C Syntax

#include <mpi.h>
int MPI_Type_ub(MPI_Datatype datatype, MPI_Aint *displacement)

Fortran Syntax

INCLUDE 'mpif.h'



Datatype (handle).



Displacement of upper bound from origin, in bytes (integer).


Fortran only: Error status (integer).


Note that use of this routine is deprecated as of MPI-2. Please use MPI_Type_get_extent instead.

This deprecated routine is not available in C++.

MPI_Type_ub returns the upper bound of a data type. This will differ from zero if the type was constructed using MPI_UB. The upper bound will take into account any alignment considerations.

The "pseudo-datatypes," MPI_LB and MPI_UB, can be used, respectively, to mark the upper bound (or the lower bound) of a datatype. These pseudo-datatypes occupy no space (extent (MPI_LB) = extent (MPI_UB) =0. They do not affect the size or count of a datatype, and do not affect the context of a message created with this datatype. However, they do affect the definition of the extent of a datatype and, therefore, affect the outcome of a replication of this datatype by a datatype constructor.

In general, if

    Typemap = {(type(0), disp(0)), ..., (type(n-1), disp(n-1))}

then the lower bound of Typemap is defined to be

                  (min(j) disp(j)                          if no entry has
    lb(Typemap) = (                                        basic type lb
                  (min(j) {disp(j) such that type(j) = lb} otherwise

Similarly, the upper bound of Typemap is defined to be

                  (max(j) disp(j) + sizeof(type(j) = lb}   if no entry has
    ub(Typemap) = (                                        basic type ub
                  (max(j) {disp(j) such that type(j) = ub} otherwise


    extent(Typemap) = ub(Typemap) - lb(Typemap)

If type(i) requires alignment to a byte address that is a multiple of k(i), then e is the least nonnegative increment needed to round extent(Typemap) to the next multiple of max(i) k(i).


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. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

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