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Subject: Re: not using nullmove?

Author: Tord Romstad

Date: 08:09:29 02/16/04

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On February 16, 2004 at 10:24:26, martin fierz wrote:

>On February 16, 2004 at 09:46:24, Tord Romstad wrote:
>>
>>Thanks.  I am painfully aware of this one, and I have seen lots of lost
>>games because of this hole.  My latest development version is slightly
>>improved in this respect, but there is still a long way to go.
>
>here's an easy way out: make the connected passer eval larger for pawns on c6/d6
>larger than for pawns on c6/d7 or c7/d6. like that, you will only push the pawns
>if you see them either getting to c7/d7 or promoting. else you'll rather keep
>them on c6/d6 - in general, they are better beside each other than diagonally
>aligned.
>i currently try detecting whether they're blocked when diagonally aligned, but i
>guess the above should work even better.

I have something like this in mind, as well.  Something like this could
be useful even elsewhere on the board, and not only for connected passed
pawns.  Pawns side by side are usually stronger than one pawn defending
another, aren't they?

>>Other major weaknesses are that lots of important endgame knowledge
>>is completely missing,
>
>i think i saw KRP-KR once, muse on the weak side, clear draw. gothmog thought it
>was about 1.5 pawns ahead IIRC. a simple but good rule for this one is: if the
>king of the defending side is anywhere on the pawn's path to a queen, it's a
>draw - i don't return a draw there, but something like -0.5 pawns for the
>defender - after all, you still have small chances against a weak opponent. but
>perhaps this was in a game against frenzee - i hope i haven't mixed things up...

This sounds entirely correct, but it is fixed in the latest development
version.  I have written a special KRPKR eval which knows about most of
the basic winning and drawing positions (including the third-rank defence),
as well as the basic principles of the endgame (like keeping the rook
on the long side and the king on the short side).  It seems to work
pretty well, except that I still have to do some tuning to make it all
consistent with the eval for more complicated endings.

>> that the space eval is too big and too primitive,
>>and that Gothmog is too happy to push pawns in front of its own king in
>>positions with opposite side castling.
>
>i haven't noticed that too much yet. you should of course push the pawns on the
>other wing :-)

Yes.  The problem is that my stupid engine sometimes thinks it can slow
down the opponent's pawn storm by advancing its own pawns.  For instance,
when Gothmog has castled queenside, it frequently plays the move a2-a3,
because it thinks this will make it more difficult for black to advance
the b pawn.  Usually, this doesn't quite have the desired effect.  :-)

Tord



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