Re: [Plplot-devel] Recently spotted issues with libnn and libcsa (and libpthreads)

[Alan W. I. <ir...@be...>]

On 2003-09-24 03:00+0100 Jo=E3o Cardoso wrote:
> On Tuesday 23 September 2003 20:47, Alan W. Irwin wrote:
> |  I just finished a large least-squares fit using SVD for my
> | research, and because of the licensing nastiness with Numerical Recipes=
 I
> | chose to use the dgesdd routine from the lapack library instead.
>
> This is definitively an option (shouldn't it be dgesvd?).

Both dgesvd and dgesdd compute the SVD, but the latter one has been
developed more recently and uses something called the divide-and-conquor
algorithm.  I have no clue what that means, but since they went out of thei=
r
way to develop it later, I tried dgesdd first, and it worked very well.

>
> |  I suggest
> | you should do the same. A complication is to find a fool-proof
> | cross-platform way to interface from C to that fortran routine.
>
> Haven't the gsc (Gnu  Scientific Library) guys converted dgesvd to C? hum=
m,
> they have implemented their own SVD, based on "the Golub-Reinsch SVD
> algorithm", which I think is the same algorithm that NR uses (at least th=
eir
> names are in the NR references).
> But requiring the huge gsc library or a fortran compiler is an overkill..=
=2E

gsl (which I think is what you were referring to by gsc) is not appropriate
for our LGPLed PLplot because gsl is licensed under GPL.  On the other hand=
,
look up cfortran at http://packages.debian.org/unstable/devel/cfortran.html
and on google.  All it is is a convenient header to make life easy for
calling fortran libraries from C or C libraries from fortran.  No fortran
compiler is involved.

Alan
__________________________
Alan W. Irwin
email: ir...@be...
phone: 250-727-2902

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the PLplot scientific plotting software
package (plplot.org), the Yorick front-end to PLplot (yplot.sf.net), the
Loads of Linux Links project (loll.sf.net), and the Linux Brochure Project
(lbproject.sf.net).
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