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MPI_File_iwrite_at - Writes a file at an explicitly specified
offset (nonblocking, noncollective).
C Syntax
#include <mpi.h>
int MPI_File_iwrite_at(MPI_File fh, MPI_Offset offset,
const void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_FILE_IWRITE_AT(FH, OFFSET, BUF, COUNT, DATATYPE, REQUEST, IERROR)
<type> BUF(*)
INTEGER FH, COUNT, DATATYPE, REQUEST, IERROR
INTEGER(KIND=MPI_OFFSET_KIND) OFFSET
USE mpi_f08
MPI_File_iwrite_at(fh, offset, buf, count, datatype, request, ierror)
TYPE(MPI_File), INTENT(IN) :: fh
INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
INTEGER, INTENT(IN) :: count
TYPE(MPI_Datatype), INTENT(IN) :: datatype
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
- fh
- File handle (handle).
- offset
- File
offset (integer).
- buf
- Initial address of buffer (choice).
- count
- Number of
elements in buffer (integer).
- datatype
- Data type of each buffer element
(handle).
- request
- Request object (handle).
- IERROR
- Fortran
only: Error status (integer).
MPI_File_iwrite_at is a nonblocking
version of MPI_File_write_at. It attempts to write into the file associated
with fh (at the offset position) a total number of count data items having
datatype type from the user’s buffer buf. The offset is in etype units relative
to the current view. That is, holes are not counted when locating an offset.
The data is written into those parts of the file specified by the current
view. MPI_File_iwrite_at stores the number of datatype elements actually
written in status. All other fields of status are undefined. The request
structure can be passed to MPI_Wait or MPI_Test, which will return a status
with the number of bytes actually accessed.
It is erroneous to call this
function if MPI_MODE_SEQUENTIAL mode was specified when the file was open.
The MPI standard prescribes portable Fortran syntax for
the OFFSET argument only for Fortran 90. FORTRAN 77 users may use the non-portable
syntax
INTEGER*MPI_OFFSET_KIND OFFSET
where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length
of the declared integer in bytes.
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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