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Old July 22nd 17, 09:16 AM posted to rec.games.chess.computer,rec.games.chess.analysis
Martin Brown[_2_]
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Posts: 3
Default Engine puzzle position

On 21/07/2017 21:23, Rainer wrote:
On 21/07/2017 17:14, Martin Brown wrote:

I have stumbled upon a position where quite a few engines - I thought
at first it was just x64 types but Fritz 10 also sees the same
phantom "Good move" which evaluates as a draw where none exists. The
position is hopelessly lost but that isn't the point. Something is
wrong.

I found it analysing a lost game where there was a clear and bizarre
discontinuity in the evaluation function that made no sense to me.

Crafty x64 23.05 also sees the wrong right move but x32 20.14 is OK.

r2r4/1p2p1kp/p5p1/3BNbPn/8/2N4P/PPP2P2/R3K2R b KQ - 0 21

It is a close run thing between 22. ... Rac8, or 22 ... Nf4 but the
phantom move which evaluates as a draw is 22. ... Bc8

If you actually play this move Bc8 then the evaluation becomes
correct again with white to move. There is something odd about this
position that breaks some engines. Any ideas what it might be?

My guess is that it is some sort of draw by repetition bug common to
several of the engines since the offending thread displays as just a
single move with no continuation line : [...]


You didn't post the game, so I have to ask: is there a position
repetition after 21...Bc8? If so, a zero score would be acceptable.


The material balance is such that the winning side should not be looking
for a draw and the losing side has no way to force perpetual check. The
score for the move 22. ... Bc8 is totally anomolous (as is the fact that
it does not have any continuation line in the annotation).

It might be relevant that the strongest continuation for white is 0-0-0
and there may be a bug in the logic around queens side castling
somewhere. Almost none of the engines see anything other than "best" is
21. ... Bc8 0.0 (and see no further than that)

This is the result of applying blundercheck threshold 20cp 4s to the
entire game (opening blunder in blitz) but played on in the hope of
winning something back.

[Event "Blitz 5m+5s-4m+2s"]
[Site "?"]
[Date "2017.07.21"]
[Round "?"]
[White "Deep Fritz 14"]
[Black "Martin"]
[Result "1-0"]
[ECO "B08"]
[WhiteElo "1812"]
[BlackElo "1815"]
[PlyCount "75"]
[TimeControl "240+2"]

