MPI_File_set_info(3OpenMPI) MPI_File_set_info(3OpenMPI)
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)
INPUT/OUTPUT PARAMETER
fh File handle (handle).
INPUT PARAMETER
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 pro-vide provide
vide 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 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_set_info(3OpenMPI)
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