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Subject: Re: Static evaluation after the "Positional/Real Sacrifice"

Author: Peter McKenzie

Date: 10:30:28 12/03/99

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On December 03, 1999 at 08:49:19, Andrew Williams wrote:

>Over the last few days, I have been fascinated by the discussions on CCC
>about positional sacrifices. Some of the discussion has centred on the value

Yes, its been a cool discussion.  Almost an information overload :-)

>assigned to the attack that is obtained after the sacrifice and I was wondering
>how other programs evaluated the position after Hossa's sac:
>
>r3q1k1/ppp1rp2/2n1b2Q/8/2P5/3B4/PPP2RPP/5RK1 b - - 0 2
>
>This is after 1. Bxh6 gxh6 2. Qxh6 from the original position posted by
>Peter McKenzie. PostModernist's static evaluation of the position is presented
>below. Essentially, it thinks that White is winning by 0.71. The ATTACKTOTAL

Lambchop thinks white is winning by 0.22.

>score is generated by analyzing the squares around the King to see how many of
>them are attacked and what sorts of pieces are attacking them. Please note that
>not all the factors that contribute to PM's score are included in the output
>below.
>
>Could other programmers post similar information? I believe that even an
>overall static evaluation would be interesting.
>
>Cheers
>
>Andrew Williams
>
>
>
>SCORE ANALYSIS
>BLACK to move
>
>MATERIAL -137 (Positive means WHITE has more material) W:19086 B:19223
>Game stage M
>Actual moves played: 1 (halfMoves=1)
>
>Fifty move counter: 0
>
>r=547      #       #       #    q=1040     #    k=15939    #
>
>o=103   o=106   o=103      #    r=565   o=94       #       #
>
>   #       #    n=346      #    b=346      #       #    Q=1022
>
>   #       #       #       #       #       #       #       #
>
>   #       #    P=101      #       #       #       #       #
>
>   #       #       #    B=344      #       #       #       #
>
>P=103   P=103   P=98       #       #    R=553   P=103   P=115
>
>   #       #       #       #       #    R=555   K=15993    #
>
>
>HCW=1   HCB=1
>cannotCW=1      cannotCB=1
>CCRW=0  CCRB=0
>
>Piece Bonuses White=4   Piece Bonuses Black=-34
>
>KINGEXPOSURE WHITE=3    KINGEXPOSURE BLACK=16
>DANGERSQUARES WHITE=0   DANGERSQUARES BLACK=5
>ATTACKINGFORCE WHITE=21 ATTACKINGFORCE BLACK=0
>ATTACKTOTAL WHITE=240   ATTACKTOTAL BLACK=0
>
>
>EVALUATION : 71 (positive means WHITE is winning)

Static evaluation: 0.22
King Safety score: 1.1, I don't have a further breakdown of it.
Alot of my king safety bonus is based on attacking squares around the enemy
king.

I suspect I'm not scoring the 'bare' black king highly enough.
Currently I'm only penalising the absense of the g pawn.  I think I should
increase this penalty because there is no h pawn as well.  I'd like a more
generic pattern for a bare king, but haven't decided upon it yet.

Perhaps just a count of the number of friendly pieces around the king would be
good.  By 'around' the king, I was thinking of the 3 squares directly in front,
and also probably the 3 squares in front of those.  In this position, there is
only 1 such friendly piece which is clearly pretty bad.  2 friendly pieces isn't
very good either but 3 seems ok.

cheers,
Peter



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