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

Author: Uri Blass

Date: 13:08:25 01/21/01

Go up one level in this thread


On January 21, 2001 at 15:22:30, Heiner Marxen wrote:

>On January 21, 2001 at 14:13:30, leonid wrote:
>
>>On January 21, 2001 at 13:44:00, Heiner Marxen wrote:
>>
>>>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 :-)
>>
>>And what the monitor you have? 21 inch?
>>
>>The last time, around 3 months ago, I bought my last 17 inch. Very cheap and
>>very good. My next dream is new computer. I need it for my programming.
>
>It is a 15.1 inch TFT screen.  It had to fit into this tiny room, where
>my computer is placed.  I am very satisfied with it, but it is not cheap.
>
>>>>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
>>
>>Pretty good branching factor!
>
>Yes, and here is the next line:
># 11   3686.85  2.90   20110217-  11363105
>
>Chest does not find any mate in 11.
>
>>>>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.
>>
>>For 11 moves I don't know. My solved it by selective only at 12. Actually, this
>>position is more that strange. Solution was found by the most easy level in
>>selective search. Because of very good for me branching factor, I expected it
>>will be instant. It was not so. It took 2 seconds.
>>
>>Leonid.
>
>Fine, so I stop this, now.  Looks like there is no shorter mate,
>which is not surprising for a position like this one.
>
>I just asked crafty 17.7 for a depth=1 analysis, and even after 3 minutes
>I still see no output ;-)  Obviously the quiescence search is exploding.
>
>Can you give some PV for the forced #12 line?  Just curious.
>
>Heiner

1.Qxa7+ Qxa7 2.Qxa7+ Kxa7 3.Qgxb7+ Qdxb7(to prevent the threat Qxb8+)
4.Qexc5+ Q4xc5(Ka8 Qxb8+ and Qb7 is pinned) 5.Qxb8+ Qcxb8(Qbxb8 Bxb8+ mate in 2)
6.Qxc5+ Q7b6(Q2b6 let Ra2+) and I guess that now chest has no problem to see
that 7.Bxb8+ is a mate in 6.

Uri



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