noble (3) MPI_File_iread_at.openmpi.3.gz

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)

       USE MPI
       ! or the older form: 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

Fortran 2008 Syntax

       USE mpi_f08
       MPI_File_iread_at(fh, offset, buf, count, datatype, request, ierror)
            TYPE(MPI_File), INTENT(IN) :: fh
            INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
            TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
            INTEGER, INTENT(IN) :: count
            TYPE(MPI_Datatype), INTENT(IN) :: datatype
            TYPE(MPI_Request), INTENT(OUT) :: request
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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.