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Subject: Re: Hash Collisions

Author: Dave Gomboc

Date: 01:35:33 02/25/99

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On February 24, 1999 at 10:25:45, Robert Hyatt wrote:

>On February 24, 1999 at 05:34:01, Dave Gomboc wrote:
>
>>On February 23, 1999 at 11:09:40, Robert Hyatt wrote:
>>
>>>On February 23, 1999 at 04:58:30, Dave Gomboc wrote:
>>>
>>>>On February 22, 1999 at 11:14:14, Robert Hyatt wrote:
>>>>
>>>>>I'll try to figure out a way to post my values here if you are interested.
>>>>>64 * 12 isn't horribly big, but when you display them as 64 bit values, they
>>>>>are big. The main issue is how to initialize such an array in a portable
>>>>>way...  IE (BITBOARD ran[12][64] = {{1,2,3},{4,5,6}};  The numbers 1,2,3
>>>>>default to 'int' which is bad.  I don't know what to do for all compilers
>>>>>(IE 123ULL or (BITBOARD) 123)
>>>>
>>>>I don't know of a portable way to do this either.  My Rush Hour
>>>>(www.puzzles.com) software has "#if defined"s like crazy for all of the annoying
>>>>cases, e.g.
>>>>
>>>
>>>
>>>Cute bit of trivia.  Look on the outside of the Rush Hour box, and check
>>>out the names.  One of them dates back to Cray Blitz.  But I won't spoil
>>>the mystery just yet.
>>>
>>>:)
>>
>>Mystery?  On my box, there is only one name!  The box says that Nob Yoshigahara
>>is the inventor of the game.  Perhaps there is a different box in Canada than in
>>the U.S.?  But I doubt it... there's no French on this box, there is just a
>>sticker with French text slapped on top of it, as if it was an afterthought.
>>
>
>
>could have changed.  I have a 'pre-production' version sent to me by Harry
>Nelson, one of the great 'puzzle wizards' on the West Coast.  He wanted me to
>help him with a program to take positions and solve them the shortest way
>possible so they could test 'add on' positions for later release.  I never had
>time...

Oh... well, he can contact me or a few other students at the University of
Alberta (maybe via Jonathan Schaeffer, who gave us the assignment to begin
with.)  We are solving the problems easily, many of them in under a second
apiece.  Jack van Ryswyck's code is the fastest.  It does the whole first deck
of 40 puzzles in 10 seconds flat on a PII-400.

The search space is really small.  We can scan it from the goal states backwards
and build oracle databases.  This gives us maximal distance to solve problems.

I hear that they have a 7x7 version coming out, but I don't think it will be all
that tough for our software either. :-)

Dave Gomboc



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