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MPI_File_read_ordered_begin(3OpenMPI)                                  MPI_File_read_ordered_begin(3OpenMPI)



NAME
       MPI_File_read_ordered_begin  -  Reads a file at a location specified by a shared file pointer; begin-ning beginning
       ning 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
           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.




Open MPI 1.2                                   September 2006          MPI_File_read_ordered_begin(3OpenMPI)