Author: Dieter Buerssner
Date: 08:48:07 11/22/04
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On November 22, 2004 at 08:56:43, Heiner Marxen wrote: >On November 22, 2004 at 05:49:05, Laurens Winkelhagen wrote: > >>Because there is a difference between the white and black side, it makes a >>difference which side mates. The above score tells us that the biggest maxDTM is >>when the white (KRP) is to move and to win. >> wtw btw >>wtm 166 103 >>btm 153 104 >> >>It seems logical that if black (KBP) is to win, then the mate should be shorter, >>because one may not give white a chance to take the pawn with the rook. >>Obviously this is easier when the pawn is closer to promotion. >> >>One puzzling thing left is that it makes a big difference for white to mate if >>black is to move or white is. One would expect only a difference of 1, not of >>13. It probably has something to do with going over into a different tablebase? > >I would think, that positions, where wtm/wtw has a large DTM, it is so hard >to win, that loosing the right to move, also gives up the wtw property. >So, for large DTM changing wtm/wtw to btm does not yield a btm/wtw position. I think Laurens is right. There is one position, where white (=RP side) has the right to move, and announces mate in 166. Now he moves. Assume it is neither a capture nor a promotion. So still KRPKBP and btm, value of the pos: mated in 165. But this is not in the table above (or in the values given by Guy). So we should be able to conclude: the first move must either be promotion or capture. I can easily check the capture thesis: KRPKB btm: Max is lost in 73; KRPKP btm: Max is lost in 66. I don't have the values of promotion tables, but from common sense it looks strange. If white promotes (probably to queen), and black doesn't very soon, it should be a much faster mate - not? If black does promote too rather soon, we have KQRKQB. Here longest black loss is in 89. So, what is the first move? Perhaps I am missing something obvious ... Regards, Dieter
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