RE: Autoconf MPI macros

[Daily, Jeff A]

> -----Original Message-----

> From: address@hidden [mailto:autoconf-

> address@hidden On Behalf Of Olaf Lenz

> Sent: Tuesday, May 24, 2011 2:02 AM

> To: address@hidden; address@hidden; Steven G.

> Johnson; Julian C. Cummings

> Subject: Autoconf MPI macros

>

> Hi all!

>

> We are using the GNU autotools and MPI in a number of our projects, and

> we found that the AX_MPI macro from the autoconf macro archive has a few

> shortcomings.

>

> The problem is that AX_MPI starts to do anything only after the standard C

> compiler has been found via AC_PROG_CC. If you want to compile the whole

> package using MPI and simply replace CC with the MPI compiler, this can lead

> to serious trouble. Assume the following case (seen on an IBM AIX machine):

> * gcc is installed

> * the MPI compiler is xlc (the IBM compiler)

>

> If I use AX_MPI in configure.ac, the following will happen in configure:

> * AC_PROG_CC will recognize "gcc" as standard C compiler

> * it will furthermore determine the options that gcc uses to generate

> dependencies

> * then, AX_MPI will recognize the MPI compiler "xlc"

> * CC will be set to "xlc"

>

> When I compile, this means that the compiler tries to generate

> dependencies using the compiler xlc with the options of gcc. In this 
> particular

> case, the option (-MD if I'm not mistaken) caused xlc to output profiling

> information into the .c-file and thus effectively destroyed the C-code.

>

> I believe that the correct way to avoid this problem is a set of new macros

> AX_PROG_{FC,CCCXX}_MPI that are used in configure.ac instead of

> AC_PROG_{CC,FC,CXX}. I have attached the macro AX_PROG_CC_MPI, and a

> git clone of the autoconf macro archive containing the macro can be found at

>

>   https://github.com/olenz/autoconf-archive

>

> Internally, the MPI macro uses the standard macro AC_PROG_CC to find the

> compiler, and directly sets CC to a working MPI version.

>

> I propose to include these macros into the autoconf macro archive, and to

> extend the docs of AX_MPI to point to these macros.

>

> Greetings

>   Olaf

>

> --

> Dr. rer. nat. Olaf Lenz

> Institut für Computerphysik, Pfaffenwaldring 27, D-70569 Stuttgart

> Phone: +49-711-685-63607



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.  We 
use AC_PROG_CC, AC_PROG_F77, and AC_PROG_CXX and pass in a well-known list of 
possible MPI compilers to search for so that CC, F77, and CXX are set and used 
throughout the configure script.  However, we then immediately "unwrap" the MPI 
compilers to determine the standard compilers.  We pass the unwrapped compilers 
to AC_F77_LIBRARY_LDFLAGS.



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.



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.



I've attached hopefully all relevant m4 files we use in our project, Global 
Arrays.

Website: http://www.emsl.pnl.gov/docs/global/

SVN: https://svn.pnl.gov/hpctools
_________________________________________________
Jeff Daily
Scientist
DATA INTENSIVE SCIENTIFIC COMPUTING
Pacific Northwest National Laboratory
902 Battelle Boulevard
P.O. Box 999, MSIN K7-90
Richland, WA  99352 USA
Tel:  509-372-6548
Fax: 509-372-4720
address@hidden
www.pnnl.gov

ga_f77_library_ldflags.m4
Description: ga_f77_library_ldflags.m4

ga_mpi_unwrap.m4
Description: ga_mpi_unwrap.m4

ga_mpicc.m4
Description: ga_mpicc.m4

ga_mpicxx.m4
Description: ga_mpicxx.m4

ga_mpif77.m4
Description: ga_mpif77.m4