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Constructor for LU: why dgesv?


From: John W. Eaton
Subject: Constructor for LU: why dgesv?
Date: Wed, 8 Dec 1999 22:42:48 -0600 (CST)

On  8-Dec-1999, Thomas Hoffmann <address@hidden> 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



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