1. d4 {0} d6 {4}
2. e4 {0} Nf6 {2}
3. Bd3 {0} g6 {2}
4. Nf3 {0} Bg7 {1}
5. h3 {0.23/20 0 last book move} Nbd7 {0.20/18 2}
6. Nc3 {0.20/21 0} O-O {0.20/20 1}
7. e5 {0.20/20 0} dxe5 {0.47/21 6}
({Deep Fritz 14 x64:} 7... Ne8 8. Qe2 c5 9. Bg5 cxd4 10. exd6 Nxd6 11.
Bxe7 Qb6 12. Bxf8 Nxf8 13. Ne4 Nxe4 14. Bxe4 Qb4+15. Nd2 Qxb2 16. O-O
Ne6 17. Rab1 Qxa2 18. Bxb7 Bxb7 19. Rxb7 Qxc2 20. Qf3 Rf821. Rd1 a5
{0.20/20})
8. dxe5 {0.38/21 0} Nh5 {1.02/18 8}
({Deep Fritz 14 x64:} 8... Ne8 9. Bc4 {0.38/21})
9. g4 {0.89/18 0} Nf4 {3.61/20 7}
({Deep Fritz 14 x64:} 9... Nxe5 10. gxh5 Nxd3+ 11. Qxd3 Bf5 12. Qe2 Qd6
13. O-O Bxh3 14. Re1 Bxc3 15. bxc3 Qd5 16. h6 Rfd8 17. Rb1 b6 18. c4 Qf5
19. Qe5 Qxe5 20. Nxe5 Bf5 21. Nc6 {0.89/18})
10. Bxf4 {3.50/19 0} f6 {4.26/19 23}
({Deep Fritz 14 x64:} 10... Nc5 11. Be2 Ne6 12. Be3 Bd7 13. Qd2 Bc6 14.
O-O-O Qxd2+ 15. Bxd2 Rad8 16. Be3 b6 17. Rxd8 Rxd8 18. Rd1 Rxd1+ 19.
Bxd1 Bxf3 20. Bxf3 Bxe5 21. Kd2 Bf4 22. Nb5 Bxe3+ 23. fxe3 a6 {3.50/19})
11. exf6 {4.16/18 0} Nxf6 {5.42/22 2}
({Deep Fritz 14 x64:} 11... exf6 12. Bc4+ Kh8 13. O-O f5 14. g5 Qe7 15.
Bb3 Nc5 16. Nd5 Qe4 17. Re1 {4.16/18})
12. Bc4+ {5.42/22 0} Kh8 {5.42/21 2}
13. Qxd8 {5.42/21 0} Rxd8 {5.29/20 3 Deep Fritz 14 doubles}
14. Bxc7 {5.27/19 0} Rd7 {6.15/20 6}
15. Be5 {5.94/19 0} a6 {6.29/19 10}
16. g5 {5.44/19 0} Nh5 {5.49/20 4}
17. Be6 {5.20/22 0} Rd8 {5.20/21 5}
18. Bd5 {5.12/19 0} Bxe5 {5.65/21 34}
19. Nxe5{5.47/19 0} Kg7 {5.70/19 19}
20. Bb3 {4.74/19 0} Bf5 {4.74/18 16}
21. Bd5 {0.00/28 0} ({Deep Fritz 14 x64:} 21. Ne2 Rd6 {4.74/18})
21... Rab8 {5.18/19 6} ({Deep Fritz 14 x64:} 21... Bc8 {0.00/28})
22. a4 {3.15/19 0}
({Deep Fritz 14 x64:} 22. O-O-O Nf4 23. h4 Rbc8 24. Bf3 Rd6 25. Rhe1
Rxd1+ 26. Rxd1 Rc7 27. Rd4 Nh3 28. Be4 Nxf2 29. Bxf5 gxf5 30. Rf4 Rxc3
31. bxc3 {5.18/19})
22... e6 {4.24/22 8}
({Deep Fritz 14 x64:} 22... Bxc2 23. Bf3 Nf4 24. Ne2 Nd3+ 25. Nxd3 Bxd3
26. Rc1 b5 27. a5 Bc4 28. Rc3 Rbc8 29. b3 Be6 30. Re3 Rd6 31. Nf4 Rc1+
32. Ke2 Rc2+ 33. Kf1 {3.15/19})
23. Be4 {4.24/21 0} Nf4 {4.24/19 21}
24. Rc1 {3.96/18 0} Rd4 {4.59/22 13}
25. Bxf5 {4.50/21 0} exf5 {4.50/21 3}
26. Rd1 {4.48/19 0} Rb4 {5.68/19 13}
({Deep Fritz 14 x64:} 26... Rdd8 27. Nd3 Ne6 28. h4 Nd4 29.Kd2 b5 30.
axb5 axb5 31. Ne2 Ra8 32. Nxd4 Rxd4 33. Ra1 {4.48/19})
27. Rd7+ {5.68/19 0} Kg8 {5.59/17 7}
28. Nd5 {4.10/18 0}
({Deep Fritz 14 x64:} 28. Kd2 Rxb2 29. Re1 Nxh3 30. Nd3 Nxg5
31. Nxb2 Nf3+ 32. Ke2 Nxe1 33. Kxe1 Re8+ 34. Kf1 b6 35. Nd5 Re6
36. Nd3 b5 37. Nc5 {5.59/17})
28... Re4+ {5.45/21 9}
({Deep Fritz 14 x64:} 28... Nxd5 29. Rxd5 Rxb2 30. Nd7 Re8+ 31. Kd2 Rc8
32. Nf6+ Kh8 33. Rc1 {4.10/18})
29. Kf1 {5.28/18 0} Rxe5 {6.33/20 8}
30. Nxf4 {6.14/19 0} Re4 {7.97/20 10}
({Deep Fritz 14 x64:} 30... b5 31. Nd3 Re4 32. axb5 axb5 33. Kg2 Rbe8
34. Ra1 R8e7 35. Ra8+ Kg7 36. Rxe7+ Rxe7 37. Rb8 Re2 38. Rb7+ Kg8 39.
Nb4 Re5 40. Kf3 Rc5 41. c3 Re5 42. Nc6 Re6 43. Nd4 {6.14/19})
31. Nd5 {7.77/20 0} Rxa4 {13.94/20 3}
({Deep Fritz 14 x64:} 31... Kf8 32. Kg2 {7.77/20})
32. Nf6+ {13.53/20 0} Kf8 {12.20/18 5}
33. Rxh7 {8.61/18 0}
({Deep Fritz 14 x64:} 33. Nxh7+ Kg8 34. Nf6+ Kf8 35. Kg2 Rc8 36. Re1 Re4
37. Nxe4 fxe4 38. Rxb7 Rc4 39. Rd1 Rc8 40. Rd6 e3 41. fxe3 a5 42. Rf6+
Kg8 43. Rxg6+ Kf8 44. Rf6+ Kg8 45. c3 Rc5 46. h4 Rd5 47. Ra6 Rd2+ 48.
Kf3 {12.20/18})
33... Rd8 {12.54/21 13}
({Deep Fritz 14 x64:} 33... Ra1+ 34. Kg2 Rxh1 35. Rh8+ Kf7 36. Rxb8 Ra1
37. Rxb7+ Ke6 38. Rb6+ Kf7 39. c4 a5 40. c5 Rc1 41. c6 a4 42. Nd5 Ke6
43. Nf4+ Kd6 44. Nxg6 Kc5 45. Rb8 Kd6 46. h4 Rxc6 47. h5 Rc4 48. Rd8+
Ke6 49. Re8+ {8.61/18})
34. Kg2 {11.99/19 0} Rd2 {17.14/23 10}
({Deep Fritz 14 x64:} 34... Rd6 35. Re1 Re4 36.Nxe4 fxe4 37. Rxb7 Rd4
38. Rb6 Kg7 39. Rxa6 Rd5 40. Ra7+ Kf8 41. Rxe4 Rxg5+ 42.Rg4 Rb5 43. Rc4
Rb8 44. Rcc7 Kg8 45. b3 Rd8 46. h4 Kf8 47. Ra6 Ke8 48. Rxg6 Kf8
49. h5 Rd2 50. Rgg7 {11.99/19})
35. Re1 {17.05/21 0} Re4 {15.24/23 7}
36. Nxe4 {14.68/22 0} fxe4 {14.28/21 2}
37. Rxb7 {12.59/18 0} e3 {21.93/23 6}
({Deep Fritz 14 x64:} 37... Rd4 38. Rb6 Kf7 39. Rf6+ Kg7 40. Rxa6 Rd5
41. Rxe4 Rb5 42. Ra7+ Kf8 43. b3 Rxg5+ 44. Rg4 Rd5 45. Rxg6 Rd8 46. c4
Rb8 47. Rf6+ Kg8 48. Rd6 Kf8 49. c5 Rc8 50. c6 Ke8 51. Rg6 {12.59/18})
38. Rxe3 {19.94/20 0} 1-0


Just in case it is relevant Deep Fritz is running on a 4 core i7 3770K
but the other failing chess engines are mostly single core ones.

--
Regards,
Martin Brown