Author: Uri Blass
Date: 11:25:22 11/17/04
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On November 17, 2004 at 13:32:44, Robert Hyatt wrote: >On November 17, 2004 at 09:31:53, Alessandro Scotti wrote: > >>On November 17, 2004 at 08:27:47, Jan K. wrote: >> >>>Under winboard/arena which of the following positions should be claimed(/can be >>>claimed) as drawn by insufficient material-KBKN, KBKNN, KNNKNN? I thought that >>>KBKN can be claimed as a draw, but once this position happened under Fritz GUI, >>>my engine claimed draw and stopped playing but GUI still expected me to move and >>>my engine lost on time. Thx. >> >>According to FIDE rules: >> >>"The game is drawn when a position is reached from which a checkmate cannot >>occur by any possible series of legal moves, even with the most unskilled play." >> >>If this is followed strictly, there are not many possibilities! That said... I >>think I also have the KBKN bug! :-) > > >It is easy to construct a position where KB mates KN. It seems to be impossible >to construct a position where that mate position can be forced. Calling it a >draw is perfectly fine IMHO. It seems that mate with the bishop against the knight cannot be forced but mate with the knight against the boshop can be forced(from root position that has more pieces). White cannot prevent that mate in the following diagram so claiming a draw only because the position in the board is KN vs KB is generally wrong. [D]1r6/8/8/8/8/k2B4/p2n4/K6R w - - 0 1 1.Bc2 Rb1+ 2.Rxb1 axb1Q+ 3.Bxb1 Nb3# Note that I see that Crafty has no problem to see the mate in this line so it does not return a draw for KB vs KN and stop to search. If the engines have no bugs it may be logical to adjudicate games of KB vs KN as draw after there is position with KB vs KN when there is no mate in 1 but not to do it only based on the fact that the position is KB vs KN. Uri
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