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.. _mpi_file_set_info:
MPI_File_set_info
=================
.. include_body
:ref:`MPI_File_set_info` |mdash| Sets new values for hints (collective).
SYNTAX
------
C Syntax
^^^^^^^^
.. code-block:: c
#include <mpi.h>
int MPI_File_set_info(MPI_File fh, MPI_Info info)
Fortran Syntax
^^^^^^^^^^^^^^
.. code-block:: fortran
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_SET_INFO(FH, INFO, IERROR)
INTEGER FH, INFO, IERROR
Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^
.. code-block:: fortran
USE mpi_f08
MPI_File_set_info(fh, info, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(MPI_Info), INTENT(IN) :: info
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
INPUT/OUTPUT PARAMETER
----------------------
* ``fh``: File handle (handle).
INPUT PARAMETER
---------------
* ``info``: Info object (handle).
OUTPUT PARAMETER
----------------
* ``ierror``: Fortran only: Error status (integer).
DESCRIPTION
-----------
:ref:`MPI_File_set_info` is a collective routine that sets new values
for the hints of the file associated with *fh*. These hints are set
for each file, using the :ref:`MPI_File_open`, :ref:`MPI_File_delete`,
:ref:`MPI_File_set_view`, and :ref:`MPI_File_set_info` routines. The
opaque *info* object, which allows you to provide hints for
optimization of your code, may be different on each process, but some
*info* entries are required to be the same on all processes: In these
cases, they must appear with the same value in each process's info
object. See the :ref:`HINTS section <man-openmpi-mpi-file-set-info>`
for a list of hints that can be set.
.. _man-openmpi-mpi-file-set-info:
HINTS
-----
The following hints can be used as values for the *info* argument.
**SETTABLE HINTS**
* ``shared_file_timeout``: Amount of time (in seconds) to wait for
access to the shared file pointer before exiting with
``MPI_ERR_TIMEDOUT``.
* ``rwlock_timeout``: Amount of time (in seconds) to wait for
obtaining a read or write lock on a contiguous chunk of a UNIX file
before exiting with ``MPI_ERR_TIMEDOUT``.
* ``noncoll_read_bufsize``: Maximum size of the buffer used by MPI I/O
to satisfy read requests in the noncollective data-access
routines.
.. note:: A buffer size smaller than the distance (in bytes) in a
UNIX file between the first byte and the last byte of the
access request causes MPI I/O to iterate and perform
multiple UNIX ``read()`` or ``write()`` calls. If the request
includes multiple noncontiguous chunks of data, and the
buffer size is greater than the size of those chunks, then
the UNIX ``read()`` or ``write()`` (made at the MPI I/O level)
will access data not requested by this process in order to
reduce the total number of ``write()`` calls made. If this is
not desirable behavior, you should reduce this buffer size
to equal the size of the contiguous chunks within the
aggregate request.
* ``noncoll_write_bufsize``: Maximum size of the buffer used by MPI
I/O to satisfy write requests in the noncollective data-access
routines.
See the above note in ``noncoll_read_bufsize``.
* ``coll_read_bufsize``: Maximum size of the buffer used by MPI I/O to
satisfy read requests in the collective data-access routines.
See the above note in ``noncoll_read_bufsize``.
* ``coll_write_bufsize``: Maximum size of the buffer used by MPI I/O
to satisfy write requests in the collective data-access
routines.
See the above note in ``noncoll_read_bufsize``.
* ``mpiio_concurrency``: (boolean) controls whether nonblocking I/O
routines can bind an extra thread to an LWP.
* ``mpiio_coll_contiguous``: (boolean) controls whether subsequent
collective data accesses will request collectively contiguous
regions of the file.
**NON-SETTABLE HINTS**
* ``filename``: Access this hint to get the name of the file.
ERRORS
------
.. include:: ./ERRORS.rst
|
