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
- 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.