Let configure define USE_MPI in case MPI is available.

configure

@@ -24005,14 +24005,13 @@ else
   enable_mpi=no
 fi
-if test "${enable_mpi}" = "yes"; then :
-  if test "${host_os%???}" = "aix"; then :
-  replace_cc="mpicc"
-else
-  replace_cc="mpcc_r"
+if test x"${enable_mpi}" = x"yes"; then :
+  USE_MPI=yes
 fi
-else
-  replace_cc=$CC
+if test x"$USE_MPI" = xyes; then :
+
+$as_echo "#define USE_MPI 1" >>confdefs.h
+
 fi
 #  ----------------------------------------------------------------------
 #  Create the Fortran Interface via iso_c_binding module (Fortran 2003 Standard)
@@ -24398,10 +24397,6 @@ fi
-if test "x${replace_cc}" != "x"; then :
-  CC=$replace_cc
-fi
-
 ac_config_files="$ac_config_files Makefile src/Makefile interfaces/Makefile app/Makefile tests/Makefile examples/Makefile cdi.settings"
 cat >confcache <<\_ACEOF

configure.ac

@@ -107,11 +107,10 @@ ACX_OPTIONS
 #  ----------------------------------------------------------------------
 # Compile with MPI support
 AC_ARG_ENABLE(mpi,AS_HELP_STRING([--enable-mpi],[Compile with MPI compiler [default=no]]),enable_mpi=${enableval},enable_mpi=no)
-AS_IF([test "${enable_mpi}" = "yes"],
-      [AS_IF([test "${host_os%???}" = "aix"],
-             [replace_cc="mpicc"],
-             [replace_cc="mpcc_r"])],
-      [replace_cc=$CC])
+AS_IF([test x"${enable_mpi}" = x"yes"],
+      [USE_MPI=yes])
+AS_IF([test x"$USE_MPI" = xyes],
+  [AC_DEFINE([USE_MPI],[1],[parallel I/O requested and available])])
 #  ----------------------------------------------------------------------
 #  Create the Fortran Interface via iso_c_binding module (Fortran 2003 Standard)
 AC_ARG_ENABLE(iso-c-interface,
@@ -181,8 +180,6 @@ ACX_CHECK_CFINT([$srcdir/src/cfortran.h])
 
 AC_SUBST([CPPFLAGS])
 
-AS_IF([test "x${replace_cc}" != "x"],[CC=$replace_cc])
-
 AC_OUTPUT(Makefile src/Makefile interfaces/Makefile app/Makefile tests/Makefile examples/Makefile cdi.settings)
 
 #  ----------------------------------------------------------------------

src/config.h.in

@@ -161,6 +161,9 @@
 /* User name */
 #undef USER_NAME
 
+/* parallel I/O requested and available */
+#undef USE_MPI
+
 /* Version number of package */
 #undef VERSION
 

src/file.c

@@ -21,7 +21,7 @@ size_t getpagesize(void);
 
 /* begin deike */
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "pio.h"
 #include "cdi.h"
 extern pioInfo *pioinfo;
@@ -1066,7 +1066,7 @@ int fileOpen(const char *filename, const char *mode)
   bfile_t *fileptr = NULL;
 
   /* begin deike */
-#ifndef NOMPI
+#ifdef USE_MPI
   if ( memcmp ( mode, "w", 1 ) == 0 && pioinfo->type != PIO_NONE )
     return pioFileOpenW ( filename );
 #endif
@@ -1161,7 +1161,7 @@ int fileClose(int fileID)
   bfile_t *fileptr;
 
   /* begin deike */
-#ifndef NOMPI
+#ifdef USE_MPI
   if ( pioinfo->type != PIO_NONE )
       return pioFileClose ( fileID );
 #endif

src/make_cdilib

@@ -50,7 +50,7 @@ cat > ${PROG} << EOR
 #include <aio.h>
 #endif
 #include <stdbool.h>
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "mpi.h"
 #endif 
 #include <assert.h>

src/pio.c

+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
-#ifndef NOMPI
+#ifdef USE_MPI
 
 #include "mpi.h"
 #include "cdi.h"
@@ -15,7 +19,7 @@
 
 bool ddebug = false;
 
