Author: Tim Foden
Date: 05:33:11 02/11/01
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On February 11, 2001 at 00:29:23, Uri Blass wrote: >On February 10, 2001 at 16:26:39, Pete Galati wrote: > >>This is another position that crashes Crafty, so I assume that the Chessbase >>interfaces probably won't like it either. > >The chessbase interface have different rules then crafty. > >It does not like positions when >max(number of white bishops-2,0)+max(number of white knights-2,0)+max(number of >white rooks-2,0)+max(number of white queens-1,0)+number of white pawns>8 > >It also does not like cases when it is truth for black and does not like >positions with more or less than one king for one of the sides >It does not like positions when the side to move threats check >or positions when there are pawns in the 1st or 8th rank. > >There is no problem with other positions including this position that is >illegal: > >[D]B1Bk4/1B6/B1B5/3B4/4B3/5B2/6B1/4K2B w - - 0 1 > >It is interesting to know how much time do your program need to see the draw(if >your program does not accept the position then you may remove one bishop from >the board). I think most (if not all) programs will have a very hard time solving this position. GreenLight did the same as Crafty in Pete's reply, but I was not at all surprised. >Can chest prove that there is no mate when the number of moves is not important? I don't think so, but I'm not sure. >I have no problem to prove it. >Uri I agree. Neither do I. So the questions are: 1. What exactly do we do when we solve it? 2. How can we get a computer to do the same? In answer to (1.), my proof was: In order to checkmate a king, you must be able to check him. Only the bishops can check the black king. The bishops are all on the white squares, so the king can always avoid check by not moving onto any white square, or be stalemated. Therefore the position is draw. There are also other ways to prove this I think. e.g. You could prove that if the king is in check, he will always be able to get out of it. For (2.) though, I haven't a clue! (Yet ;-) I think this is an interesting area really, as I have been giving thought to quite a few of these - easy for humans/hard for computers - positions. Cheers, Tim.
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