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Subject: What to do when hash table returns a Mate value?

Author: Anthony Cozzie

Date: 11:07:59 01/17/03

Last night Zappa played a most annoying game vs sfarrellc:

[Event "ICS Rated Standard match"]
[Site "chessclub.com"]
[Date "2003.01.17"]
[Round "-"]
[White "Zappa"]
[Black "sfarrellc"]
[Result "*"]
[WhiteElo "2231"]
[BlackElo "2185"]
[TimeControl "2700+10"]

1. e4 Nc6 2. d4 e5 3. dxe5 Nxe5 4. Nf3 Nxf3+ 5. Qxf3 Qf6 6. Qe3 Bb4+ 7. c3
Ba5 8. Qg3 Ne7 9. Bg5 Qg6 10. Nd2 f6 11. Bf4 d6 12. Bb5+ c6 13. Bd3 Qxg3
14. hxg3 Bc7 15. Nc4 Kd7 16. O-O-O h6 17. Bxd6 Bxd6 18. Be2 Kc7 19. Nxd6
Be6 20. Bc4 Bxc4 21. Nxc4 Rad8 22. Kc2 Rde8 23. f3 Nc8 24. Rd4 Rd8 25. Rhd1
Rxd4 26. Rxd4 Rd8 27. Rxd8 Kxd8 28. e5 fxe5 29. Kd3 Kc7 30. Nxe5 c5 31. Ke4
Kd6 32. f4 Ke6 33. f5+ Ke7 34. g4 Nb6 35. b3 Nd7 36. Nxd7 Kxd7 37. Kd5 b6
38. a4 Ke7 39. Kc6 Ke8 40. Kb7 Kd7 41. Kxa7 Kc6 42. Kb8 Kd5 43. Kc7 c4 44.
bxc4+ Kc5 45. g3 Kxc4 46. Kxb6 Kd5 47. a5 Ke4 48. a6 Kf3 49. a7 Kxg4 50.
a8=Q Kxf5 51. Qf8+ Ke4 52. Qxg7 Kd3 53. Qxh6 Ke2 54. Qf4 Kd3 55. Qe5 Kd2
56. Qe6 Kd1 57. Qa2 Ke1 58. Qc2 Kf1 59. Qh2 Ke1 60. Qc2 Kf1 61. Qh2 Ke1 62.
Qg2 Kd1 63. Qa2 Ke1 64. Qg2 Kd1 65. Qf2 Kc1 66. Qa2 Kd1 67. Qf2 Kc1 68. Qa2
Kd1 69. Qg2 Ke1 70. Kb5 Kd1 71. Qf2 Kc1 72. Qe2 Kb1 73. Qg2 Kc1 74. Qe2 Kb1
75. Qg2 Kc1 76. Qf2 Kd1 77. Kc5 Kc1 78. Kb5 Kd1 79. Kc5 Kc1 80. Qe2 Kb1 81.
Kb5 Kc1 82. Qd3 Kb2 83. Qd2+ Kb1 84. Qd1+ Kb2 85. Qd2+ Kb1 86. Qd1+ Kb2 87.
Qd3 Kc1 88. Ka6 Kb2 89. Qd2+ Ka1 90. Kb6 Kb1 91. Qd1+ Kb2 92. Qd2+ Ka1 93.
Qd1+ Kb2 94. Qd2+ Ka1 95. Qd1+ Kb2 [1/2]

In the end, Zappa has KQPP v K, and calculated a mate in 20 or some other trash.
   Somehow, though, a few of the key transposition table entries were wrong, or
something.  Currently, whenever Zappa sees a mate in the TTable, it returns
instantly with that score.  Zappa saw a mate on every square (in 1 ply) but was
unable to make progress (and yes, I have a progress factor).  So the questions
are:

1) is there just a bug here?
2) if you get a mate score from the hash table, what do you do?

anthony

• Re: What to do when hash table returns a Mate value? scott farrell 15:54:24 01/17/03
• Re: What to do when hash table returns a Mate value? Robert Hyatt 14:08:11 01/17/03
  • Re: What to do when hash table returns a Mate value? Dieter Buerssner 14:27:22 01/17/03
    • Re: What to do when hash table returns a Mate value? Dave Gomboc 17:40:25 01/18/03
      • Re: What to do when hash table returns a Mate value? Robert Hyatt 19:32:29 01/18/03
        • Re: What to do when hash table returns a Mate value? Dave Gomboc 00:29:23 01/20/03
    • Re: What to do when hash table returns a Mate value? Robert Hyatt 19:32:41 01/17/03
• Re: What to do when hash table returns a Mate value? David Rasmussen 12:59:18 01/17/03

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