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Subject: Re: If you want solve one mate...

Author: Heiner Marxen

Date: 10:44:00 01/21/01

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On January 21, 2001 at 13:16:22, leonid wrote:

>On January 21, 2001 at 12:43:34, Heiner Marxen wrote:
>
>>On January 21, 2001 at 11:56:09, leonid wrote:
>>
>>>Hi!
>>>
>>>This mate position is very handy when you want to check the limits in your
>>>program. It is amusing also. Number of legal moves for both sides is slightly
>>>over one hundred.
>>>
>>> knq3q1/rq1q1qbQ/Qq2Q3/1Qn1Q2B/Q1qN1Q1r/4K1B1/1q4QR/1N1q3Q white to go.
>>
>>A hint to you, Leonid:  if you like to see a diagram for the notation above:
>>(1) Stick a [D] directly before the FEN string,
>>(2) append (blank seperated) colour to move, i.e. b or w
>>(3) append (blank seperated) castling rights: - for nothing, KQkq or part
>>    of it for white/black king side/queen side
>>(4) append (blank seperated) e.p. info: - for "no e.p. possible"
>>You can look up the details in the FEN standard, part of the PGN standard.
>>Look at the line below, which I typed in, and see the diagram, provided not
>>by me, but by the CCC web server, which recognizes the [D] and FEN after it,
>>and inserts the graphics.  You can do that also.
>
>Thanks! Will try to use it the next time.
>
>Leonid.
>
>
>>[D]knq3q1/rq1q1qbQ/Qq2Q3/1Qn1Q2B/Q1qN1Q1r/4K1B1/1q4QR/1N1q3Q w - -
>>
>>Chest says "no mate in 9" (216 seconds, K7/600 335MB hash).
>>I will ask for more depth...
>
>Are there no mistake? You have really 335Mb hash?

Yes!  :-)
I bought 512 MB.  Was a bit expensive, but my monitor costs even more.
And on work I have seen what 512MB can do to big Chest jobs, so I really
wanted to have so much memory.  I like it :-)

>216 sec for 9 moves like very good. I went, by brute force, only up to 7 moves.
>It was already 2 min. 19 sec. But for this position, which look very heavy,
>branching factor was very normal. Like what you can expect from usual forced
>mate position.
>
>4 moves - 0.77 sec
>               branching factor 5.8
>5 moves - 4.39 sec
>                                5.3
>6 moves - 23.02 sec
>                                6.1
>7 moves - 2 min 19 sec

Yes, black has also 9 queens, and whites king is exposed.  If white does
anything not really forcing, black will start to force, or even mate.
Therefore the search trees can be small in many branches.  In 17% of all
considered cases, black mates white!  (yes, Chest tries that sometimes)

Here are my numbers:

#  1      0.00  0.87          1-         0
#  2      0.01  1.00          1-         0
#  3      0.03  0.96        107-         0
#  4      0.19  1.04        819-         0
#  5      0.87  1.23       4167-         0
#  6      3.73  1.48      17787-         0
#  7     14.90  1.79      72503-         0
#  8     56.43  2.17     290160-         0
#  9    213.00  2.57    1142162-         0
# 10    831.85  2.90    4544295-     16385
(depth  seconds speed   node in   node out)

>Leonid.
>
>>Heiner
>>
>>>If you will solve, it will be nice if you will indicate your result.


Is there any forced solution, at all?  Depth=11 will take around an hour,
and I will not go much further, if there is no real chance.

Heiner



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