MPI_Type_get_true_extent(3)

NAME
MPI_Type_get_true_extent, MPI_Type_get_true_extent_x - Returns the true lower bound and extent of a data type's corresponding typemap, ignoring MPI_UB and MPI_LB markers.

SYNTAX

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

Fortran Syntax (see FORTRAN 77 NOTES)
USE MPI
! or the older form: 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
MPI_TYPE_GET_TRUE_EXTENT_X(DATATYPE, TRUE_LB, TRUE_EXTENT, IERROR)
	INTEGER	DATATYPE, IERROR
	INTEGER(KIND=MPI_COUNT_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. For both functions, if either the true_lb or true_extent parameter cannot express the value to be returned (e.g., if the parameter is too small to hold the output value), it is set to MPI_UNDEFINED.

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

See § 4.1.8 of the MPI-3 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

MPI_Type_get_true_extent:

     INTEGER*MPI_ADDRESS_KIND TRUE_LB
or
     INTEGER*MPI_ADDRESS_KIND TRUE_EXTENT

MPI_Type_get_true_extent_x:

     INTEGER*MPI_COUNT_KIND TRUE_LB
or
     INTEGER*MPI_COUNT_KIND TRUE_EXTENT

where MPI_ADDRESS_KIND and MPI_COUNT_KIND are constants defined in mpif.h and give 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.