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Subject: Re: One easy mate to solve.

Author: Heiner Marxen

Date: 17:23:02 11/15/01

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On November 15, 2001 at 12:05:46, Paul wrote:

>On November 15, 2001 at 11:45:39, leonid wrote:
>
>>On November 15, 2001 at 09:44:55, Paul wrote:
>>
>>>On November 15, 2001 at 09:09:08, leonid wrote:
>>>
>>>>[D]2nkN3/2nqN3/2rrbb2/RBqQQqQQ/RBqNPqPQ/2qpqp2/3B4/3K4 w - -
>>>>
>>>>Please indicate your result.
>>>>
>>>>Thanks,
>>>>Leonid.
>>>
>>>Hi Leonid,
>>
>>Hi!
>>
>>>Haha! .. that was a surprise when I saw what Pretz came up with:
>>>
>>>1. Nexc6+ Qcxc6 2. Qgxf6+ Qxf6 3. Qexf6+ Qxf6 4. Qxf6+ Qe7 5. Qxe7+ Nxe7 6.
>>>Nxe6+ Nxe6 7. Ra8+ Nc8 8. Rxc8+ Kxc8 9. Nxd6+ Kd8 10. Ra8+ Qxa8 11. Qxa8+ Qc8
>>>12. Qe8+ Kc7 13. Qexc8+ Kb6 14. Qa5#
>>>
>>>So a mate in 14! I think I must have a bug ...
>>
>>I don't think so. It is mate in 13. Verified it 12 moves deep by brute force to
>>be sure. Easy branching factor. Found mate in 13 by selective. Your, probably,
>>went just one move deper to find its mate. Good result.
>
>Just after I posted my message mine also found a mate in 13 ... I was just too
>quick, but I had to laugh out loud because I know you don't post mates over 13
>moves deep! I thought maybe you had changed your solver.
>
>>I see that you have almost no competition here. Your selective look like to be
>>very effective. I still hope that somebody will come with Chess Master solution
>>to see better your and mine position.
>>
>>What was your time here?
>
>07:28 WM13 13 Nexc6+ Qcxc6 Qgxf6+ Qxf6 Qexf6+ Qxf6 Qxf6+ Ne7 Ra8+ Nxa8 Rxa8+
>Qxa8 Qxa8+ Qcc8 Ba5+ Qcc7 Bxc7+ Qxc7 Nxe6+ Rxe6 Qhd5+ Rd6 Qfxd6+ Qxd6 Qxd6#
>
>So no bug, mine just took the long way home first ...

Hi,

Chest confirms the above: #13 with a unique key move:

PV: Nexc6+ Qcxc6 Qgxf6+ Qxf6 Qhxf6+ Qxf6 Qxf6+ Qe7 Qxe7+ Nxe7 Nxe6+ Nxe6 Ra8+
Nc8 Rxc8+ Kxc8 Nxd6+ Kd8 Nxc4+ Qxd5 Qxd5+ Kc8 Ba6+ Kb8 Qb7#

(K7/600, 30MB hash, 57.2 minutes)
#  1      0.00s                 0kN           0.87          1-         0
#  2      0.00s                 0kN           1.00          1-         0
#  3      0.01s                 0kN [  7.42]  0.92         63-         0
#  4      0.03s [  3.00]        2kN [  3.71]  1.12        190-         0
#  5      0.09s [  3.00]        6kN [  3.29]  1.53        348-         0
#  6      0.25s [  2.78]       18kN [  3.12]  2.03        861-         0
#  7      0.83s [  3.32]       63kN [  3.43]  2.51       2897-         0
#  8      1.98s [  2.39]      155kN [  2.46]  3.12       6827-         0
#  9      6.11s [  3.09]      489kN [  3.17]  3.69      22121-         0
# 10     23.47s [  3.84]     1850kN [  3.78]  3.87     100289-         1
# 11    112.24s [  4.78]     8475kN [  4.58]  4.60     516316-      6868
# 12    501.96s [  4.47]    31935kN [  3.77]  4.53    3036282-   2249851
# 13   3434.74s [  6.84]   208426kN [  6.53]  4.69   20984850-  20198419

>>Mine by brute force took 1 hour and 50 min for 12 moves to say "No". Selective
>>in 13, took 9 seconds.
>
>That's pretty fast ... :)

... but not yet optimal :-))

Cheers,
Heiner



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