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Subject: Re: Unusual Mate in 3

Author: Will Singleton

Date: 09:06:24 03/02/06

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On March 02, 2006 at 00:26:08, Charles Roberson wrote:

>
>  Came across this position by accident browsing chess club web sites.
>  It comes from the Duke University Chess Club. The position is
>  1r5k/4NP1b/7K/8/6R1/8/8/8 w - - 0 1
>
>  Telepath found the mate in 4 but could not find the mate in 3.
>  After some debugging I found out why!!!
>
>  Just before the final ply in the mate in 3, Telepath announced insufficent
>  material which is true. But in this position you can mate with insufficient
>  material.
>
>  It put such a smile on my face, I had to share it.
>
>  Maybe some of you have the same logic flaw in your code.

Nice position.  Rybka falls for it.  Amateur's approach is better, but makes a
slight mistake just after mating. :)

9500 >first: setboard 1r5k/4NP1b/7K/8/6R1/8/8/8 w - - 0 1
9500 >first : go
9500 <first : 3 9993 0 1382 Rg8 Rxg8 Qxg8 Bxg8 Ng6
9500 <first : move g4g8
9656 >first : usermove 9656 >first : b8g8
9671 <first : 3 9995 0 257 Qxg8 Bxg8 Ng6
9671 <first : move f7g8
9687 >first : usermove 9687 >first : h7g8
9687 <first : 1 9997 0 9 Ng6

9687 <first : move e7g6
9687 <first : offer draw
9687 >second: draw
9687 <first : 1-0 {White mates}

GameEnds(31, White mates, 1)
9687 >first : result 1-0 {White mates}
9687 >second: result 1-0 {White mates}

Which is interesting, since it makes the mating move, but offers draw before
announcing mate.  In this case, you can see the draw offer is sent by winboard
to the second engine (glaurung), which ignores it.  So, I assume that it's not
within the rules of chess to accept a draw offer after being mated :)

Will



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