17.2.403. MPI_Type_get_true_extent

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.

17.2.403.1. SYNTAX

17.2.403.1.1. 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)

17.2.403.1.2. 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

17.2.403.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Type_get_true_extent(datatype, true_lb, true_extent, ierror)
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: true_lb, true_extent
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Type_get_true_extent_x(datatype, true_lb, true_extent, ierror)
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     INTEGER(KIND = MPI_COUNT_KIND), INTENT(OUT) :: true_lb, true_extent
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.403.2. INPUT PARAMETER

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

17.2.403.3. 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).

17.2.403.4. 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 section 4.1.8 of the MPI-3 standard for more detailed definitions of these parameters in relation to the typemap.

17.2.403.5. 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.

17.2.403.6. 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.