Author: Miguel A. Ballicora
Date: 11:48:38 10/02/01
Go up one level in this thread
On October 02, 2001 at 11:16:34, Uri Blass wrote:
>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.
Thanks for pointing that out. I did not notice that. Now that I think White
might have this defense:
7 ... h5
8. Kd8 g4
9. g3!!
or
7.... h5
8.Kd8 h4
9. h3!!
and it is a draw. If I trade one pawn black wins but white avoids it!
Black should be careful with the tempi before that. So, not almost everything
wins. The position is interesting and I will analyze it carefully later.
I should be more careful with the analysis, sorry, but if I wait until
I have a board in front of me and time on my hands I will never respond.
Regards,
Miguel
>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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