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MPI_Type_lb - Returns the lower bound of a data type. This may differ
from zero if the type was constructed using MPI_LB. Use of this routine
is deprecated.
#include <mpi.h>
int MPI_Type_lb(MPI_Datatype datatype, MPI_Aint *displacement)
INCLUDE ’mpif.h’
MPI_TYPE_LB(DATATYPE, DISPLACEMENT, IERROR)
INTEGER DATATYPE, DISPLACEMENT, IERROR
- datatype
- Datatype (handle).
- displacement
- Displacement of lower bound from origin, in bytes (integer).
- IERROR
- 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_lb returns the
lower bound of a data type.
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).
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.
MPI_Type_get_extent
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