NAME

       MPI_File_read_ordered  -  Reads  a  file  at a location specified by a shared file pointer
       (blocking, collective).

SYNTAX

C Syntax

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

Fortran Syntax

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

C++ Syntax

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

       void MPI::File::Read_ordered(void* buf, int count,
            const MPI::Datatype& datatype)

INPUT PARAMETERS

       fh        File handle (handle).

       count     Number of elements in buffer (integer).

       datatype  Data type of each buffer element (handle).

OUTPUT PARAMETERS

       buf       Initial address of buffer (choice).

       status    Status object (Status).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_File_read_ordered is a  collective  routine.  This  routine  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. MPI_File_read_ordered returns the actual number of datatype elements read in status.
       The shared file pointer is updated by the amounts of data requested by  all  processes  of
       the group.

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.