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Subject: Re: Mate in 46

Author: Dann Corbit

Date: 14:54:13 01/31/01

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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
>>[D]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.

4 seconds on my machine.  I made this change:

#ifndef MAX_ANA_DEPTH
# define MAX_ANA_DEPTH  ((255 >> 2)-1)      /* CF: maximum depth (a 2 moves) of
analysis */
#endif

can MAX_ANA_DEPTH be increased further without major surgery?

2N5/p4P2/p4RqP/P2krb2/5RNK/2PPBnP1/3P1pP1/5Q2 w - - acn 571764; acs 4; bm gxf3;
ce 32676; dm 46; pv gxf3 Qh5+ Kxh5 Bg6+ Kxg6 Rg5+ Kh7 Rg7+ Kh8 Rh7+ Kg8 Rh8+ Kg7
Rh7+ Kf8 Rh8+ Ke7 Re8+ Kd7 Rd8+ Kc7 Rd7+ Kb8 Rb7+ Ka8 Rb8+ Kxa7 Rb7+ Kxa6 Ra7+
Kb5 Rxa5+ Kb4 Rb5+ Ka3 Rb3+ Ka2 Rb2+ Ka1 Ra2+ Kb1 Rb2+ Kc1 Rb1+ Kc2 Rb2+ Kd1
Rb1+ Ke2 Re1+ Kxf2 Re2+ Kg1 Rg2+ Kh1 Rg1+ Kh2 Rh1+ Kg2 Rg1+ Kh3 Rxg3+ Kh4 Rh3+
Kg5 Rh5+ Kg6 Rg5+ Kh7 Rg7+ Kh8 Rh7+ Kg8 Rh8+ Kg7 Rh7+ Kg6 Rg7+ Kh5 Rg5+ Kh4 Rh5+
Kg3 Rh3+ Kf2 Rxf3+ Ke2 Rxe3+ Nxe3+ Ke5 d4#;



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