MPI_TYPE_GET_TRUE_EXTENT(3)			     Open MPI			       MPI_TYPE_GET_TRUE_EXTENT(3)

MPI_Type_get_true_extent,  MPI_Type_get_true_extent_x <#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
       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>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#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	<#
       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>/MPI_Comm_spawn_multiple	<#
       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 <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#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	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

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

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

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

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026			       MPI_TYPE_GET_TRUE_EXTENT(3)
