MPI_Type_get_true_extent.openmpi: Returns the true lower bound and extent of a data type's corresponding typemap, ignoring mpi_ub and mpi

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Type_get_true_extent(MPI_Datatype datatype,
	MPI_Aint *true_lb, MPI_Aint *true_extent)

Fortran Syntax (see FORTRAN 77 NOTES)

INCLUDE 'mpif.h'
MPI_TYPE_GET_TRUE_EXTENT(DATATYPE, TRUE_LB, TRUE_EXTENT, IERROR)
	INTEGER	DATATYPE, IERROR
	INTEGER(KIND=MPI_ADDRESS_KIND) TRUE_LB, TRUE_EXTENT

C++ Syntax

#include <mpi.h>
void MPI::Datatype::Get_true_extent(MPI::Aint& true_lb,
	MPI::Aint& true_extent) const

INPUT PARAMETER

datatype: Data type for which information is wanted (handle).

OUTPUT PARAMETERS

true_lb: True lower bound of data type (integer).
true_extent: True size of data type (integer).
IERROR: Fortran only: Error status (integer).

DESCRIPTION

The true_lb parameter returns the offset of the lowest unit of store that is addressed by the data type, that is, the lower bound of the corresponding typemap, ignoring MPI_LB markers. The true_extent parameter returns the true size of the data type, that is, the extent of the corresponding typemap, ignoring MPI_LB and MPI_UB markers, and performing no rounding for alignment.

The true_extent is the minimum number of bytes of memory necessary to hold a data type, uncompressed.

See Section 4.14.3 of the MPI-2 standard for more detailed definitions of these parameters in relation to the typemap.

FORTRAN 77 NOTES

The MPI standard prescribes portable Fortran syntax for the TRUE_LB and TRUE_EXTENT arguments only for Fortran 90. FORTRAN 77 users may use the non-portable syntax

     INTEGER*MPI_ADDRESS_KIND TRUE_LB
or
     INTEGER*MPI_ADDRESS_KIND TRUE_EXTENT

where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.

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.

MPI_Type_get_true_extent.openmpi (3)