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Subject: Re: Solving small chess

Author: Bruce Moreland

Date: 13:16:34 10/10/00

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On October 10, 2000 at 10:52:54, Pekka Karjalainen wrote:

>
>  Hi folks,
>
>  there were some postings some time ago by Bruce Moreland, I believe, about
>tablebases for chess on the 6x6 board.  That seemed quite interesting actually
>and I started to wonder:  Could we solve 6x6 chess?  If not, how about an even
>smaller variant?

I don't believe that we can solve 6 x 6 chess via retrograde analysis, since
powers of 36 are not shockingly better than powers of 64.

I built a 6-man table and it was well under a gigabyte, but if you try to add a
seventh you are doing multiple gigabytes again, and there are 24 pieces on a
full board.

In case anyone has a burning desire to know, there aren't any huge long wins in
KRR vs KRN on a 6 x 6 board.  This s contrasted with 8 x 8 chess, where there is
some godawful huge conversion case.  It seems intuitively obvious that a knight
is stronger on a 6 x 6 board than it is on an 8 x 8 board, and perhaps this is
enough to draw if there isn't a way for either side to win immediately.

You must be right that it would be possible to solve chess on a board that's
small enough.  I haven't tried to figure out what that size would be.  It might
be practically impossible to do it for any interesting case.

bruce

>
>  You can find several actual small chessvariants from this URL:
>http://www.chessvariants.com .  Basically you can make them up yourself by
>taking a smaller board (any size from 3x1 upwards is possible).  Just set the
>starting position as you please and call it <foo>chess.  The smallest ones are
>obviously trivial and can be solved even on the back of an envelope. You might
>want to remove the castling rule and double pawn moves, and even treat stalemate
>as a win to avoid total drawishness.
>
>  But this is not what I am after really.  I was thinking that would it be
>interesting to try to solve these?  Could we get a program that would search all
>the way from a starting position to its (smaller NB) tablebases?
>
>  One might even get a little feeling about the actual (and huge) computing
>resources that would be needed to solve standard chess.  If 5x5 takes this much
>effort and 6x6 takes that much then 8x8 takes SO much (exponentially more of
>course).  What would a solution to a 5x5 chess variant really look like?
>
>  As I am not much of a chess programmer I do not want to take on this challenge
>myself.  But if it interests anyone at all, maybe it was worth mentioning.
>
>  Comments?
>
>  Pekka K.



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