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Subject: Re: Rybka PV bug (hash table?)

Author: Vasik Rajlich

Date: 01:14:48 12/20/05

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On December 20, 2005 at 00:56:02, Neil Schemenauer wrote:

>I think I've found a bug in Rybka Beta (maybe in Preview as well).
>The engine comes up with an invalid PV (0-0-0 when castling is not
>possible).  It could be a hash-table bug since to reproduce it I
>have to start from the beginning of the game using the analysis mode
>of the Shredder UI.
>
>The full game follows.  Any comments on my (lack of) style would
>appreciated.  I was playing against CSTal 2 with "reduce strength"
>set to 1, the weakest setting.  I managed to win against that
>setting for the first time today and this game was one of my wins.
>The knight sac was probably not the best idea but I wanted to see if
>I could pull it off.  Onward to level 50. :-)
>
>
>[D]rn2k2r/ppqbb1pp/3p4/3n2N1/1P3B2/P2B4/2PQ1PPP/R4RK1 b kq -
>
>Engine: Rybka 1.0 Beta 32-bit (80 MB)
>by Vasik Rajlich
>
>8.00   0:01   +1.48    17...Nc6 18.Bg3 Ne5 19.Ne4 Nf6 (44.744) 25
>
>9.00   0:03   +1.58    17...Nc6 18.Bg3 Ne5 19.Bxh7 O-O-O
>                       20.Qxd5 (100.680) 27
>
>10.00  0:08   +1.17    17...Nc6 18.Bg3 Ne5 19.c4 Bxg5
>                       20.Qxg5 Nxd3 21.Qxd5 (227.570) 26
>
>10.02  0:10   +1.34    17...Nxf4 18.Qxf4 O-O-O 19.Nf7 Rhf8
>                       20.b5 d5 (291.442) 29
>
>11.01  0:16   +1.64    17...Nxf4 18.Qxf4 O-O-O 19.Rae1 Nc6
>                       20.Ne6 Bxe6 21.Rxe6 Bf6 (468.531) 31
>
>12.01  0:21   +1.66    17...Nxf4 18.Qxf4 O-O-O 19.Rae1 Nc6
>                       20.Ne6 Bxe6 21.Rxe6 Bf6 22.Qe3 (678.258) 32
>
>
>
>
>[Event "?"]
>[Site "?"]
>[Date "2005.12.19"]
>[Round "?"]
>[White "Neil Schemenauer"]
>[Black "CSTal 2"]
>[Result "1-0"]
>
>1. e4 d6 2. d4 e5 3. Nf3 f6 4. Nc3 Nc6 5. d5 Nb4 6. a3 Na6
>7. b4 Bd7 8. Be2 Be7 9. O-O f5 10. Bd3 f4 11. Ne2 Nb8
>12. Nxf4 exf4 13. Bxf4 Nf6 14. e5 Nxd5 15. exd6 cxd6
>16. Qd2 Qc7 17. Ng5 Nf6 18. Rfe1 Nc6 19. c4 Kf8 20. Qc2 Nd4
>21. Qc3 Nf5 22. Ne6+ Bxe6 23. Rxe6 Nh4 24. c5 Qc6 25. f3
>Nxf3+ 26. gxf3 Nh5 27. Be4 Qd7 28. cxd6 Qxe6 29. dxe7+ Qxe7
>30. Be3 Kf7 31. Bd5+ Ke8 32. Re1 Kd8 33. Qd2 Qd7 34. Rd1
>Nf6 35. Bxb7 Qxd2 36. Rxd2+ Kc7 37. Bxa8 Rxa8 38. Bd4 a6
>39. Kg2 Kc6 40. Kg3 Rd8 41. Rc2+ Kd6 42. Bxf6 gxf6 43. Rd2+
>Ke7 44. Rxd8 Kxd8 45. Kg4 Ke7 46. Kf5 Kf7 47. f4 h5 48. a4
>Ke7 49. b5 axb5 50. axb5 Ke8 51. b6 Kd7 52. Kxf6 h4 53. f5
>Kc6 54. Ke7 h3 55. f6 Kxb6 56. f7 Kc5 57. f8=Q Kc4 58. Qf3
>Kb4 59. Qxh3 Kc4 1-0

Thanks. I can reproduce it here, it will be fixed.

BTW 12. Nxf4 probably isn't correct :-)

Vas



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