18.2.404. 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.

18.2.404.1. SYNTAX

18.2.404.1.1. 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)

18.2.404.1.2. 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

18.2.404.1.3. 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

18.2.404.2. INPUT PARAMETER

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

18.2.404.3. 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).

18.2.404.4. 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.

18.2.404.5. 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.

18.2.404.6. 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[_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.

In the sessions model, the error handler can be set during MPI_Session_init.

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.

Custom MPI error handlers can be created by calling: MPI_Comm_create_errhandler(3) MPI_File_create_errhandler(3) MPI_Session_create_errhandler(3) MPI_Win_create_errhandler(3)

Predefined and custom error handlers can be set by calling: MPI_Comm_set_errhandler(3) MPI_File_set_errhandler(3) MPI_Session_set_errhandler(3) MPI_Win_set_errhandler(3)

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 standard for more information.