Author: Robert Hyatt
Date: 05:55:06 06/12/01
Go up one level in this thread
On June 12, 2001 at 04:30:48, José Carlos wrote: >On June 11, 2001 at 11:19:55, Robert Hyatt wrote: > >>On June 11, 2001 at 03:05:27, Uri Blass wrote: >> >>>On June 11, 2001 at 01:31:14, Jouni Uski wrote: >>> >>>>[D]8/4k3/2K5/6p1/6B1/7P/8/8 w - - >>>> >>>>I tested this simple draw position with 3 engines: >>>>Fritz5 +4,53 no TBs >>>>Goliath +3,39 no TBs >>>>Crafty18.7 +5,01 with 4 piece TBs >>>> >>>>Hmm. Should this already be solved poblem? >>>> >>>>Jouni >>> >>>The position is not simple draw. >>>I have not the tablebases to find out if it is a draw or not a draw but white >>>may try to force black to play g4 by zunzwang and to win after hxg4. >>> >>>Uri >> >> >>I have looked at this position a bit closer. It is not so easy to statically >>evaluate this one as a draw. Crafty does this early on, but it is possible for >>white to eventually zug black into moving. The problem is that if black really >>gets zugged, the pawn move will lose. Without the black pawn, this is trivially >>drawn, but with it, black has problems staying in front of the pawn. I think >>it is likely that many programs could actually lose this without tablebases. >>But in any case, Crafty discovers that there are problems here that make it >>non-trivial to claim it is drawn: the black king can't get into the corner >>and stick because white will him in and zug him to push the pawn and lose. > > I don't see why the black king can't get to the corner. The only way I see >white can force black to move the pawn is something like this: > >[D]7k/8/4B1K1/6p1/8/7P/8/8 b - - 0 6 > > Here, after ...g4: > > hg4 is stalemate > Bg4 is a draw due to the h pawn and white bishop. > > Of course, this is difficult to statically evaluate. > > José C. That is the problem. You give up the pawn in the q-search, which (in my case) does not recognize stalemate. So you see "I am down a pawn, in a probably lost position (endgame knowledge) so I have to leave the corner instead and let white take it over. Of course, white still isn't going to make progress, but that is another issue.
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