Add MPI and METIS support, neither is enabled by default

For future requirements

configure.ac

@@ -45,6 +45,59 @@ LT_INIT
 AX_COMPILER_VENDOR
 AX_COMPILER_VERSION
 
+# Check for MPI. Need to do this before characterising the compiler (C99 mode),
+# as this changes the compiler.
+# We should consider using AX_PROG_CC_MPI to replace AC_PROG_CC when compiling
+# whole applications. There are issues with mixing compilers when using this
+# macro. See
+# http://lists.gnu.org/archive/html/autoconf-archive-maintainers/2011-05/msg00004.html.
+AC_ARG_ENABLE([mpi],
+    [AS_HELP_STRING([--enable-mpi],
+      [Compile with functionality for distributed-memory parallelism using MPI @<:@default=yes@:>@]
+    )],
+    [enable_mpi="$enableval"],
+    [enable_mpi="no"]
+)
+if test "$enable_mpi" = "yes"; then
+    AX_MPI([CC="$MPICC" AC_DEFINE(HAVE_MPI, 1, [Define if you have the MPI library.]) ])
+
+    # Various MPI implementations require additional libraries when also using
+    # threads. Use mpirun (on PATH) as that seems to be only command with
+    # version flag.
+    AC_PATH_PROG([MPIRUN],[mpirun],[notfound])
+    if test "$MPIRUN" = "notfound"; then
+       AC_MSG_WARN([Cannot find mpirun command on PATH, thread support may not be correct])
+    else
+       # Special options we know about.
+       # Intel: -mt_mpi
+       # PLATFORM: -lmtmpi
+       # OpenMPI: nothing, but library should be built correctly.
+       # Set MPI_THREAD_LIBS and add to linker commands as necessary.
+       AC_MSG_CHECKING([MPI threads options])
+       version=`$MPIRUN -version 2>&1`
+       case "$version" in
+         *Intel*MPI*)
+            MPI_THREAD_LIBS="-mt_mpi"
+            AC_MSG_RESULT([Intel MPI])
+         ;;
+         *Platform*)
+            MPI_THREAD_LIBS="-lmtmpi"
+            AC_MSG_RESULT([PLATFORM MPI])
+         ;;
+         *"Open MPI"*)
+            MPI_THREAD_LIBS=""
+            AC_MSG_RESULT([Open MPI])
+         ;;
+         *)
+            MPI_THREAD_LIBS=""
+            AC_MSG_RESULT([unknown])
+         ;;
+       esac
+       AC_SUBST([MPI_THREAD_LIBS])
+    fi
+fi
+AM_CONDITIONAL([HAVEMPI],[test -n "$MPICC"])
+
 # Need C99 and inline support.
 AC_PROG_CC_C99
 AC_C_INLINE
@@ -125,6 +178,29 @@ else
    AC_DEFINE(HAVE_OPENMP,1,[Define if OpenMP is enabled])
 fi
 
+# Check for metis. Note AX_LIB_METIS exists, but cannot be configured
+# to be default off (i.e. given no option it tries to locate METIS), so we
+# don't use that.
+AC_ARG_WITH([metis],
+    [AS_HELP_STRING([--with-metis=PATH],
+       [prefix where the metis library is installed @<:@default=yes@:>@]
+    )],
+    [],
+    [with_metis="no"]
+)
+if test "x$with_metis" != "xno"; then
+   if test "x$with_metis" != "xyes" -a "x$with_metis" != "x"; then
+      METIS_LIBS="-L$with_metis -lmetis"
+   else
+      METIS_LIBS="-lmetis"
+   fi
+   AC_CHECK_LIB([metis],[METIS_PartGraphKway],
+      AC_DEFINE([HAVE_METIS],1,[The metis library appears to be present.]),
+      AC_MSG_ERROR(something is wrong with the metis library!),$METIS_LIBS)
+fi
+AC_SUBST([METIS_LIBS])
+AM_CONDITIONAL([HAVEMETIS],[test -n "$METIS_LIBS"])
+
 # Check for timing functions needed by cycle.h
 AC_C_INLINE
 AC_HEADER_TIME
@@ -164,7 +240,9 @@ AC_MSG_RESULT([
      vendor: $ax_cv_c_compiler_vendor
     version: $ax_cv_c_compiler_version
       flags: $CFLAGS
+   MPI enabled: $enable_mpi
    OpenMP enabled: $enable_openmp
+   Metis enabled: $with_metis
 ])
 
 # generate output.