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MPI_Type_lb(3) man page (version 5.0.0rc2)

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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_Datatype datatype, MPI_Aint *displacement)

Fortran Syntax


INCLUDE ’mpif.h’
MPI_TYPE_LB(DATATYPE, DISPLACEMENT, IERROR)
    INTEGER    DATATYPE, 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 is deprecated as of MPI-2. Please use MPI_Type_get_extent instead.

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.

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


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