MPI_File_get_info(3)               Open MPI               MPI_File_get_info(3)



NAME
       MPI_File_get_info - Returns a new info object containing values for
       current hints associated with a file.



SYNTAX
       C Syntax
           #include <mpi.h>
           int MPI_File_get_info(MPI_File fh, MPI_Info *info_used)

       Fortran Syntax
           INCLUDE 'mpif.h'
           MPI_FILE_GET_INFO(FH, INFO_USED, IERROR)
                  INTEGER    FH, INFO_USED, IERROR


C++ Syntax
       #include <mpi.h>
       MPI::Info MPI::File::Get_info() const


INPUT PARAMETER
       fh        File handle (handle).


OUTPUT PARAMETERS
       info_used New info object (handle).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_File_get_info returns a new info object containing all the hints
       that the system currently associates with the file fh. The current
       setting of all hints actually used by the system related to this open
       file is returned in info_used. The user is responsible for freeing
       info_used via MPI_Info_free.

       Note that the set of hints returned in info_used may be greater or
       smaller than the set of hints passed in to MPI_File_open,
       MPI_File_set_view, and MPI_File_set_info, as the system may not
       recognize some hints set by the user, and may automatically set other
       hints that the user has not requested to be set. 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_used 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_get_info(3)
