[svn-r5680] Purpose:

    New feature.

Description:
    There is some discussion among the SAF team as to whether it is better
    to use MPI derived types for raw data transfers (thus needing a
    MPI_File_set_view() call), or whether it is better to use a sequence of
    low-level MPI types (i.e. MPI_BYTE) for the raw data transfer.

Solution:
    Added an in internal flag to determine whether derived types are preferred
    (the default), or whether they should be avoided.  An environment variable
    ("HDF5_MPI_PREFER_DERIVED_TYPES") can be set by users to control whether MPI
    types should be used or not.  Set the environment variable to "0" (i.e.:
    'setenv HDF5_MPI_PREFER_DERIVED_TYPES 0' to avoid using MPI derived types.

Platforms tested:
    IRIX64 6.5 (modi4) w/parallel

1 files changed, 4 insertions, 2 deletions

diff --git a/src/H5Sprivate.h b/src/H5Sprivate.h
index c35cf5c..de7f838 100644
--- a/src/H5Sprivate.h
+++ b/src/H5Sprivate.h
@@ -249,8 +249,10 @@ __DLL__ htri_t H5S_mpio_opt_possible(const H5S_t *mem_space,
                                      const H5S_t *file_space, const unsigned flags);
 
 #ifndef _H5S_IN_H5S_C
-/* Global var whose value comes from environment variable */
-__DLLVAR__ hbool_t		H5_mpi_opt_types_g;
+/* Global vars whose value comes from environment variable */
+/* (Defined in H5S.c) */
+__DLLVAR__ hbool_t		H5S_mpi_opt_types_g;
+__DLLVAR__ hbool_t		H5S_mpi_prefer_derived_types_g;
 #endif /* _H5S_IN_H5S_C */
 
 #endif /* H5_HAVE_PARALLEL */