noble (3) MPI_File_set_view.openmpi.3.gz
NAME
MPI_File_set_view - Changes process's view of data in file (collective).
SYNTAX
C Syntax
#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)
Fortran Syntax (see FORTRAN 77 NOTES)
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
Fortran 2008 Syntax
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
C++ Syntax
#include <mpi.h>
void MPI::File::Set_view(MPI::Offset disp,
const MPI::Datatype& etype,
const MPI::Datatype& filetype, const char* datarep,
const MPI::Info& info)
INPUT/OUTPUT PARAMETER
fh File handle (handle).
INPUT PARAMETERS
disp Displacement (integer).
etype Elementary data type (handle).
filetype File type (handle). See Restrictions, below.
datarep Data representation (string).
info Info object (handle).
OUTPUT PARAMETER
IERROR Fortran only: Error status (integer).
DESCRIPTION
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 (or "native"), pass NULL. The user can also pass
information via the info argument. See the HINTS section for a list of hints that can be set. For more
information, see the MPI-2 standard.
HINTS
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 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.
FORTRAN 77 NOTES
The MPI standard prescribes portable Fortran syntax for the DISP argument only for Fortran 90. FORTRAN
77 users may use the non-portable syntax
INTEGER*MPI_OFFSET_KIND DISP
where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in
bytes.
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.