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.