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Subject: Re: Mate in 46

Author: Heiner Marxen

Date: 09:58:53 02/02/01

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On February 02, 2001 at 08:40:06, Enrique Irazoqui wrote:

>On February 02, 2001 at 07:47:52, Heiner Marxen wrote:
>
>>On February 01, 2001 at 17:47:23, Ignacio Santos Crespo wrote:
>>
>>>On January 31, 2001 at 11:25:25, Enrique Irazoqui wrote:
>>>
>>>>On January 31, 2001 at 10:25:50, Heiner Marxen wrote:
>>>>
>>>>>On January 30, 2001 at 17:15:45, Olaf Jenkner wrote:
>>>>>
>>>>>>Perhaps I had in mind this problem what is easily to prove that there is
>>>>>>no shorter mate.
>>>>>>
>>>>>>Pervakow/Sum.  #46
>>>>>>2N5/p4P2/p4RqP/P2krb2/5RNK/2PPBnP1/3P1pP1/5Q2 w - - 1 0
>>>>>
>>>>>Yes, that can be.  Much to my own surprise Chest really proves this
>>>>>as a mate in 46 moves, and needs just 8.2 seconds (K7/600) for it.
>>>>>It gives the following PV:
>>>>>
>>>>> 1. gxf3  Qh5+
>>>>> 2. Kxh5  Bg6+
>>>>> 3. Kxg6  Rg5+
>>>>> 4. Kh7   Rg7+
>>>>> 5. Kh8   Rh7+
>>>>> 6. Kg8   Rh8+
>>>>> 7. Kg7   Rh7+
>>>>> 8. Kf8   Rh8+
>>>>> 9. Ke7   Re8+
>>>>>10. Kd7   Rd8+
>>>>>11. Kc7   Rd7+
>>>>>12. Kb8   Rb7+
>>>>>13. Ka8   Rb8+
>>>>>14. Kxa7  Rb7+
>>>>>15. Kxa6  Ra7+
>>>>>16. Kb5   Rxa5+
>>>>>17. Kb4   Rb5+
>>>>>18. Ka3   Rb3+
>>>>>19. Ka2   Rb2+
>>>>>20. Ka1   Ra2+
>>>>>21. Kb1   Rb2+
>>>>>22. Kc1   Rb1+
>>>>>23. Kc2   Rb2+
>>>>>24. Kd1   Rb1+
>>>>>25. Ke2   Re1+
>>>>>26. Kxf2  Re2+
>>>>>27. Kg1   Rg2+
>>>>>28. Kh1   Rg1+
>>>>>29. Kh2   Rh1+
>>>>>30. Kg2   Rg1+
>>>>>31. Kh3   Rxg3+
>>>>>32. Kh4   Rh3+
>>>>>33. Kg5   Rh5+
>>>>>34. Kg6   Rg5+
>>>>>35. Kh7   Rg7+
>>>>>36. Kh8   Rh7+
>>>>>37. Kg8   Rh8+
>>>>>38. Kg7   Rh7+
>>>>>39. Kg6   Rg7+
>>>>>40. Kh5   Rg5+
>>>>>41. Kh4   Rh5+
>>>>>42. Kg3   Rh3+
>>>>>43. Kf2   Rxf3+
>>>>>44. Ke2   Rf2+
>>>>>45. Nxf2  Ke5
>>>>>46. R4f5#
>>>>>
>>>>>I even had to increase the maximal allowed depth in Chest (formerly 30).
>>>>>Quite an exceptional position!
>>>>>
>>>>>Can the playing programs solve this, also?  I suspect so.
>>>>
>>>>92 plies? You must be kidding. They pick gxf3 instantly with a huge score, but
>>>>no mate. I only tried Deep Fritz, Gambit Tiger and Shredder 5, but I don't think
>>>>any playing program will see it.
>>>>
>>>>Enrique
>>>>
>>>>>Heiner
>>>
>>>On my Pentium 166 after 2... Bg6+, Junior 6 (with 15 Mb. hash) say mate in 42
>>>(6´2")
>>
>>While I'm pleased to hear that a program solved this one,  from the above
>>I believe "mate in 44" would be correct, not "mate in 42".  Can you show
>>us a PV?  I would like to check it.  Someone errs, and I'd like to know who.
>>
>>Heiner
>
>Junior 6 says mate in 42 after 2... Bg6+ in 55 seconds on a P750, 128MB hash,
>see below. I find very impressive that a playing program can see so far ahead
>and so quickly. I'm trying from the initial position with Deep Junior, but after
>14 hours it doesn't see the mate yet.

Hmm, maybe because there are some #7 side variants?  E.g. after 1.gxf3
Qxf6+ Nxf6+  Kc6   Rc4+   Kb7   Nd6+   =*=   f8=Q+  Re8   Qxe8+  Bc8  Qxc8#


>Enrique
>
>[D]2N5/p4P2/p4RbP/P2kr2K/5RN1/2PPBPP1/3P1p2/5Q2 w - - 0 1
>
>Analysis by Junior 6.0:
[snip]
>3.Kxg6! Rg5+ 4.Kh7 Rg7+ 5.Kh8 Rh7+ 6.Kg8 Rh8+ 7.Kg7 Rh7+ 8.Kf8 Rh8+ 9.Ke7 Re8+
>10.Kd7 Rd8+ 11.Kc7 Rd7+ 12.Kb8
>  +-  (#42)   Depth: 44   00:00:55  40825kN
>
>(Irazoqui, Cadaqués 02.02.2001)

The above line follows exactly my PV from above.  Unfortunately Juniors PV
is not complete, so I cannot investigate this further.  But when Chest is
right with #46, then Junior should have said #44 (or larger), but not #42.
That would be a bug, wouldn't it?

OTOH, Chest may have the bug, which is what worries me a bit.
Would you mind to provide the complete line up to the mate move?
You could play it out after the above analysis.  Thanks in advance!

BTW, I spent some 5 minutes for Crafty analysis, but it appears to not solve
it: it did reach depth 14, only.

Heiner



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