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Subject: Re: If you like to solve a mate...

Author: Heiner Marxen

Date: 15:40:38 02/12/01

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On February 12, 2001 at 15:47:55, leonid wrote:

>On February 12, 2001 at 13:11:53, Heiner Marxen wrote:
>
>>On February 12, 2001 at 07:29:02, leonid wrote:
>>
>>>Hi!
>>>
>>>If you like to solve a mate, try this position:
>>>
>>>[D]rQ1Q1rnk/q4qbp/3nQqbB/q1Q1NnNn/5QQ1/b2Q4/1QB3Q1/1K1R3R w - -
>>>
>>>Please, indicate your result.
>>>
>>>In dispite that this position is not that deep and difficult, if your program
>>>don't know how to deel with white crowd it could be in serious trouble. My was
>>>deadly slow in searching for mate even by selective search. Reason - white have
>>>142 initial moves and goes beyond 150 during the search for mate. Good challenge
>>>for every chess program!
>>>
>>>Thanks for responding,
>>>Leonid.
>>
>>Hmmm, not deep?  Not difficult?  "There is no mate in 6" by Chest burns
>>nearly 18 minutes on a K6-3/400 with 50MB hash.  I have started depth=7,
>>but I expect at least 3 hours to complete it, and may be more.
>>At least I can confirm the 142 initial legal moves.
>>
>>Heiner
>
>Thanks, Heiner! You are very close! Mine found mate in 8 by selective. It was
>long. Took 1 min 17 sec.
>
>It is simple since there are not that many moves before the mate and starting
>move (for 8 moves) is checking one.
>
>Leonid.

Phew, that was hard work: after 5.3 hours (K6-3/400, 50MB hash) Chest finds
a unique key for a mate in 7.  Here is a PV:

Ngxf7+ Nxf7 Nxg6+ hxg6 Bxg7+ Nfxg7 Qgxh5+ Nxh5 Qfxf6+ Ngxf6 Qdxf8+ Kh7 Qgxg6#

What about the playing programs?  Normally they are much faster to _find_
a mate.  Did nobody try it, or is this one also hard for them?

Heiner



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