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Subject: Re: Static Eval Test

Author: martin fierz

Date: 12:41:50 09/08/02

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On September 07, 2002 at 19:46:49, Peter McKenzie wrote:

>I've been having a break from computer chess post WCCC, but have now started
>going over some of Warp's games.  First up is Warp's worst game, the loss vs
>Brutus.  In this game, Warp showed a total lack of understanding of its
>centralised king in the early middlegame and lost without a fight.
>
>I present here the position after move 21 in the game.  White has grabbed a pawn
>thinking this position is OK, but in reality the white king is hopelessly stuck
>in the centre.  Also, white is passive, black is active and has a safe king,
>therefore white is totally winning here:
>
>[D]r1r3k1/1p3ppp/b5q1/p7/4n3/P3PNB1/1P3PPP/1Q1RK2R b K - 0 1
>
>I am curious what the static evaluation of various programs is here.  The
>version of warp used in Maastricht gives 0.238 in favour of white.  Ideally the
>static evaluation should favour black here I think.
>
>cheers,
>Peter

the only important thing to recognize is that

Ba6 prevents castling && lots of material (queens!) on board.

i think you can easily give this kind of feature a value of 1 pawn.
however, you have to be kind of certain that it is here to stay. which
means that you should make sure that there is no move like c2-c4 before
applying this kind of rule. gerd gave a nice description of what his eval
is doing here, but i think part of it is no good: his count of "There are four
black pieces controlling squares with distance two from king." is probably no
useful measure. e.g. place the black bishop on b6 instead of a6, and you still
have that feature, but now it is black who has to hope for a draw.

i know what you are worried about when not giving the "Ba6-prevents-castling &
queens on board" feature a higher eval. it might go away again, if white could
play something like Be2 or Ne2 and then castle. i have often thought about
similar things in my checkers program. in the end, i usually put high eval terms
for this kind of feature in anyway, because i think that if white can free
himself from this type of bind, the search will find it. however, if he cannot,
then it is very important that the eval tells you that he is in trouble. of
course i can search much deeper in checkers, which helps me believe that the
search will find it...

aloha
  martin



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