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

Author: John Merlino

Date: 15:54:41 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.

Chessmaster 9000 reports "Mate in 104", because it is 104 moves FROM THIS
POSITION.

I suppose it is really a GUI issue -- I believe the Tigers would report Mate in
103.

However, just for the curious, best play will result in a 50-move draw.

[Event ""]
[Site ""]
[Date "2002.8.21"]
[Round ""]
[White "Chessmaster"]
[Black "Chessmaster"]
[TimeControl "40/7200"]
[Result "1/2-1/2"]
[Setup "1"]
[FEN "8/Q7/K7/5r2/5p2/8/6k1/8 w - - 0 1"]

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.Qb2+ Kg3
20.Qe5 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.Kb3 Rh2
38.Kc3 Ke3 39.Qe6+ Kf3 40.Kd3 Rg2 41.Qh3+ Rg3 42.Qf1+ Kg4+ 43.Kd2 Re3
44.Qg2+ Rg3 45.Qc6 Rh3 46.Ke1 Re3+ 47.Kf2 Kg5 48.Qa4 Rg3 49.Qc2 Kf6
50.Qc5 Ke6 1/2-1/2

Black's pawn is not "forced" to move until move 66.

jm



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