Author: Dave Gomboc
Date: 05:48:51 05/27/99
Go up one level in this thread
On May 27, 1999 at 08:12:33, Robert Hyatt wrote: >On May 27, 1999 at 03:19:50, Dave Gomboc wrote: > >>On May 27, 1999 at 03:16:58, Dave Gomboc wrote: >> >>>On May 27, 1999 at 02:40:10, Peter Kappler wrote: >>> >>>> >>>>Do any of you have any useful positions that you use for debugging your >>>>hashtables? >>>> >>>>I've been trying this one, which I think is pretty well known: >>>> >>>>8/k7/3p4/p2P1p2/P2P1P2/8/8/K7 w - - bm Kb1; >>>> >>>> >>>>Supposedly only Kb1 wins, but Grok likes Kb2. After 21 plies, the score jumps >>>>above +2 as Grok sees the f5 pawn dropping. >>>> >>>>Genius 6 and Fritz 5.32 both like Kb1 and give it a winning score (+2.5 to +3.0) >>>>immediately. >>>> >>>>I've seen this problem posted often enough that I trust that Kb1 is the only >>>>winning move. So not only is Grok not finding the best move, but it seems to be >>>>misevaluating Kb2. >>>> >>>>Does anybody else have problems with this position? >>>> >>>>Thanks, >>>>Peter >>> >>>You might (hand-)generate the co-ordinate square map for this position. Then >>>you will be able to look through the analysis of your program to see where it >>>screws up from, working back from where white can pick up the f-pawn. >>> >>>Dave >> >>Argh, sorry about the double post -- unresponsive GUI. :( >> >>I wanted to add, if this is the famous Fine position, then Kb2 is also winning, >>even though it gives away the "twisted diagonal opposition", so to speak. >>Reference "Computer Chess Compendium" (Levy, ed. 1998) for more details. I >>think it's discussed in 8.2 (though I wish I could find a copy to confirm this.) >> >>Dave > > >If this is fine position 70, Kb2 is a dead draw. Kb1 is the _only_ winning >move, and can be found in Fine's basic chess endings book. I'd hope that >David didn't get this wrong in his book, but you can easily confirm that it >draws, by trying Kb2 against crafty. It is hopeless after that move. If you >have looked at 'coordinating squares' it is easy to see why... I wrote in another post that I think I misremembered. Black has two moves to draw, though Fine gave only one of them. Averbakh analyzed only one of them, but now that I recall some more :-) I found the book that he analyzed it in, and it said the other move was also sufficient to draw. Dave
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