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Subject: Re: Very easy mate to solve ...

Author: Heiner Marxen

Date: 08:17:37 05/06/01

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On May 06, 2001 at 06:39:02, leonid wrote:

>On May 05, 2001 at 20:12:25, Heiner Marxen wrote:
>
>>On May 05, 2001 at 18:41:22, Paul wrote:
>>
>>>On May 05, 2001 at 17:47:38, Heiner Marxen wrote:
>>>

>>>>>>[D]3k4/b2r4/4q3/2q3n1/1nnNbqnN/1Q1qpNBQ/r1BPQPp1/qNQRKR1N b - -
>>>>>
>>>>>And this one took a while longer as usual with your creations :), mate in 8:
>>>>>
>>>>>01:22 BM8 07 exf2+ Nxf2 Qaxd4 Bxd3 Qxf2+ Bxf2 Qxf2+ Rxf2 Bxf2+ Qxf2 Bxd3+ Qe3
>>>>>g1=Q+ Nxg1 Qf2#
>>>>>
>>>>>Greetings,
>>>>>Paul

>>Hey, wait a second... while I write this answer, Chest comes up with a mate
>>in 7!  Sorry Paul, that is unexpected for me, too.  Here we go:
>>There are two key moves:  exf2+ and  Qaxd4 (the first two moves of your PV).
>>My PVs (with some more variants) look like:
>
>
>Thanks, Heiner! Very appreciated. I will try to solve this position later in 7.
>Was not even sure if mine will have enough time to do this. Had very bad
>branching factor for this one. Just to give you an idea:
>
>3 moves - 0.1 sec
>             branching factor - 66
>4 moves - 6.59 sec
>                              - 38.6
>5 moves - 4 min 14 sec
>
>And this is where and why I stopped searching by brute froce the last time.
>
>Cheers,
>Leonid.

I don't know, why your effective branching factor is so much worse than
mine, but here is my data for comparison:

depth  seconds speed
#  3      0.05  0.98        110-         0
#  4      1.03  1.05       2162-         0
#  5     21.94  1.21      52287-         0
#  6    470.91  1.51    1467975-        11
#  7   8123.31  1.68   27139229-  18391335

As you can see from the "speed" (estimated hash table speed up) the hash
table is not the main difference this time.  More data for you to compare:
the executed moves per depth to go:

             black      white
mvx  7:        108        133  [108.000  1.231]    mvskip     lvskip
mvx  6:       2191       2615  [ 16.474  1.194]
mvx  5:      61015      60627  [ 23.333  0.994]       1101
mvx  4:    1629538    1488284  [ 26.878  0.913]      37238         10
mvx  3:   30390508   27233557  [ 20.420  0.896]
mvx  2:  409525400   71961657  [ 15.038  0.176]
mvx  1:   84923563          0  [  1.180       ]

The defender (white) manages to nearly always check the defender.
Whenever I start to generate legal moves I look, how often the side to
move is in check:

mg 352166449 W; inchk: 240798413 none 109366513 one   2001523 double
mg  27752191 B; inchk:   4158972 none  23475046 one    118173 double

Of 27.7 million times generated black moves, black is only 4.1 million times
not in check.

I know, that you try check moves first.  When there are multiple check moves,
do you sort them?  There are good checks and bad checks: the goal is to
have more check moves the next time, also.

Just an idea...

Cheers,
Heiner



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