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MPI_File_set_info - Sets new values for hints (collective).
C Syntax
#include <mpi.h>
int MPI_File_set_info(MPI_File fh, MPI_Info info)
INCLUDE ’mpif.h’
MPI_FILE_SET_INFO(FH, INFO, IERROR)
INTEGER FH, INFO, IERROR
#include <mpi.h>
void MPI::File::Set_info(const MPI::Info& info)
- fh
- File handle (handle).
- info
- Info object (handle).
- IERROR
- Fortran only: Error status
(integer).
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.
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.
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.
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