MPI_File_set_view
Changes process's view of data in file (collective).
#include <mpi.h>
int MPI_File_set_view(MPI_File fh, MPI_Offset disp,
MPI_Datatype etype, MPI_Datatype filetype,
const char *datarep, MPI_Info info)
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_SET_VIEW(FH, DISP, ETYPE,
FILETYPE, DATAREP, INFO, IERROR)
INTEGER FH, ETYPE, FILETYPE, INFO, IERROR
CHARACTER*(*) DATAREP
INTEGER(KIND=MPI_OFFSET_KIND) DISP
USE mpi_f08
MPI_File_set_view(fh, disp, etype, filetype, datarep, info, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: disp
TYPE(MPI_Datatype), INTENT(IN) :: etype, filetype
CHARACTER(LEN=*), INTENT(IN) :: datarep
TYPE(MPI_Info), INTENT(IN) :: info
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
fh
: File handle (handle).
disp
: Displacement (integer).etype
: Elementary data type (handle).filetype
: File type (handle). See Restrictions, below.datarep
: Data representation (string).info
: Info object (handle).
ierror
: Fortran only: Error status (integer).
The MPI_File_set_view
routine changes the process's view of the data in the file the beginning of the data accessible in the file through that view is set to disp; the type of data is set to etype; and the distribution of data to processes is set to filetype. In addition, MPI_File_set_view
resets the independent file pointers and the shared file pointer to zero. MPI_File_set_view
is collective across the fh; all processes in the group must pass identical values for datarep and provide an etype with an identical extent. The values for disp, filetype, and info may vary. It is erroneous to use the shared file pointer data-access routines unless identical values for disp and filetype are also given. The data types passed in etype and filetype must be committed.
The disp displacement argument specifies the position (absolute offset in bytes from the beginning of the file) where the view begins.
The MPI_File_set_view
interface allows the user to pass a data-representation string to MPI I/O via the datarep argument. To obtain the default value pass the value "native". The user can also pass information via the info argument. See the HINTS section
<man-openmpi-mpi-file-set-view>
for a list of hints that can be set.
The following hints can be used as values for the info argument.
SETTABLE HINTS
MPI_INFO_NULL
shared_file_timeout
: Amount of time (in seconds) to wait for access to the shared file pointer before exiting withMPI_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 withMPI_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.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()
orwrite()
calls. If the request includes multiple noncontiguous chunks of data, and the buffer size is greater than the size of those chunks, then the UNIXread()
orwrite()
(made at the MPI I/O level) will access data not requested by this process in order to reduce the total number ofwrite()
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.noncoll_write_bufsize
: Maximum size of the buffer used by MPI I/O to satisfy write requests in the noncollective data-access routines.See the above note in
noncoll_read_bufsize
.coll_read_bufsize
: Maximum size of the buffer used by MPI I/O to satisfy read requests in the collective data-access routines.See the above note in
noncoll_read_bufsize
.coll_write_bufsize
: Maximum size of the buffer used by MPI I/O to satisfy write requests in the collective data-access routines.See the above note in
noncoll_read_bufsize
.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.