Author: Heiner Marxen
Date: 18:48:06 01/25/01
Go up one level in this thread
On January 25, 2001 at 20:41:50, Paul wrote: >On January 25, 2001 at 20:31:55, Heiner Marxen wrote: > >>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 > >Thanks for checking that for me. I couldn't believe it at first!! > >I really hope some other programmer will also try this, coz I don't use >proofnumber search, just 'plain' alpha-beta. Didn't know it was possible. Since the solution line is nearly completely forced, that does not look so impossible to me. I would expect that some programs do find this one, depending on the nature of extensions they do. >Heiner, is it out of reach for Chest? What do you think? > >Paul Yes, that is absolutely out of reach for Chest. The problem is not to find the solution, but to prove all the non-solutions up to a depth of 38. For depth 9 Chest needs 111 seconds, and increasing the depth by one, multiplies the search time by 4. Do the math and be shocked. ;-) Heiner
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