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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 set-
ting 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 recog-
nize 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.
- 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 rou-
tines can bind an extra thread to an LWP.
- mpiio_coll_contiguous: (boolean) controls whether subsequent collec-
tive 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++ func-
tions 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_get_info(3OpenMPI)
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