.. _mpi_type_get_contents:


MPI_Type_get_contents
=====================

.. include_body

:ref:`MPI_Type_get_contents` - Returns information about arguments used in
creation of a data type.


SYNTAX
------


C Syntax
^^^^^^^^

.. code-block:: c

   #include <mpi.h>

   int MPI_Type_get_contents(MPI_Datatype datatype, int max_integers,
   	int max_addresses, int max_datatypes, int array_of_integers[], MPI_Aint array_of_addresses[], MPI_Datatype array_of_datatypes[])


Fortran Syntax (see FORTRAN 77 NOTES)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: fortran

   USE MPI
   ! or the older form: INCLUDE 'mpif.h'
   MPI_TYPE_GET_CONTENTS(DATATYPE, MAX_INTEGERS, MAX_ADDRESSES,
   		MAX_DATATYPES, ARRAY_OF_INTEGERS, ARRAY_OF_ADDRESSES,
   		ARRAY_OF_DATATYPES, IERROR)
   	INTEGER	DATATYPE, MAX_INTEGERS, MAX_ADDRESSES, MAX_DATATYPES
   	INTEGER	ARRAY_OF_INTEGERS(*), ARRAY_OF_DATATYPES(*), IERROR
   	INTEGER(KIND=MPI_ADDRESS_KIND) ARRAY_OF_ADDRESSES(*)


Fortran 2008 Syntax
^^^^^^^^^^^^^^^^^^^

.. code-block:: fortran

   USE mpi_f08
   MPI_Type_get_contents(datatype, max_integers, max_addresses, max_datatypes,
   	array_of_integers, array_of_addresses, array_of_datatypes,
   		ierror)
   	TYPE(MPI_Datatype), INTENT(IN) :: datatype
   	INTEGER, INTENT(IN) :: max_integers, max_addresses, max_datatypes
   	INTEGER, INTENT(OUT) :: array_of_integers(max_integers)
   	INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) ::
   	array_of_addresses(max_addresses)
   	TYPE(MPI_Datatype), INTENT(OUT) :: array_of_datatypes(max_datatypes)
   	INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT PARAMETERS
----------------
* ``datatype``: Data type to access (handle).
* ``max_integers``: Number of elements in *array_of_integers (nonnegative integer).*
* ``max_addresses``: Number of elements in *array_of_addresses (nonnegative integer).*
* ``max_datatypes``: Number of elements in *array_of_datatypes (nonnegative integer).*

OUTPUT PARAMETERS
-----------------
* ``array_of_integers``: Contains integer arguments used in constructing *datatype (array of integers).*
* ``array_of_addresses``: Contains address arguments used in constructing *datatype (array of integers).*
* ``array_of_datatypes``: Contains data-type arguments used in constructing *datatype (array of integers).*
* ``IERROR``: Fortran only: Error status (integer).

DESCRIPTION
-----------

For the given data type, :ref:`MPI_Type_get_envelope` returns information on
the number and type of input arguments used in the call that created the
data type. The number-of-arguments values returned can be used to
provide sufficiently large arrays in the decoding routine
:ref:`MPI_Type_get_contents`. This call and the meaning of the returned values
is described below. The combiner reflects the MPI data type constructor
call that was used in creating *datatype.*

The parameter *datatype must be a predefined unnamed or a derived data
type. The call is erroneous if datatype is a predefined named data
type.*

The values given for *max_integers, max_addresses, and max_datatypes
must be at least as large as the value returned in num_integers,
num_addresses, and num_datatypes, respectively, in the call
:ref:`MPI_Type_get_envelope` for the same datatype argument.*

The data types returned in *array_of_datatypes are handles to data-type
objects that are equivalent to the data types used in the original
construction call. If these were derived data types, then the returned
data types are new data-type objects, and the user is responsible for
freeing these datatypes with :ref:`MPI_Type_free`. If these were predefined
data types, then the returned data type is equal to that (constant)
predefined data type and cannot be freed.*

The committed state of returned derived data types is undefined, that
is, the data types may or may not be committed. Furthermore, the content
of attributes of returned data types is undefined.

Note that :ref:`MPI_Type_get_contents` can be invoked with a data-type argument
that was constructed using :ref:`MPI_Type_create_f90_real`,
:ref:`MPI_Type_create_f90_integer`, or :ref:`MPI_Type_create_f90_complex` (an unnamed
predefined data type). In such a case, an empty *array_of_datatypes is
returned.*

In the MPI-1 data-type constructor calls, the address arguments in
Fortran are of type INTEGER. In the new MPI-2 calls, the address
arguments are of type INTEGER(KIND=MPI_ADDRESS_KIND). The call
:ref:`MPI_Type_get_contents` returns all addresses in an argument of type
INTEGER(KIND=MPI_ADDRESS_KIND). This is true even if the old MPI-1 calls
were used. Thus, the location of values returned can be thought of as
being returned by the C bindings. It can also be determined by examining
the new MPI-2 calls for data-type constructors for the deprecated MPI-1
calls that involve addresses.


FORTRAN 77 NOTES
----------------

The MPI standard prescribes portable Fortran syntax for the
*ARRAY_OF_ADDRESSES argument only for Fortran 90. FORTRAN 77* users may
use the non-portable syntax

::

        INTEGER*MPI_ADDRESS_KIND ARRAY_OF_ADDRESSES(*)

where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives 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.

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
:ref:`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.


.. seealso::
   :ref:`MPI_Type_get_envelope`
