Add option to disable parallel HDF use if library supports it

Former-commit-id: 0cffbe34cf5f2c782442aebdeb4a007944ca851b

configure.ac

@@ -212,20 +212,33 @@ AC_CHECK_LIB([z],[gzopen],[
     ],[])
 
 
-# Check for HDF5. Need to differentiate between parallel and serial.
+# Check for HDF5.
 AX_LIB_HDF5
 
-# Need to ask the HDF5 compiler about its configuration, -showconfig should
-# have yes/no
+# We want to know if this HDF5 supports MPI and whether we should use it.
+# The default is to use MPI support if it is available, i.e. this is
+# a parallel HDF5.
+# To do this need to ask the HDF5 compiler about its configuration,
+# -showconfig should have yes/no. 
 have_parallel_hdf5="no"
 if test "$with_hdf5" = "yes"; then
-    AC_MSG_CHECKING([for HDF5 parallel support])
-    parallel=`$H5CC -showconfig | grep "Parallel HDF5:" | awk '{print $3}'`
-    if test "$parallel" = "yes"; then
-        have_parallel_hdf5="yes"
-        AC_DEFINE([HAVE_PARALLEL_HDF5],1,[HDF5 library supports parallel access])
+    AC_ARG_ENABLE([parallel-hdf5],
+       [AS_HELP_STRING([--enable-parallel-hdf5],
+         [Enable parallel HDF5 library MPI functions if available. @<:@default=yes@:>@]
+       )],
+       [enable_parallel_hdf5="$enableval"],
+       [enable_parallel_hdf5="yes"]
+    )
+
+    if test "$enable_parallel_hdf5" = "yes"; then
+        AC_MSG_CHECKING([for HDF5 parallel support])
+        parallel=`$H5CC -showconfig | grep "Parallel HDF5:" | awk '{print $3}'`
+        if test "$parallel" = "yes"; then
+            have_parallel_hdf5="yes"
+            AC_DEFINE([HAVE_PARALLEL_HDF5],1,[HDF5 library supports parallel access])
+        fi
+        AC_MSG_RESULT($parallel)
     fi
-    AC_MSG_RESULT($parallel)
 fi
 AM_CONDITIONAL([HAVEPARALLELHDF5],[test "$have_parallel_hdf5" = "yes"])