.. _mpi_type_get_envelope:


MPI_Type_get_envelope
=====================

.. include_body

:ref:`MPI_Type_get_envelope` - Returns information about input arguments
associated with a data type.


SYNTAX
------


C Syntax
^^^^^^^^

.. code-block:: c

   #include <mpi.h>

   int MPI_Type_get_envelope(MPI_Datatype datatype, int *num_integers,
   	int *num_addresses, int *num_datatypes, int *combiner)


Fortran Syntax
^^^^^^^^^^^^^^

.. code-block:: fortran

   USE MPI
   ! or the older form: INCLUDE 'mpif.h'
   MPI_TYPE_GET_ENVELOPE(DATATYPE, NUM_INTEGERS, NUM_ADDRESSES,
   		NUM_DATATYPES, COMBINER, IERROR)
   	INTEGER	DATATYPE, NUM_INTEGERS, NUM_ADDRESSES
   	INTEGER	NUM_DATATYPES, COMBINER, IERROR


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

.. code-block:: fortran

   USE mpi_f08
   MPI_Type_get_envelope(datatype, num_integers, num_addresses, num_datatypes,
   		combiner, ierror)
   	TYPE(MPI_Datatype), INTENT(IN) :: datatype
   	INTEGER, INTENT(OUT) :: num_integers, num_addresses, num_datatypes,
   	combiner
   	INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT PARAMETER
---------------
* ``datatype``: Data type to access (handle).

OUTPUT PARAMETERS
-----------------
* ``num_integers``: Number of input integers used in the call constructing *combiner* (nonnegative integer).
* ``num_addresses``: Number of input addresses used in the call constructing *combiner* (nonnegative integer).
* ``num_datatypes``: Number of input data types used in the call constructing *combiner* (nonnegative integer).
* ``combiner``: Combiner (state).
* ``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*.


NOTES
-----

These are the values that can be returned in *combiner* and their
associated calls:

::

   Values                          Associated Calls

   MPI_COMBINER_NAMED              a named predefined data type
   MPI_COMBINER_DUP                MPI_Type_dup
   MPI_COMBINER_CONTIGUOUS         MPI_Type_contiguous
   MPI_COMBINER_VECTOR             MPI_Type_vector
   MPI_COMBINER_HVECTOR            MPI_Type_hvector
                                     and MPI_Type_create_hvector
   MPI_COMBINER_INDEXED            MPI_Type_indexed
   MPI_COMBINER_HINDEXED           MPI_Type_hindexed
                                     and MPI_Type_create_hindexed
   MPI_COMBINER_INDEXED_BLOCK      MPI_Type_create_indexed_block
   MPI_COMBINER_STRUCT             MPI_Type_struct
                                     and MPI_Type_create_struct
   MPI_COMBINER_SUBARRAY           MPI_Type_create_subarray
   MPI_COMBINER_DARRAY             MPI_Type_create_darray
   MPI_COMBINER_F90_REAL           MPI_Type_create_f90_real
   MPI_COMBINER_F90_COMPLEX        MPI_Type_create_f90_complex
   MPI_COMBINER_F90_INTEGER        MPI_Type_create_f90_integer
   MPI_COMBINER_RESIZED            MPI_Type_create_resized

If *combiner* is MPI_COMBINER_NAMED, then *datatype* is a named
predefined data type.

The actual arguments used in the creation call for a data type can be
obtained from the call :ref:`MPI_Type_get_contents`.


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_contents`
