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Subject: Re: Mate in 18 moves?

Author: Frank Schneider

Date: 11:13:20 01/10/98

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On January 09, 1998 at 11:11:14, Ed Schröder wrote:

>Mate in 18 moves?
>
>I am busy to release some new EPD test sets in the Rebel9 subscription
>area. One the EPD sets is a 200 positions selection from the Austrian
>Modul magazine with lots of funny old stuff.
>
>I then came across the following cool "mate in 18(?)" position:
>
>[Event "?"]
>[Site "3/93-51 Matt in wieviel?"]
>[Date "1992.01.01"]
>[Round "?"]
>[White "Kristian Skoeld: Sc"]
>[Black ""]
>[Result "1-0"]
>[WhiteElo "?"]
>[BlackElo "?"]
>[FEN "1r4r1/3q1npk/2b1pbnp/Rp1p4/1N1P3P/2PQ1pP1/1K3B2/5B1R w - - 0 1"]
>
>1. Qxg6+ Kxg6 2. Bd3+ Kh5 3. g4+ Kxg4 4. Rg1+ Kf4 5. Bg3+ Kg4 6. Be1+
>Kh3
>7. Bf1+ Kh2 8. Bg3+ Kxg1 9. Ra1 Ra8 10. Rc1 Ra1 11. Kxa1 Qa7+ 12. Kb2
>Qa1+
>13. Kxa1 Ra8+ 14. Na2 Rxa2+ 15. Kxa2 Bg5 16. hxg5 f2 17. Bh3+ f1=Q 18.
>Rxf1# 1-0
>
>I have tried Rebel9 for a few minutes but it didn't find the mate.
>
>The usual killers (quiet moves) here are:
> 9.Ra1
>10.Rc1
>and especially 16.hxg5 f2
>
>Any program?
>
>- Ed -
I tried Gromit and it plays Qxg6 with a score of 0. Of course it can't
see
the mate. The reason for the 0 score is a heuristic that is like 'if
black
has so much more material it should find a variation where the king
isn't
forced to move so often' (anyone else doing things like this? Any
program
playing Qxg6?).
However, if the above position is OK 4. ... Kf4 will be refuted by Bg6
with
mate in 3.

Therefore
4. ...  Kh3
5. Bf1+ Kh2
6. Rg4! e5  (or Ra8 7.Nd3 or Qc7 7.Nd3)
7. Bg3+ Kh1/g1
8. Ra1  Ra8
9. Rd1  Ra1
10.Rxa1 Ra8 (or Qa7, Rb1...)
11.Rd1  Ra1
12.Rxa1 Qa7
13.Rb1  Qa1+
14.Kxa1 Bg5
15.Bh3+ Bc1
16.Rxc1#
I didn't analyze deeply, but it still seems to be a mate in 16 that is
easier for humans than for computers.

Frank



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