On Apr 21, 2006, at 9:51 AM, Steven W. Orr wrote:
Interesting. I would expect that rotating a sudoku matrix would not
have
any impact in the difficulty of the problem. I remember from my old
numerical analysis course (back before you young whippersnappers were
born) we looked at something called the Hubbard or Hibbard constant
for a
matrix. The deal was that if you multiplied a matrix by its
inverse, then
there was something you would come up with that would tell you how
hard it
was to invert the matrix. Of course you needed the inverse to
calculate it
in the first place...
It's not the asymmetry of the problem that is at fault, but the
asymmetry of the solution. The regexp is a brute force, short-
cutting solver that works from L->R and T->B. That particular
problem simply tickles the worst-case of the regexp, so it's brute
forcing its way through a LOT of wrong solutions before hitting on
the right one.
Chris
--
Chris Dolan, Software Developer, Clotho Advanced Media Inc.
608-294-7900, fax 294-7025, 1435 E Main St, Madison WI 53703
vCard: http://www.chrisdolan.net/ChrisDolan.vcf
Clotho Advanced Media, Inc. - Creators of MediaLandscape Software
(http://www.media-landscape.com/) and partners in the revolutionary
Croquet project (http://www.opencroquet.org/)
