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Subject: Re: Mate that every program will solve...

Author: Paul

Date: 15:17:43 04/17/01

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On April 17, 2001 at 17:46:51, Heiner Marxen wrote:

>[D]R3Q3/5bPq/1rR5/2p2rnk/1Q3B2/4Nn2/1PBb1NQ1/2K5 w - -
>and Chest does not find a mate in 5, here.  Here is its refutation table:
>refu  1: Qxd2    Rxc6    [  4-]
>solu          1: Bxe8    [  1+]
>solu          2: Nxd2    [  1+]
>solu         11: Nd4     [  1+]
>solu         12: Ne5     [  2+]
>solu         13: Ne1     [  1+]
>solu         14: Ng1     [  1+]
>solu         15: Qxg7    [  1+]
>solu         16: Ra6     [  1+]
>refu  2: Kd1     Rxc6    [  4-]
>solu          3: Bxe8    [  1+]
>solu          4: cxb4    [  1+]
>solu          5: Bxb4    [  1+]
>solu          6: Rxb4    [  1+]
>solu         17: Ne4     [  1+]
>solu         18: Rd5     [  1+]
>solu         19: Nh3     [  1+]
>solu         20: Ra6     [  1+]
>refu  3: Kb1     Rxc6    [  4-]
>solu          7: Bxe8    [  1+]
>solu          8: cxb4    [  1+]
>solu          9: Bxb4    [  1+]
>solu         10: Rxb4    [  1+]
>solu         21: Ne4     [  1+]
>solu         22: Ra6     [  1+]
>solu         23: Qxg7    [  1+]
>
>Hope this helps you to pin this down further.
>
>If you still find a short enough mate, here, please post it, and I will
>answer with the variant Chest uses to refute it.  In the end we will see
>who errs, when the mates become short enough that we poor humans see it
>ourselves.
>
>Heiner

Excuse me if I mingle into this conversation, but this is a point where Pretz
also goes wrong. After Qxd2, it thinks that Rxf4 is the best defense, thereby
overlooking Rxc6:

Qxd2 Rxf4 Qxf7+ Nxf7 Bg6+ Qxg6 Qxg6+ Kh4 Ng2#

With hashtables switched off it does find Rxc6:

Qxd2 Rxc6 Qg4+ Kg6 Qxf5+ Kh5 Qexf7+ Rg6 Qg4+ Kh6 Nf5#

Now, what to do next? Any hints Heiner, Tim? :)

Paul



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