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**NAME**

MPI_Type_lb- Returns the lower bound of a data type -- use of this routine is deprecated.

**SYNTAX**

**C** **Syntax**

#include <mpi.h> int MPI_Type_lb(MPI_Datatypedatatype, MPI_Aint*displacement)

**Fortran** **Syntax**

INCLUDE 'mpif.h' MPI_TYPE_LB(DATATYPE,DISPLACEMENT,IERROR) INTEGERDATATYPE,DISPLACEMENT,IERROR

**INPUT** **PARAMETER**

datatype Datatype (handle).

**OUTPUT** **PARAMETERS**

displacement Displacement of lower bound from origin, in bytes (integer). IERROR Fortran only: Error status (integer).

**DESCRIPTION**

Note that use of this routine isdeprecatedas of MPI-2. Please use MPI_Type_get_extent instead. This deprecated routine is not available in C++. MPI_Type_lb returns the lower bound of a data type. This may differ from zero if the type was constructed using MPI_LB. The "pseudo-datatypes," MPI_LB and MPI_UB, can be used, respectively, to mark the lower bound (or the upper 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 = {(type0, disp0), ..., (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)) + e if no entry has ub(Typemap) = ( basic type ub (max(j) {disp(j) such that type(j) = ub} otherwise Then 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).

**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. 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.

**SEE** **ALSO**

MPI_Type_get_extent