Author: Stuart Cracraft
Date: 23:53:16 09/29/04
The null move killed, win-at-chess 141, has itself
finally been killed, vanquished with the help of
two board contributors whose combined suggestion
led to a 17-fold reduction in time-to-solve.
This posting announces those winners. First the
stats!
Now solved in 5.49 seconds on a P3 @ 1ghz it would be
solved in under 2 seconds on more modern equipment.
Formerly it took 95 seconds to solve.
That's good enough for me. And it's good enough to win
the $50 contest posed recently since it broke the
10-second-and-under-barrieras posed in the contest
posting.
The search:
Alpha=-1332 Beta=-531 Maxdepth=9999999 MaxTime=99999
1/ 9 g2f1 0.00 -953 511 g2f1 f4d5
g2f1 f4d5
2/ 9 g2f1 0.01 -953 884
g2f1 f4d5 c1g5
3/12 g2f1 0.06 -953 11929
g2f1 f4d5 c1g5 d5f6
4/16 g2f1 0.39 -953 72781
g2f1 f4d5 b3d5 c6d5 f1g2 d6e7
5/24> g2f1 3.83 -552 978925
g2f1 b5b4 b3a4 f4d5 f6g5 d5e7
5/25 c1f4 5.49 2260 1420038 c1f4 d6f4 h4h5 g6h5 h1h5 f4h6 h5h6 c7g3 g2g3 d7d
6
c1f4 d6f4 h4h5 g6h5 h1h5 f4h6 h5h6 c7g3 g2g3 d7d
6
6/25 c1f4 6.06 2260 1519145
c1f4 d6f4 h4h5 g6h5 h1h5 f4h6 h5h6 c7g3 g2g3 d7d
6
And with it the announcement -- because of the contribution
of Will Singleton in indicating that null move should be
avoided before leaves in the main search (and the sense
of a comparison in an old commented out section of the
code associated with disabled null move verification having been
intended to do what Will suggested but having been miscoded
by me and then #ifdefed out months ago) and Uri Blass'
comments about my recaptures being too free and easy,
the program went from a total of 95 seconds
for wac 141 to 5.49 after these two suggestions were
implemented.
So Will and Uri are the winners, if they wish to accept,
of the divided $50 prize. Because Will's contribution was
more significant but less work for him and Uri's contribution
was less significant but with more work for him, but in either
case without the change from the other's suggestion the result
would not have been as dramatic getting down to <= 10 seconds
as stated in the earlier contest challenge a day or two ago,
the award has been divided in half for the 2 winners.
Will and Uri are welcome to send me, and only if they wish
to collect, their postal mail addresses, to cracraft@cox.net
and a check for $25 will be sent out to each.
In the future, more contests will be held like this whenever
I run into a huge roadblock but I see none looming presently,
including a rather unusual one that I am not ready to announce.
Thanks everybody for the help on 141 -- and thanks to Will
Singleton and Uri Blass.
Stuart
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