MPI_File_get_info(3OpenMPI) MPI_File_get_info(3OpenMPI)
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 asso-ciates associates
ciates 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 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_get_info(3OpenMPI)
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