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

       Almost all MPI routines return an error value; C routines as  the  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                       MPI_TYPE_GET_TRUE_EXTENT(3)