From help-octave-request at bevo dot che dot wisc dot edu  Wed Dec  8 22:42:48 1999
Subject: Constructor for LU: why dgesv?
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Thomas Hoffmann <hoffmann at ehmgs2 dot et dot tu-dresden dot de>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Wed, 8 Dec 1999 22:42:48 -0600 (CST)

On  8-Dec-1999, Thomas Hoffmann <hoffmann at ehmgs2 dot et dot tu-dresden dot de> wrote:

| Excuse my ignorance, but when looking into the ctor for LU
| (e.g. dbleLU.cc), I noticed that octave calls the Fortran subroutine
| dgesv, with a second parameter (NRHS) of 0.
| 
| dgesv calls in turn DGETRF (factorization) and DGETRS (solution). 
| 
| But if one uses NRHS=0, DGETRS only checks some parameters and returns.
| 
| Why does the ctor not call dgetrf directly, when only the
| factorization is necessary?

Good question.  I've fixed my sources so it will just use DGETRF (or
ZGETRF for the complex case) directly instead of calling DGESV
(ZGESV).

Thanks,

jwe



-----------------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.che.wisc.edu/octave/octave.html
How to fund new projects:  http://www.che.wisc.edu/octave/funding.html
Subscription information:  http://www.che.wisc.edu/octave/archive.html
-----------------------------------------------------------------------