MPI_File_iread_at(3)               Open MPI               MPI_File_iread_at(3)



NAME
       MPI_File_iread_at - Reads a file at an explicitly specified offset
       (nonblocking, noncollective).


SYNTAX
       C Syntax
           #include <mpi.h>
           int MPI_File_iread_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_IREAD_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::Iread_at(MPI::Offset offset, void* buf,
            int count, const MPI::Datatype& datatype)


INPUT PARAMETERS
       fh        File handle (handle).

       offset    File offset (integer).

       count     Number of elements in the buffer (integer).

       datatype  Data type of each buffer element (handle).


OUTPUT PARAMETERS
       buf       Initial address of the buffer (choice).

       request   Request object (handle).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_File_iread_at is the nonblocking version of MPI_File_read_at.

       MPI_File_iread_at is a nonblocking routine that attempts to read from
       the file associated with fh at the offset position a total number of
       count data items having datatype type into 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 taken out of those
       parts of the file specified by the current view. MPI_File_iread_at
       stores the number of datatype elements actually read in status.  All
       other fields of status are undefined.


FORTRAN 77 NOTES
       The MPI standard prescribes portable Fortran syntax for the OFFSET
       argument only for Fortran 90.  Sun 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.




1.4.1                            Jan 14, 2010             MPI_File_iread_at(3)
