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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,
void *buf, int count, MPI_Datatype datatype, MPI_Request *request)
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
#include <mpi.h>
MPI::Request MPI::File::Iwrite_at(MPI::Offset offset, const void* buf,
int count, const MPI::Datatype& datatype)
- 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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