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)

       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.