Author: Uri Blass
Date: 08:16:34 10/02/01
Go up one level in this thread
On October 02, 2001 at 10:53:06, Miguel A. Ballicora wrote:
>On October 01, 2001 at 15:02:35, Dieter Buerssner wrote:
>
>>On September 30, 2001 at 19:18:53, Miguel A. Ballicora wrote:
>>
>>>Here is a much tougher test from a real game
>>>(A. Sokolov - Korchnoi Tilburg 1987)
>>>Easy endgame? not quite!
>>>
>>>A. Sokolov miscalculated and made a mistake, played Rxc5? which ends up losing
>>>easily. Rb8 puts up a much tougher resistance with good chances of drawing.
>>>
>>>[D]8/2p3pp/8/1RrkP3/8/3K4/6PP/8 w - - am Rxc5;
>>>
>>>Not even Crafty gets this right (15 min K6-II 400mhz) Probably
>>>a problem evaluating the rook endgame because it sees a clear
>>>disadvantage in the pawn endgame.
>>
>>Is it really so easy? Unfortunately not for me :-( I tried a few lines fast
>>in Analyze mode. I ended in drawn position not only once.
>>
>>And - from a engine point of view. It is not too difficult, to give
>>the farer away passed pawn (or candidate, while the canditate is
>>probably much more difficult) a very high score. I am
>>however not convinced, that this only helps. I did quite some
>>experiments with mixed results. I think often, it will be a matter of
>>one tempo, and this seems to be very difficult to evaluate by me.
>>Many artifacts can arise, by scoring too high. Assume a won pawn endgame
>>with a passer at Q-side (the winning passed pawn). If you give this a
>>very high value, it may happen, that you try to defend the pawn,
>>instead of walking to the K-side and win there. In positions in the
>>search tree, you will see, that you lost one valuable pawn, but have
>>a much better K-position. So, it is not so easy to guarantee progression.
>>Especially, when I take into account, that my engine does not reach
>>very high search depths in pawn endgames with several unblocked pawns.
>>
>>Back to the position you posted:
>>I tried at 40 moves in 2 hours against Crafty.
>>First, I used an old batch file by an oversight, and gave Crafty also only
>>half of the hash of Yace.
>>
>>[Event "Computer chess game"]
>>[Site "?"]
>>[Date "2001.10.01"]
>>[Round "1"]
>>[White "Yace 0.99.56"]
>>[Black "wcrafty-17.10"]
>>[Result "1/2-1/2"]
>>[TimeControl "40/7200"]
>>[FEN "8/2p3pp/8/1RrkP3/8/3K4/6PP/8 w - - 0 1"]
>>[SetUp "1"]
>>
>>{--------------
>>. . . . . . . .
>>. . p . . . p p
>>. . . . . . . .
>>. R r k P . . .
>>. . . . . . . .
>>. . . K . . . .
>>. . . . . . P P
>>. . . . . . . .
>>white to play
>>--------------}
>>1. Rxc5+ Kxc5 2. Ke4 h5 3. h4 c6 4. g3 g6 5. g4 hxg4 6. Kf4 Kd5 7. Kxg4
>>Kxe5 8. Kg5
>>{adj., TB position} 1/2-1/2
>>
>>I repeated with Crafty 17.14 and enabled the PGN of Yace with scores:
>>
>>[Event "Computer chess game 40 7200 +0 0 0"]
>>[Site "?"]
>>[Date "2001.10.01"]
>>[Round "1"]
>>[White "Yace 0.99.56 MLbook"]
>>[Black "crafty"]
>>[Result "1/2-1/2"]
>>[SetUp "1"]
>>[FEN "8/2p3pp/8/1RrkP3/8/3K4/6PP/8 w - -"]
>>[WhiteElo "0"]
>>[BlackElo "0"]
>>[Timecontrol "40 7200 +0 0 0"]
>>[Time "Mon Oct 01 20:05:13 2001"]
>>[LogFile "logs\yace0562.log"]
>>
>>1. Rxc5+ {-0.30/15 217s} Kxc5 {181s} 2. Ke4 {-0.24/17 215s} Kc6 {181s} 3. Kd4
>>{-0.29/15 161s} Kd7 {182s} 4. Kd5 {-0.42/16 190s} g5 {189s} 5. e6+
>>{0.00/16 118s} Ke7 {182s} 6. Kc6 {0.00/16 107s} Kxe6 {182s} 7. Kxc7
>>{0.00/19 139s} Kf5 {181s} 8. Kd6 {0.00/62 80s} 1/2-1/2 {adj.}
>>
>>I think, 4...c6+ would have won. (Crafty score for g5 was around 1 for black).
>>
>
>Almost anything wins, but the bad move is 7... Kf5 (As far as I can see blinfold
>:-). Why allowing the white king to get closer? Keep the bKing on the e file so
>you always have a chance to penetrate on f2. Do _NOT_ move the black
>king until the pawns are fixed. Stay put with the king, advance the
>pawns and fix them, even if you trade one (keep a g pawn!). Go then and eat
>it/them. If white king wants to race to their own side you "shoulder it". When
>Kc4, play Ke4. If Kc3 then Ke3 and then Kf2. It is pretty easy once you follow
>this simple plan. I am surprised that Crafty did not find it by search!
I tend to believe that if yace says 0.00 for 7.Kxc7 at depth 19 when the
position is almost tablebase position
(KPP vs KPP after Kxc7) then it is a draw.
You did not give a move for black instead of 7...Kf5
The idea of Kc4 and Kc3 for white seems to be bad and white should try to go for
the black pawns by means of Kd7 or even Kd8 after moves like 7...h5.
Uri
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