.. _extpredictor:

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External Loadstep Predictor
###########################

.. \index{TYPE!in Loadstep Predictor!description of}

.. warning::

   The external loadstep predictor is for implicit analyses only.

Production-ready loadstep predictor types are available in the Sierra/SM User Guide. The ``LOADSTEP PREDICTOR`` command block controls the behavior of the predictor that is used to predict the solution at the beginning of a new load step. This command block is placed in the ``SOLVER`` scope.

The ``EXTERNAL``, ``EXTERNAL_FIRST`` and ``TANGENT`` predictor types are special use capabilities currently under development.

.. code-block:: sierrainput

   BEGIN LOADSTEP PREDICTOR
     TYPE = <string>EXTERNAL|EXTERNAL_FIRST|TANGENT
   END [LOADSTEP PREDICTOR]

The tangent predictor is selected with the ``TANGENT`` option, which is useful in combination with the tangent preconditioner. This type of predictor uses the tangent preconditioner to estimate the next load step's solution.

at new load steps.  For instance, the external predictor file can come from the results output of a previous model run that included the command ``OUTPUT EXTERNAL PREDICTOR VARIABLES`` in the output block, i.e.:

.. code-block:: sierrainput

   BEGIN RESULTS OUTPUT
     OUTPUT EXTERNAL PREDICTOR VARIABLES
   END [RESULTS OUTPUT]

If you would like to try the external predictor, please contact Sierra support for more information.
at new load steps.  For instance, the external predictor file can come from the results output of a previous model run that included the command ``OUTPUT EXTERNAL PREDICTOR VARIABLES`` in the output block, i.e.:

.. code-block:: sierrainput

   BEGIN RESULTS OUTPUT
     OUTPUT EXTERNAL PREDICTOR VARIABLES
   END [RESULTS OUTPUT]

If you would like to try the external predictor, please contact Sierra support for more information.
