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MPI_File_iwrite_at(3OpenMPI)                                                    MPI_File_iwrite_at(3OpenMPI)



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,
                  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 spec-ified specified
       ified 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_SEQENTIAL 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.




Open MPI 1.2                                   September 2006                   MPI_File_iwrite_at(3OpenMPI)