Re: Autoconf MPI macros

[Olaf Lenz]

Hi!

On 05/24/2011 06:16 PM, Daily, Jeff A wrote:
> There are additional shortcomings that we noticed while trying to
> use MPI compilers with autotools.  Specifically to autoconf, on some
>  systems the MPI compilers produce incorrect results for the 
> AC_F77_LIBRARY_LDFLAGS test.

The GA_F77_LIBRARY_LDFLAGS macro only cares for the special case of the
Sun compiler. Maybe this is something that should be considered for
inclusion into autoconf itself?

> Further, if you're using libtool, you must pass the unwrapped 
> compilers to libtool because libtool unfortunately compares against 
> compiler names.  Worse yet, after libtool is finished with its tests,
> we have to substitute back in the MPI compilers which is a hack, at
> best.

Now I see why we don't use libtool at the moment. ;-o

I think the core of the problem is that MPI uses the "MPI compilers" in
the first place, instead of handling MPI as the library that it is in
most cases. However, we won't be able to solve this problem in this
list, I'm afraid.

> Of course, if the user passes the MPI include paths, library paths, 
> and MPI libraries manually then there is no issue since a standard 
> compiler is then used throughout.  We only have issues trying to use
>  the MPI compilers.  Our default is to use the compiler wrappers, but
>  we allow the user to pass arguments to our --with-mpi option which 
> then disables the use of the MPI compilers.

Now I wonder which of the macros are generic enough to be used for the
autoconf macro archive. If I understand your macros correctly, the
GA_MPI{CC,CXX,F77} macros try to find a compiler, but they don't
actually check whether an MPI program can be compiled, nor whether the
MPI header is available. If I would extend the list of MPI compilers in
the AC_PROG_CC_MPI macro to match the list in your macros, it should be
more or less equivalent to your macros, shouldn't it?
In any case, I have extended the "AX_PROG_CC_MPI" macro accordingly.

Then there is the MPI unwrap macro. I believe that it might be useful to
people that want to use libtool and build shared libraries. One might
consider the macro for inclusion to the autoconf macro archive.

Cheers
  Olaf


-- 
Dr. rer. nat. Olaf Lenz
Institut für Computerphysik, Pfaffenwaldring 27, D-70569 Stuttgart
Phone: +49-711-685-63607

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