@node ax_prog_cxx_mpi
@unnumberedsec ax_prog_cxx_mpi

@majorheading Synopsis

@smallexample
AX_PROG_CXX_MPI([MPI-WANTED-TEST[, ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]]])
@end smallexample

@majorheading Description

This macro tries to find out how to compile C++ programs that use MPI
(Message Passing Interface), a standard API for parallel process
communication (see http://www-unix.mcs.anl.gov/mpi/).  The macro has to
be used instead of the standard macro AC_PROG_CXX and will replace the
standard variable CXX with the found compiler.

MPI-WANTED-TEST is used to test whether MPI is actually wanted by the
user. If MPI-WANTED_TEST is omitted or if it succeeds, the macro will
try to find out how to use MPI, if it fails, the macro will call
AC_PROG_CC to find a standard C compiler instead.

When MPI is found, ACTION-IF-FOUND will be executed, if MPI is not found
(or MPI-WANTED-TEST fails) ACTION-IF-NOT-FOUND is executed. If
ACTION-IF-FOUND is not set, the macro will define HAVE_MPI.

The following example demonstrates usage of the macro:

@smallexample
  # If --with-mpi=auto is used, try to find MPI, but use standard C compiler if it is not found.
  # If --with-mpi=yes is used, try to find MPI and fail if it isn't found.
  # If --with-mpi=no is used, use a standard C compiler instead.
  AC_ARG_WITH(mpi, [AS_HELP_STRING([--with-mpi],
      [compile with MPI (parallelization) support. If none is found,
      MPI is not used. Default: auto])
  ],,[with_mpi=auto])
@end smallexample

@smallexample
  AX_PROG_CXX_MPI([test x"$with_mpi" != xno],[use_mpi=yes],[
    use_mpi=no
    if test x"$with_mpi" = xyes; then
      AC_MSG_FAILURE([MPI compiler requested, but couldn't use MPI.])
    else
      AC_MSG_WARN([No MPI compiler found, won't use MPI.])
    fi
  ])
@end smallexample

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_prog_cxx_mpi.m4,latest
version of @file{ax_prog_cxx_mpi.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_prog_cxx_mpi.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2010,2011 Olaf Lenz @email{olenz@@icp.uni-stuttgart.de}}

This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.

You should have received a copy of the GNU General Public License along
with this program. If not, see <https://www.gnu.org/licenses/>.

As a special exception, the respective Autoconf Macro's copyright owner
gives unlimited permission to copy, distribute and modify the configure
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