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Subject: Re: One very easy mate to solve.

Author: Heiner Marxen

Date: 07:30:17 05/24/01

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On May 23, 2001 at 22:45:11, leonid wrote:

>On May 23, 2001 at 19:35:00, Heiner Marxen wrote:
>
>>On May 23, 2001 at 15:37:07, leonid wrote:
>>
>>>[D]RrqkqrR1/qPNbNPq1/BnqBqnB1/bqQQQqb1/Q2K2Q1/3B4/8/8 w - -
>>
>>This one has an even smaller effective branching factor.  It has the same
>>set of solution moves, but it is a mate in 12:
>
>Here I was not sure where is the mate. Your finding is useful. 10 moves took
>already 6 hours and 28 minutes to say that no mate exist. For 11 moves it could
>be expected as 50 hours. Branching factor started to grow for my program just
>after 7 moves. It was between 4 and 5 move - 5.4. Mate was found for sure in 13
>moves by selective. Took 7 sec. Big number of possible solutions make this
>position quit useful for possible logic verification.
>
>Cheers,
>Leonid.

Hmm, Chest does not suffer from a bad branching factor, quite the opposite:

depth  seconds speed (= hash table speed up)
#  1      0.00  0.96          1-         0
#  2      0.00  1.00          1-         0
#  3      0.02  0.93         81-         0
#  4      0.09  1.02        507-         0
#  5      0.32  1.24       1941-         0
#  6      0.92  2.75       5583-         0
#  7      2.73  4.82      16205-         0
#  8      9.95  5.71      58319-         0
#  9     19.95 11.80     115465-         0
# 10     39.25 17.14     227722-         0
# 11     86.12 18.24     506580-         0
# 12    163.57 13.09     978074-         0

Looks like the hash table kicks in quite nicely, as seen from the speed factor.
It reduces the effective branching factor down to around 2!

Have a nice day!
Heiner



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