Author: Jarkko Pesonen
Date: 05:58:51 02/04/04
Re: How many programs can select the 1......h6! drawish move ? http://chessprogramming.org/cccsearch/ccc.php?art_id=295554 If there ever was a hole in crafty's code, was it fixed as you intended to do? Jarkko Some programs would select to move the king or 1....h5? which allow white to penetrate, but 1....h6! would be the correct move by just sitting tight, and there is no danger of Whites's king penetrating. [D]8/1p2k2p/4p3/1PP2pp1/3P4/7P/5KP1/8 b - - 0 1 Posted by : Robert Hyatt on May 07, 2003 at 10:46:49 On May 06, 2003 at 11:14:19, José Carlos wrote: >On May 06, 2003 at 08:55:07, Robert Hyatt wrote: > >>On May 06, 2003 at 07:05:02, Jarkko Pesonen wrote: >> >>>Crafty 19.3 ends up in this position >>> white black >>> 1 d5 e5 >>> 2 c6+ bxc6 >>> 3 bxc6+ Kc8 >>> 4 d6 e4 >>> 5 Kd4 h5 >>> 6 g4 hxg4 >>> 7 hxg4 f4 >>> 8 Kxe4 ... >>> >>>[D]2k5/8/2PP4/6p1/4KpP1/8/8/8 b >>> >>> 21-> 1:40 6.47 1. ... Kd8 2. Kd4 Kc8 3. Kd3 Kd8 4. >>> Ke4 Kc8 5. Kf3 Kd8 6. Kf2 Kc8 7. Ke2 >>> Kd8 8. Kd3 Kc8 9. Kc3 Kd8 10. Kd2 Kc8 >>> 11. Ke1 f3 >>> >>>Seems that crafty isn't doing any progress and score is totally wrong(seems to >>>be draw). >>> >>>Is there an easy way to fix this? >>>Or is this some kind off odd situation that is so rare that it is not >>>worth fixing? >>> >>>Jarkko >> >> >>That can be fixed. It is the classic problem of two connected passed pawns >>being valued too high in a king and pawn ending. If they were separated, >>white would win easily. But together, they can be stopped. I will look >>at this and fix it. The code is already there, it just has a hole that I >>apparently overlooked. > > These kind of position is very tricky. In some cases, white can forget about >the black pawns and go with the king to help his pawns. AFAIK it can only be >safely solved by search. > > José C. I agree. But the way it is done, the error rate is higher than it should be, I've explained why previously. Two connected passers are not what you want in a king and pawn ending if your opponent has two passers that are separated. I have code to do this right, but it has a hole in it that I had overlooked...
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