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Subject: Re: how to report the length of a mate

Author: Mike Byrne

Date: 17:49:50 08/21/02

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On August 21, 2002 at 18:33:16, Jeroen van Dorp wrote:

>[D]8/Q7/K7/5r2/5p2/8/6k1/8 w - - 0 1
>Mate in 103 / Mate in 104
>
>I used Wilhelm to find out the longest mate wK+Q against bK+R+P from my
>tablebases. It gave the above position.
>
>Wilhelm calls this a mate in 104 - mate on move 104? - but if I feed the
>position in CB8 the tablebase engine calls it a mate in 103.
>
>Both use the same TB's; isn't there a convention how to call a mate read out
>from the TB's? Or is it up to the GUI programmer to report it either way?
>
>J.

I always attribute this descrepancy to user error.  The user has to know if the
program announce mate before the move or after the move.  It's a mate in 104
BEFORE 1. Qg7+.  It's a mate in 103 AFTER 1.Qg4.  The convention should be
standardize and I would guess most folks would prefer the BEFORE count - the way
Chessmaster and Crafty do it.

1. Qg7+ Kf1 2. Qa1+ Kg2 3. Qa2+ Kg3 4. Qg8+ Kf2 5. Qe6 Rg5 6. Qf6
Rg4 7. Qd4+ Kg3 8. Qg1+ Kf3 9. Qh2 Rg3 10. Qh4 Rg4 11. Qh3+ Rg3 12.
Qf5 Rg4 13. Kb7 Kg3 14. Qe5 Kh3 15. Qf6 Kg3 16. Qd6 Kh3 17. Qd3+
Kg2 18. Qd4 Rh4 19. Qd2+ Kf1 20. Qd5 Kf2 21. Qe4 Rg4 22. Qd4+ Kg3
23. Qg1+ Kf3 24. Qh2 Rg2 25. Qh4 Rg4 26. Qh3+ Rg3 27. Qf5 Rg2 28.
Kc6 Rd2 29. Kc5 Ke3 30. Qg5 Rd3 31. Qe7+ Kf3 32. Qh4 Rd2 33. Kc4
Ke3 34. Qe1+ Re2 35. Qg1+ Ke4 36. Qg4 Rc2+ 37. Kb4 Rh2 38. Kc3 Ke3
39. Qe6+ Kf3 40. Kd3 Rg2 41. Qh3+ Rg3 42. Qh2 Kg4+ 43. Kd2 Re3 44.
Qh8 Rh3 45. Qg8+ Kf3 46. Qg1 Rg3 47. Qd1+ Ke4 48. Qc2+ Ke5 49. Qc5+
Kf6 50. Ke2 Re3+ 51. Kf2 Rg3 52. Qd5 Re3 53. Kg2 Rg3+ 54. Kh2 Re3
55. Qg8 Rg3 56. Qh8+ Kg5 57. Qg7+ Kf5 58. Qh6 Ke5 59. Qf8 Re3 60.
Qh8+ Ke6 61. Qh6+ Kf5 62. Qh5+ Ke4 63. Qg6+ Ke5 64. Qg5+ Ke4 65.
Qf6 Re2+ 66. Kh3 f3 67. Qc3 Rg2 68. Qc1 Kd3 69. Qa3+ Ke4 70. Qc3
Rg5 71. Qc6+ Kf4 72. Qc1+ Kf5 73. Qe3 Kf6 74. Qxf3+ Ke6 75. Qc6+
Ke5 76. Qc5+ Kf6 77. Qd6+ Kf5 78. Qe7 Rg6 79. Qh7 Kg5 80. Kg3 Rf6
81. Qe4 Rf5 82. Qe7+ Rf6 83. Qd8 Kf5 84. Qd5+ Kg6 85. Kg4 Kg7 86.
Qd8 Kf7 87. Kg5 Re6 88. Kf5 Re7 89. Qd5+ Kg7 90. Kg5 Rf7 91. Qd8
Rf1 92. Qd4+ Kf8 93. Kg6 Ke7 94. Qe4+ Kd6 95. Qd3+ Kc5 96. Qxf1 Kd5
97. Qa6 Kd4 98. Kf5 Kc3 99. Qb5 Kc2 100. Kf4 Kc1 101. Qb4 Kd1 102.
Qb2 Ke1 103. Ke3 Kd1 104. Qd2#



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