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Subject: Re: 2 mates to solve

Author: Heiner Marxen

Date: 15:47:58 05/27/01

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On May 26, 2001 at 15:46:20, Uri Blass wrote:

>[D]2kr3r/ppp2p2/7p/8/6bq/2Q5/PPP3K1/RNB1N3 b - - 0 1
>
>This position is from a practical game of Deep Fritz in the ICC tournament(round
>1).
>
>The opponent resigned but Deep Fritz can probably force mate in 9 moves by
>21...Rhg8 22.Bf4 Bh3+ 23.Kf3 Qg4+ 24.Ke3 Qg1+ 25.Kf3 Bg4+ 26.Ke4 f5+ 27.Ke5 Qb6
>28.Qxc7+
>Kxc7 Nf3 Rge8#
>
>At least this is the opinion of yace.
>
>Uri

Yes, according to Chest that is completely correct.  It is a mate in 9
(i.e. there is no shorter forced mate), and the above PV is part of Chest's
solution tree, i.e. is a valid PV.

Chest finds a total of three key moves, which force the mate in 9:

Rde8 Qxh8  Rxh8  Nc3   Rg8   Bg5   Qxg5   Ne4   Qd5    Kf1   Qxe4   Kf2  Qe2+
Kg1   Bf3+   Ng2  Qxg2#

Rhe8 Be3   Bh3+  Kf3   Rd1   Ke2   Bg4+   Nf3   Qh2+   Kxd1  Bxf3+  Kc1  Qh1+
Bg1   Qxg1+  Kd2  Qd1#

Rhg8 Bf4   Bh3+  Kf3   Qg4+  Ke3   Qg1+   Ke2   Bf1+   Kf3   Qg4+   Ke4  Rge8+
Qe5   f5+    Ke3  Qe2#

Rhg8 appears to be a bit more forced, than the other two.

That was not easy for Chest: on a K7/600 with 350 MB hash it needed 18.7 hours.

Cheers,
Heiner



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