NAME

       MPI_File_iwrite_at - Writes a file at an explicitly specified offset (nonblocking, noncollective).

SYNTAX

       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)

Fortran Syntax (see FORTRAN 77 NOTES)

           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

C++ Syntax

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

INPUT/OUTPUT PARAMETER

       fh        File handle (handle).

INPUT PARAMETERS

       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).

OUTPUT PARAMETERS

       request   Request object (handle).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       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.

FORTRAN 77 NOTES

       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.

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.