mark, thanks for the tip. if nobody has the CD, i plan on taking a trip to
the library to check it out.
rhonda and i wrote a program to invert a matrix using gauss-jordan with full
pivoting (searching both rows and columns for the optimal pivot point, and
switching both rows and columns).
i learned A LOT from the excersize. for example, let A be a square matrix.
let R(1,2) be a transformation that switches rows 1 and 2. C(1,2) does the
same except with columns.
suppose you want to find the inverse of A, but instead find the inverse of
M = R(1,2)C(2,3)R(1,5)C(11,2)C(2,3)A
then you invert M to get Minv. to get Ainv...
Ainv = C(1,2)R(2,3)C(1,5)R(11,2)R(2,3)Minv
this is the opposite of the "shoes and socks" property, but it makes perfect
sense when you consider how matrix multiplication works.
anyway, i learned lots of little stuff like this that i never knew before.
i plan on writing some routines like this (eigenvalue solver, etc) and make
them into a static library.
pete
On Sun 14 Jan 01, 3:13 PM, Mark Kim said:
> On Sat, 13 Jan 2001, Peter Jay Salzman wrote:
>
> > is there a C equivalent of LAPACK and BLAS (which i understand to be
> > fortran)?
>
> There was an article on Dr. Dobb's Journal (or was it C/C++ Users'
> Journal?... pretty sure it was DDJ) about a couple years ago about a
> numerical C library that outperformed FORTRAN. The author of the article
> (who also authored the library) was trying to show how modern C compilers
> can outperform FORTRAN with a little tweak. I don't exactly remember
> which issue, but it must have been somewhere between late 1997 and early
> 1999. I'm pretty sure the article covered multiple compilers,
> including gcc. Can someone with the DDJ CD do a search for "C and
> FORTRAN"?
>
> -Mark
>
> ---
> Mark K. Kim
> http://www.cbreak.org/mark/
> PGP key available upon request.
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