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MPI_Type_get_true_extent.3.rst

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MPI_Type_get_true_extent

:ref:`MPI_Type_get_true_extent`, :ref:`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

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

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

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

ERRORS