NAME

       MPI_File_read_ordered_begin  -  Reads  a  file  at  a  location specified by a shared file
       pointer; beginning part of a split collective routine (nonblocking).

SYNTAX

C Syntax

       #include <mpi.h> int MPI_File_read_ordered_begin(MPI_File fh, void *buf,       int  count,
       MPI_Datatype datatype)

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_FILE_READ_ORDERED_BEGIN(FH, BUF, COUNT, DATATYPE, IERROR)
            <type>    BUF(*)
            INTEGER   FH, COUNT, DATATYPE, IERROR

C++ Syntax

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

INPUT/OUTPUT PARAMETER

       fh        File handle (handle).

INPUT PARAMETERS

       count     Number of elements in buffer (integer).

       datatype  Data type of each buffer element (handle).

OUTPUT PARAMETERS

       buf       Initial address of buffer (choice).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_File_read_ordered_begin  is  the  beginning  part  of  a split collective, nonblocking
       routine that must be called by all processes in the communicator group associated with the
       file  handle  fh.   Each  process  may pass different argument values for the datatype and
       count arguments. Each process attempts to read, from the file associated with fh, a  total
       number  of  count  data  items  having datatype type into the user's buffer buf.  For each
       process, the location in the file at which data is read  is  the  position  at  which  the
       shared  file  pointer  would  be after all processes whose ranks within the group are less
       than that of this process had read their data.

NOTES

       All the nonblocking collective routines for data access are  "split"  into  two  routines,
       each  with  _begin or _end as a suffix. These split collective routines are subject to the
       semantic rules described in Section 9.4.5 of the MPI-2 standard.

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.