Author: Andrew Wagner
Date: 20:20:15 02/23/04
Go up one level in this thread
On February 23, 2004 at 23:05:58, Robert Hyatt wrote: >On February 23, 2004 at 18:52:36, Geoff Westwood wrote: > >>Hi >> >>I was perusing the latest table of results, Crafty's static eval of 2 of the >>passed pawn positions were interesting. >> >>Assuming I havent made a mistake in the cutting and pasting >> >>Position 1 >>8/4k3/8/7P/1P6/3p4/4p3/4K3 b - -; id "PP-00004" >> >>[D]8/4k3/8/7P/1P6/3p4/4p3/4K3 b - - >> >>Crafty reckons this is +4.8 (good for white). This is rather clever as although >>the black king could catch either of the white passed pawns, it cannot stop >>both. Also blacks 2 advanced pawns cant do anything as the white king gobbles >>them up easily. Only Crafty and Tinker understand this position statically. Any >>tips on what the algorithm is to sort this one out ? > > >This is the idea I have reported here before, pointed out (demanded to be fixed >in fact) by a GM friend of mine. The idea is that the two separated pawns are >better than the two connected passers. The king stops the two connected passers >easily until the enemy king supports them, meanwhile the split passers walk on >in... > > >> >> >>Position 2 >>8/P5p1/4P3/8/2k5/2P1pb2/8/4K3 b - -; id "PP-00005" >> >>[D]8/P5p1/4P3/8/2k5/2P1pb2/8/4K3 b - - >> >>Crafty reckons that this is -7.16 (won for black ??) > >This one it just gets wrong. It is fixable as the pawns are so advanced that >one promotes, decoys the bishop, then the other promotes. At present, the >search has to resolve this but it only takes a couple of plies..... > >> >>Firstly is this a typo should it be +7.16 ? Surely this position is won for >>white as the bishop cannot stop both pawns again. >>If not a typo Crafty seems to be statically evaluating this quite badly, maybe >>the clever eval in the previous position is flawed ? Or I have got my +/- signs >>confused. > >The previous one it gets right, this one it just misses, but the miss is a >result of the pieces. Take the pieces off and it gets it right most of the >time, as it should. > > > > Am I understanding correctly that you use a completely different eval function in pure king/pawn endgames? E.g., surely in the first example, with a bunch of pieces on the board, the connected passed pawns would be better, because the pieces can catch the separate passed pawns whereas the connected once can defend and advance themselves. >> >> regards Geoff
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