Add run-time test of MPI launcher.

configure

@@ -26632,10 +26632,72 @@ fi
   test -n "$MPI_LAUNCH" && break
 done
-   if test x$MPI_LAUNCH = x; then :
+test -n "$MPI_LAUNCH" || MPI_LAUNCH="true"
+
+   if test x"$cross_compiling" = xno; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking if $MPI_LAUNCH works" >&5
+$as_echo_n "checking if $MPI_LAUNCH works... " >&6; }
+      saved_CFLAGS=$CFLAGS
+      saved_LIBS=$LIBS
+      CFLAGS="$CFLAGS $MPI_C_INCLUDE"
+      LIBS="$LIBS $MPI_C_LIB"
+      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <mpi.h>
+#define xmpi(ret)           \\
+  do {                      \\
+    if (ret != MPI_SUCCESS) \\
+      exit(EXIT_FAILURE);   \\
+  } while (0)
+
+int
+main(int argc, char **argv)
+{
+  xmpi(MPI_Init(&argc, &argv));
+  char *numarg = argv[1];
+  int cmdnum = atoi(numarg);
+  int procnum = 1;
+  xmpi(MPI_Allreduce(MPI_IN_PLACE, &procnum, 1, MPI_INT, MPI_SUM,
+                     MPI_COMM_WORLD));
+  xmpi(MPI_Finalize());
+  return (procnum == cmdnum)?EXIT_SUCCESS:EXIT_FAILURE;
+}
+
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  if $MPI_LAUNCH -n 4 ./conftest$EXEEXT 4; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+             { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "mpirun doesn't work
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+else
+  { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error $? "Cannot compile simple MPI program
+See \`config.log' for more details" "$LINENO" 5; }
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+      CFLAGS=$saved_CFLAGS
+      LIBS=$saved_LIBS
 fi
+   if test "x$MPI_LAUNCH" = xtrue; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: MPI launch command unavailable" >&5
+$as_echo "$as_me: WARNING: MPI launch command unavailable" >&2;}
+fi
+
 pkg_failed=no
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for YAXT" >&5

configure.ac

@@ -94,8 +94,49 @@ AS_IF([test x"${enable_mpi}" = x"yes"],
 HAVE_PARALLEL_NC4=0
 AS_IF([test x"$USE_MPI" = xyes],
   [AC_DEFINE([USE_MPI],[1],[parallel I/O requested and available])
-   AC_PATH_PROGS([MPI_LAUNCH],[mpirun mpiexec],[])
-   AS_IF([test x$MPI_LAUNCH = x],[])
+   AC_PATH_PROGS([MPI_LAUNCH],[mpirun mpiexec],[true])
+   AS_IF([test x"$cross_compiling" = xno],
+     [AC_MSG_CHECKING([if $MPI_LAUNCH works])
+      saved_CFLAGS=$CFLAGS
+      saved_LIBS=$LIBS
+      CFLAGS="$CFLAGS $MPI_C_INCLUDE"
+      LIBS="$LIBS $MPI_C_LIB"
+      AC_LINK_IFELSE([AC_LANG_SOURCE([
+@%:@include <stdio.h>
+@%:@include <stdlib.h>
+
+@%:@include <mpi.h>
+
+@%:@define xmpi(ret)           \\
+  do {                      \\
+    if (ret != MPI_SUCCESS) \\
+      exit(EXIT_FAILURE);   \\
+  } while (0)
+
+int
+main(int argc, char **argv)
+{
+  xmpi(MPI_Init(&argc, &argv));
+  char *numarg = argv@<:@1@:>@;
+  int cmdnum = atoi(numarg);
+  int procnum = 1;
+  xmpi(MPI_Allreduce(MPI_IN_PLACE, &procnum, 1, MPI_INT, MPI_SUM,
+                     MPI_COMM_WORLD));
+  xmpi(MPI_Finalize());
+  return (procnum == cmdnum)?EXIT_SUCCESS:EXIT_FAILURE;
+}
+])],
+         [AS_IF([$MPI_LAUNCH -n 4 ./conftest$EXEEXT 4],
+            [AC_MSG_RESULT([yes])],
+            [AC_MSG_RESULT([no])
+             AC_MSG_FAILURE([mpirun doesn't work])])],
+         [AC_MSG_FAILURE([Cannot compile simple MPI program])])
+      CFLAGS=$saved_CFLAGS
+      LIBS=$saved_LIBS
+     ])
+   AS_IF([test "x$MPI_LAUNCH" = xtrue],
+     [AC_MSG_WARN([MPI launch command unavailable])])
+
    PKG_CHECK_MODULES([YAXT],[yaxt],
      [AC_DEFINE([HAVE_YAXT],,[yaxt library is available])],
      [AC_MSG_FAILURE([Required yaxt library unavailable.])])