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Subject: Re: Mate the Royal Couple

Author: Heiner Marxen

Date: 08:46:50 11/15/98

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On November 14, 1998 at 10:37:55, Hans Havermann wrote:

>Valentin Albillo, more than a year ago, posted his "unsolved"
>3qk3/8/8/8/8/8/PPPPPPPP/RNBQKBNR w KQ - (Test #91:
><>). Computationally intensive,
>Albillo conjectured "it's a mate in 12". A number of chess engines had a go at
>it, but the attempts are old and seem dated. I wonder if this problem has since
>been solved.

This problem is really hard to solve.  According to my problem solving
program this is most probably not solvable in 9 moves (or less).
[ "most probably" because I accidentally turned castling off ]
That computation took 4.5 hours on a fast machine.  Trying to solve
(or disprove) a mate in ten would take 15x that time.  I didn't try,
and now I don't have access to that fast/big box anymore.

>I thought I should let MacChess (5.0b3) try this on my 300 MHz G3. After 56
>hours, toward the end of 13-ply, MacChess came up with:
> 1. e4 Qd4
> 2. Bb5+ Ke7
> 3. Qg4 Qe5
> 4. Qd7+ Kf8
> 5. d3 Qh5
> 6. Bf4 Qf7

Well, starting from here, I can confirm, that 1.Bh6+ is a mate in 6,
that there is no faster way to force mate, nor any other way to mate in 6.
I'm working on more, but don't hold your breath.

> 7. Bh6+ Kg8
> 8. Bc4 Kh7
> 9. Qxf7+ Kxh6
>Despite the program's move-extenders (which caused my analysis to go 93 plies
>deep on some line!), it couldn't see the follow-up (because, I guess, "g3" is a
>non-trivial move and does not engage the move-extender):
>10. g3 Kg5
>11. Qg7+ Kh5
>12. Bf7#
>Anyways, I do not pretend this (necessarily) "solves" the problem. But there >are
>people out there with faster computers and better programs than mine. Anyone?

Yes, I'm curious, too.

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