NAME

       MPI_Reduce_local -  Applies a reduction operator to local arguments.

SYNOPSIS

       int MPI_Reduce_local(const void *inbuf, void *inoutbuf, int count, MPI_Datatype datatype, MPI_Op op)

INPUT PARAMETERS

       inbuf  - address of the input buffer (choice)
       count  - number of elements in each buffer (integer)
       datatype
              - data type of elements in the buffers (handle)
       op     - reduction operation (handle)

OUTPUT PARAMETERS

       inoutbuf
              - address of input-output buffer (choice)

THREAD AND INTERRUPT SAFETY

       This routine is thread-safe.  This means that this routine may be safely used by multiple threads without
       the  need  for  any  user-provided thread locks.  However, the routine is not interrupt safe.  Typically,
       this is due to the use of memory allocation routines such as malloc or other non-MPICH  runtime  routines
       that are themselves not interrupt-safe.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

NOTES ON COLLECTIVE OPERATIONS

       The reduction functions ( MPI_Op ) do not return an error value.  As a result, if the functions detect an
       error,  all  they  can do is either call MPI_Abort or silently skip the problem.  Thus, if you change the
       error handler from MPI_ERRORS_ARE_FATAL to something else, for example, MPI_ERRORS_RETURN , then no error
       may be indicated.

       The reason for this is the performance problems in ensuring that all collective routines return the  same
       error value.

ERRORS

       All  MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the
       function and Fortran routines in the last argument.  Before the value is returned, the current MPI  error
       handler  is called.  By default, this error handler aborts the MPI job.  The error handler may be changed
       with   MPI_Comm_set_errhandler   (for   communicators),   MPI_File_set_errhandler   (for   files),    and
       MPI_Win_set_errhandler  (for  RMA windows).  The MPI-1 routine MPI_Errhandler_set may be used but its use
       is deprecated.  The predefined error handler MPI_ERRORS_RETURN may be used to cause error  values  to  be
       returned.   Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI
       implementations will attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is often valid.
       MPI_ERR_TYPE
              - Invalid datatype argument.  Additionally, this error can occur if  an  uncommitted  MPI_Datatype
              (see MPI_Type_commit ) is used in a communication call.
       MPI_ERR_BUFFER
              - Invalid buffer pointer.  Usually a null buffer where one is not valid.
       MPI_ERR_BUFFER
              -  This error class is associcated with an error code that indicates that two buffer arguments are
              aliased ; that is, the describe overlapping storage (often  the  exact  same  storage).   This  is
              prohibited  in  MPI  (because  it  is  prohibited  by the Fortran standard, and rather than have a
              separate case for C and Fortran, the MPI  Forum  adopted  the  more  restrictive  requirements  of
              Fortran).

                                                   11/12/2019                                MPI_Reduce_local(3)