Author: José Antônio Fabiano Mendes
Date: 11:15:10 04/03/00
Go up one level in this thread
On April 03, 2000 at 12:11:53, KarinsDad wrote: >On April 03, 2000 at 11:58:30, Dave Gomboc wrote: > >>On April 03, 2000 at 11:53:34, KarinsDad wrote: >> >>>On April 03, 2000 at 11:44:44, blass uri wrote: >>> >>>>On April 03, 2000 at 10:54:21, KarinsDad wrote: >>>> >>>>>On April 03, 2000 at 06:10:21, Jeremiah Penery wrote: >>>>> >>>>>>There is a problem with tablebases. >>>>>> >>>>>>No, they don't produce wrong answers. And no, they don't make engines play >>>>>>weaker. The problem is that engines would rather be -9 and not in TBs than see >>>>>>mate against itself and be in TBs. I have one good example, from a game my >>>>>>modified Crafty played on ICC, and I may try to find it, if possible. But I do >>>>>>remember what happened: >>>>>> >>>>>>I had something like a knight and a pawn, and my opponent had 2 knights and a >>>>>>pawn, about to promote. I had the choice to let him promote, and have a score >>>>>>of about -9. I would easily lose. My other choice was to sacrifice my knight >>>>>>for his pawn, and enter a lost KNNKP endgame, somewhere around Mate in 75. I >>>>>>would not easily lose this, unless my opponent had the TB, in which case it >>>>>>could be a draw by 50-moves. >>>>> >>>>> >>>>>Excuse me, but what am I missing? >>>>> >>>>>Isn't a KNNKP ending almost always a draw (assuming nothing special) if the side >>>>>with the pawn wants it to be? Cannot the side with the pawn force the draw >>>>>(regardless of 50 move rule) since KNNK is a draw? >>>> >>>>No >>>>The side with the two knight can sometimes win against a pawn because the side >>>>with the 2 knights can avoid stalemate when there is a pawn because the pawn can >>>>move and cannot avoid stalemate if he use the same plan when there is no pawn. >>>> >>>>Uri >>> >>>Huh? >>> >>>The side with the pawn pushes the pawn. If the other side captures, it is KNNK. >>>If the other side blocks it with a knight, then it is KNK (effectively). The >>>side with the pawn sits his king in the middle of the board and jumps back and >>>forth. If the side with the knights comes after the king, then the side with the >>>king pushes the pawn again. >>> >>>This still seems like it can be a forced draw by the side with the pawn. >>> >>>Now, of course, if you have some special position where the two knights can mate >>>the opposing king because it is trapped against the edge due to his own pawn, >>>then I can understand that it COULD happen. But that does not seem to be the >>>case in the example sited since he is talking about a forced mate in 75. >>> >>>KarinsDad :) >> >>There are a large percentage of wins in KNNKP. The pawn must be blockaded >>before it gets too close to the promotion square. The specific distance depends >>on the file it is on. IIRC, this was extremely well-analyzed by a human long >>before a tablebase was generated for it. >> >>Dave > >Ok, so what you are saying is that if the pawn is sufficiently advanced, then >the side with the pawn can force the draw. Otherwise, the side without the pawn >can first blockade the pawn and later put the opposing king in check often >enough so that even though the pawn can push, the king is forced into the corner >and checkmated before the pawn can queen. > >Is this correct? > >KarinsDad :) White mates in 98 moves [D]N6N/p7/8/8/8/8/8/K6k w - - Optimal move: 1.Nc7 http://chess.liveonthenet.com/chess/endings/ JAFM
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