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Subject: Re: Mate in 38.

Author: Heiner Marxen

Date: 17:31:55 01/25/01

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On January 25, 2001 at 19:40:58, Paul wrote:

>On January 24, 2001 at 19:39:52, Dan Andersson wrote:
>
>>[D]1R6/6pK/5p2/4p3/1B1p3n/8/p1p1pp2/1k3b2 w - - 0 1
>>Krabbé (1985)
>
>I just tried this position with my program Pretz, after having unsuccesfully
>grappled with the mate in 16/20 positions by José Antônio Fabiano Mendes
>(I ran out of patience :) and indeed get a mate in 38! It's amazing!
>
>02:17 WM38 09 1. Ba3+ Ka1 2. Bb2+ Kb1 3. Bxd4+ Kc1 4. Be3+ Kd1 5. Rd8+ Ke1 6.
>Bd2+ Kd1 7. Bb4+ Kc1 8. Ba3+ Kb1 9. Rb8+ Ka1 10. Bb2+ Kb1 11. Bxe5+ Kc1 12. Bf4+
>Kd1 13. Rd8+ Ke1 14. Bd2+ Kd1 15. Bb4+ Kc1 16. Ba3+ Kb1 17. Rb8+ Ka1 18. Bb2+
>Kb1 19. Bxf6+ Kc1 20. Bg5+ Kd1 21. Rd8+ Ke1 22. Bd2+ Kd1 23. Bb4+ Kc1 24. Ba3+
>Kb1 25. Rb8+ Ka1 26. Bb2+ Kb1 27. Bxg7+ Kc1 28. Bh6+ Kd1 29. Rd8+ Ke1 30. Bd2+
>Kd1 31. Bb4+ Kc1 32. Ba3+ Kb1 33. Rb8+ Ka1 34. Be7 c1=Q 35. Bf6+ Qb2 36. Rxb2
>e1=Q 37. Rb8+ Qe5 38. Bxe5x
>
>I used 96MB hash and full ply extensions on check and one-rep, and some
>other tricks :) Does this look ok? Has anyone else tried this position?
>
>Groetjes,
>Paul

That looks ok to me.
From a 1993 posting of Dennis Breuker:

An implementation of proof-number search (a kind of conspiracy-number
search) finds the intended solution in 225752 nodes (86 seconds)
on a SPARC-2.

He gives the exact same solution as you do.

Heiner



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