[GRASS-dev] BLAS/LAPACK detection (was: configure fails)

[Glynn Clements]

Brad Douglas wrote:

> > I see that this is related to Brad's and Markus' changes of today. Does
> > this mean that the fortran compiler in mingw is not sufficient ? Or is
> > this an error in the configure file ? Also, do I absolutely need a fortran
> > complier ?
> > For what ?
> 
> For now, no, you don't need a working Fortran compiler.
> 
> Fortran is required for certain versions of BLAS/LAPACK.  There are
> other equivalents that may be more forgiving like ATLAS, PhiPACK,
> CBLAS/CLAPACK.
> 
> My changes were meant to expand BLAS/LAPACK detection.  It should detect
> traditional BLAS/LAPACK, CBLAS/CLAPACK, ATLAS, PhiPACK, and Apple's
> compatible vector library.

Unfortunately, it reduces detection rather than expanding it.

The following changes need to be made:

1. --with-gfortran should default to "no". The only things which
should default to yes are those which most users will have and want.

We adopted this behaviour because, otherwise, users would fail to
notice the warning about e.g. libpng not being found and then posted
to the list asking "where is the PNG driver?"

Features that most users won't care about don't need this treatment. 
It just means that the user has to go back and re-run configure with
an extra --without-* switch.

2. Failure to locate cblas.h and/or clapack.h must not cause a fatal
configure error.

I don't have these files, but --with-blas and --with-lapack worked
fine until the latest changes.

LOC_CHECK_INCLUDES() can take a fourth argument comprising code to be
executed if the check fails. If no such argument is given, a fatal
error is generated.

3. --with-g77 should not be required to detect g2c.h/f2c.h or -lg2c.

Again, I never needed this before.

I'm not actually compiling any Fortran code, just C code which uses a
library written in Fortran; this doesn't require a Fortran compiler.

It may require some support files (header, library) which are normally
installed with the Fortran compiler, but those can (and should) be
detected as with any header or library. There's no need to check for a
Fortran compiler unless you're actually going to be compiling Fortran
code.

For now, I've reverted my local configure[.in] to the previous version
to eliminate the regressions. Unless some other fix is found, I intend
to commit the reversions.

-- 
Glynn Clements <glynn at gclements.plus.com>