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

       USE MPI
       ! or the older form: 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.