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MPI_File_get_info - Returns a new info object containing values
for current hints associated with a file.
C Syntax
#include <mpi.h>
int MPI_File_get_info(MPI_File fh, MPI_Info *info_used)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_FILE_GET_INFO(FH, INFO_USED, IERROR)
INTEGER FH, INFO_USED, IERROR
USE mpi_f08
MPI_File_get_info(fh, info_used, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
TYPE(MPI_Info), INTENT(OUT) :: info_used
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- fh
- File handle (handle).
- info_used
- New
info object (handle).
- IERROR
- Fortran only: Error status (integer).
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.
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.
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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