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Drawn position (?) that Stockfish 7 can't see is drawn



 
 
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  #1  
Old March 27th 16, 10:28 AM posted to rec.games.chess.computer
Derek Profts
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Default Drawn position (?) that Stockfish 7 can't see is drawn

1q6/1Pr2k2/1R2p3/3pPp1p/3P2pP/4P1P1/1R3K2/8 b - - 14 59

I believe that this position leads to a draw with correct play. Stockfish 7 64 bit has been crunching away at it for 48 hours or so and assesses it as -1.58

This is an endgame where White has a strong passed pawn but the material balance is that White is down a rook for a pawn. Schematic thinking tells me this is a draw. Stockfish has analyzed lines more than 50 ply long, and its current analyses run:

1. 47 [-1.58] 59.... Kf8 60.Ke2 Rf7 61.Kf2 Rh7 62.Ke2 Kg8 63.R2b5 Rf7 64. Rb2 Re7 65.R2b5 Kf8 66.Kf2 Rg7 67.Ke2 Rd7 68.Rb2 Rc7 69.R2b5 Rf7 70.Ke1 Rh7 71.Ke2 Rg7 72.Kf2 Rd7 73.Ke2 Kg8 74.Ke1 Rc7 75.Ke2 Rh7 76.Ke1 Kh8 77.Ke2 Rf7 78.Ke1 Re7 79.Ke2 Rh7 80.Kd2 Rg7 81.Ke2 Re7 82.Rb2 Rc7

2. 46 [-1.58] 59.... Kg8 60.Ke2 Kf8 61.R2b5 Rf7 62.Ke1 Rh7 63.Ke2 Rg7 64.Kf2 Rd7 65.Ke2 Kg8 66.Ke1 Rc7 67.Ke2 Rh7 68.Ke1 Kh8 69.Ke2 Rf7 70.Ke1 Re7 71.Ke2 Rh7 72.Kd2 Rg7 73.Ke2 Rc7 74.Rb2 Rd7 75.R2b5 Re7 76.Rb2 Rc7 77.Kd3 Rg7 78.Kd2 Kg8 79.R2b5 Kf8 80.Ke2 Rd7 81.Rb2 Rf7 82.Kf2

and Black has made no progress.
  #2  
Old March 27th 16, 01:59 PM posted to rec.games.chess.computer
Andy Walker[_3_]
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Posts: 51
Default Drawn position (?) that Stockfish 7 can't see is drawn

On 27/03/16 09:28, Derek Profts wrote:
1q6/1Pr2k2/1R2p3/3pPp1p/3P2pP/4P1P1/1R3K2/8 b - - 14 59
I believe that this position leads to a draw with correct play.
Stockfish 7 64 bit has been crunching away at it for 48 hours or so
and assesses it as -1.58


I think you're right. But this is one of those positions where
the sides can shuffle for 49 moves, then, seeing the draw imminent,
Black can sacrifice the f-pawn and shuffle for another 49 moves before
giving up R for P and then another long sequence before the Q vs 2R
ending is established drawn. [I'm not claiming this to be best play,
just the play that delays the inevitable the longest.] So you could
use another 48h and still not reach (49+49+49)*2 == 294 ply!

I had a position OTB some years ago where, in a bad position,
I could have [but didn't, out of cowardice in time trouble] sacrificed
a rook to reach one of those positions where Black's extra R was
pinned and attacked enough that Black could make progress only by
sacrificing it back, into a drawn opposite-coloured B ending. It
didn't surprise me that the computer didn't find the sacrifice,
and mis-evaluated it analysing forwards. But when I'd moved it on
a bit, it realised that it wasn't making progress, found the draw,
and then found it again when wound back to the start, presumably
because the draw was cached. Possibly something similar might be
possible here? If Stockfish can be persuaded to see the draw after
the f-pawn moves, it might then see it from the start. [I don't
have Stockfish, so can't try this myself, and in any case don't
want my computer tied up for 96 hours!]

--
Andy Walker,
Nottingham.
 




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