contribute to the attack of the enemy king or the
>defense of the friendly king from the square.  This helps my engine to
>notice attacking potential some time before the attack materializes on the
>board.  I also give an extra mobility bonus for pieces which have the potential
>to do more than one task, for instance if the piece can move to squares where
>it attacks the enemy king *and* to squares where it defends the friendly king.
>
>My new idea is this:  Why not compute two different mobility scores for each
>side?  It seems more flexible to compute a separate "offensive mobility" and
>"defensive mobility" for every piece.  One could then use other components
>of the eval to decide upon the weightings for offensive vs. defensive mobility
>for each side.
>
>Has anybody tried something like this before?  How well does it work?

I think just doing a space calculation would be just as good, IMO.

The 4 center squares, and all square around the king being worth more than all
the others.

The side which holds the king (queen or king side) gets a +.  For instance, say
the black king is castled on g8.  White has a queen and a knight on fx & hx, the
queen would be worth 950, and the knight worth 325.  This would also prevent
unsound trades, when your pieces position obviously give you a bonus.)

We had a discussion about planning the other day, and I have come to the
conclusion that a chess engine simply cannot plan effectively, on its own.  So I
am doing the above right now, to try to 'guide' its plans in a more effective
way.



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