Author: Marc Bourzutschky
Date: 09:59:29 11/22/04
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On November 22, 2004 at 11:48:07, Dieter Buerssner wrote: >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 Hint: underpromotions!
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