MPI_File_set_info(3)               Open MPI               MPI_File_set_info(3)



NAME
       MPI_File_set_info - Sets new values for hints (collective).


SYNTAX
       C Syntax
           #include <mpi.h>
           int MPI_File_set_info(MPI_File fh, MPI_Info info)

       Fortran Syntax
           INCLUDE 'mpif.h'
           MPI_FILE_SET_INFO(FH, INFO, IERROR)
                  INTEGER    FH, INFO, IERROR


C++ Syntax
       #include <mpi.h>
       void MPI::File::Set_info(const MPI::Info& info)


INPUT/OUTPUT PARAMETER
       fh        File handle (handle).


INPUT PARAMETER
       info      Info object (handle).


OUTPUT PARAMETER
       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       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 MPI_File_open, MPI_File_delete, MPI_File_set_view, and
       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 HINTS section for a list of hints that
       can be set.


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. (See
       NOTE, below.)

       - noncoll_write_bufsize: Maximum size of the buffer used by MPI I/O to
       satisfy write requests in the noncollective data-access routines. (See
       NOTE, below.)

       - coll_read_bufsize:  Maximum size of the buffer used by MPI I/O to
       satisfy read requests in the collective data-access routines. (See
       NOTE, below.)

       - coll_write_bufsize:  Maximum size of the buffer used by MPI I/O to
       satisfy write requests in the collective data-access routines. (See
       NOTE, below.)

       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.

       - 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
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is
       called. For MPI I/O function errors, the default error handler is set
       to MPI_ERRORS_RETURN. The error handler may be changed with
       MPI_File_set_errhandler; the predefined error handler
       MPI_ERRORS_ARE_FATAL may be used to make I/O errors fatal. Note that
       MPI does not guarantee that an MPI program can continue past an error.




1.4.1                            Jan 14, 2010             MPI_File_set_info(3)
