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MPI_File_set_info(3OpenMPI)                                                      MPI_File_set_info(3OpenMPI)



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 pro-vide provide
       vide 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 con-tiguous contiguous
       tiguous 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 col-lective collective
       lective 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.




Open MPI 1.2                                   September 2006                    MPI_File_set_info(3OpenMPI)

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