-#ifndef NOMPI
+#ifdef USE_MPI
 
 char * command2charP[6] = {"IO_Open_file", "IO_Close_file",
 			   "IO_Get_fp","IO_Set_fp",
@@ -347,7 +351,7 @@ void setPioCommunicator ( MPI_Comm *myComm, MPI_Comm commF2C, int *color,
 
 int pioInit ( int ptype, int commF, int *color, int *nnodes, int *pioCollComm2F )
 {
-#ifndef NOMPI
+#ifdef USE_MPI
   MPI_Comm comm;
   int size, rank;
 #endif
@@ -356,7 +360,7 @@ int pioInit ( int ptype, int commF, int *color, int *nnodes, int *pioCollComm2F
   *color = 1;
   *pioCollComm2F = 0;
 
-#ifndef NOMPI
+#ifdef USE_MPI
   
   comm = MPI_COMM_NULL;
 
@@ -442,7 +446,7 @@ int pioInit ( int ptype, int commF, int *color, int *nnodes, int *pioCollComm2F
 
 void pioFinalize ()
 {
-#ifndef NOMPI
+#ifdef USE_MPI
   switch ( pioinfo->type )
     {
     case PIO_POSIX_FPGUARD_THREAD:

src/pio.h

 #ifndef _PIO_H
 #define _PIO_H
 
-#ifndef NOMPI
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#ifdef USE_MPI
 #include <stdlib.h>
 #include "mpi.h"
 

src/pio_dbuffer.c

 #define _XOPEN_SOURCE 600
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdbool.h>
@@ -7,7 +11,7 @@
 #include <unistd.h>
 #include <string.h>
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "pio_impl.h"
 
 bool ldebug    =true;

src/pio_impl.h

 #ifndef _PIO_IMPL_H
 #define _PIO_IMPL_H
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 #include <stdbool.h>
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "mpi.h"
 
 typedef enum 

src/pio_mpinonb.c

-#ifndef NOMPI
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#ifdef USE_MPI
 
 #include <stdbool.h>
 #include <stdio.h>

src/pio_posixasynch.c

@@ -2,8 +2,12 @@
    todo  
    README: specialRank Pe closes down, when all output files are closed    
 */
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #ifndef _SX
 
 #include <stdbool.h>

src/pio_posixfpguardsendrecv.c

@@ -4,7 +4,11 @@
    ( pioOpenFile member name, recv in tmpbuffer, if(!uniqueName(q,v,n))abort )
 */
 
-#ifndef NOMPI
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#ifdef USE_MPI
 
 #include <stdio.h>
 #include <stdbool.h>

src/pio_posixfpguardthread.c

@@ -4,8 +4,11 @@
    mutexes for each filedatas offset
    mutex for queue
 */
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
 
-#ifndef NOMPI
+#ifdef USE_MPI
 
 #include <pthread.h>
 #include <stdlib.h>

src/pio_posixfpguardthreadrefuse.c

@@ -12,7 +12,11 @@
    change condition to refuse of message ( without hard coding )
 */
 
-#ifndef NOMPI
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#ifdef USE_MPI
 
 #include <pthread.h>
 #include <stdlib.h>

src/pio_posixnonb.c

 //pio_posixnonb.c:693: warning: pointer targets in passing argument 2 of ‘strncpy’ differ in signedness
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 
-#ifndef NOMPI
+#ifdef USE_MPI
 
 #include <stdbool.h>
 #include <stdio.h>

src/pio_queue.c

+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "pio_impl.h"
 
 queue *queueInit ( valDestroyFunction vD, keyCompareFunction kC )

src/stream_grb.c

-#if defined (HAVE_CONFIG_H)
+#ifdef HAVE_CONFIG_H
 #  include "config.h"
 #endif
 
@@ -66,7 +66,7 @@ int grib2ltypeToZaxisType(int grib_ltype)
 
 /* begin deike */
 
-#ifndef NOMPI
+#ifdef USE_MPI
 #include "pio.h"               
 extern pioInfo *pioinfo;
 #endif
@@ -579,7 +579,7 @@ int grbWriteVarSliceDP(int streamID, int varID, int levelID, const double *data,
 
   /* begin deike */
 
-#ifndef NOMPI
+#ifdef USE_MPI
   if ( pioinfo->type != PIO_NONE )
     nwrite = pioFileWrite ( fileID, tsID, gribbuffer, nbytes );
   else