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)
- fh
- File handle (handle).
- 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 provide 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 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.