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

       USE MPI
       ! or the older form: 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.