.. _model-surrogate-multipoint:

""""""""""
multipoint
""""""""""


Construct a surrogate from multiple existing training points


.. toctree::
   :hidden:
   :maxdepth: 1

   model-surrogate-multipoint-tana
   model-surrogate-multipoint-qmea
   model-surrogate-multipoint-truth_model_pointer


**Specification**

- *Alias:* None

- *Arguments:* None


**Child Keywords:**

+-------------------------+--------------------+-------------------------+-----------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword          | Dakota Keyword Description                    |
|                         | Group              |                         |                                               |
+=========================+====================+=========================+===============================================+
| Required (Choose One)   | Multipoint         | `tana`__                | Local multi-point model via two-point         |
|                         | Surrogate          |                         | nonlinear approximation                       |
|                         |                    +-------------------------+-----------------------------------------------+
|                         |                    | `qmea`__                | Multi-point surrogate approximation based on  |
|                         |                    |                         | QMEA algorithm                                |
+-------------------------+--------------------+-------------------------+-----------------------------------------------+
| Required                                     | `truth_model_pointer`__ | Pointer to specify a "truth" model, from      |
|                                              |                         | which to construct a surrogate                |
+----------------------------------------------+-------------------------+-----------------------------------------------+

.. __: model-surrogate-multipoint-tana.html
__ model-surrogate-multipoint-qmea.html
__ model-surrogate-multipoint-truth_model_pointer.html



**Description**


Multipoint approximations use data from previous design points to
improve the accuracy of local approximations. The data often
comes from the current and previous iterates of a minimization algorithm.

Currently, only the
Two-point Adaptive Nonlinearity Approximation (TANA-3) method of
:cite:p:`Xu98` is supported with the ``tana`` keyword.

The
truth model to be used to generate the value/gradient data used in the
approximation is identified through the required
``truth_model_pointer`` specification.


