.. _model-active_subspace-truncation_method:

"""""""""""""""""
truncation_method
"""""""""""""""""


Metric that estimates active subspace size


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

   model-active_subspace-truncation_method-bing_li
   model-active_subspace-truncation_method-constantine
   model-active_subspace-truncation_method-energy
   model-active_subspace-truncation_method-cross_validation


**Specification**

- *Alias:* None

- *Arguments:* None

- *Default:* constantine


**Child Keywords:**

+-------------------------+--------------------+----------------------+-----------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword       | Dakota Keyword Description                    |
|                         | Group              |                      |                                               |
+=========================+====================+======================+===============================================+
| Optional                                     | `bing_li`__          | Use the Bing Li "ladle" diagnostic to         |
|                                              |                      | truncate subspace                             |
+----------------------------------------------+----------------------+-----------------------------------------------+
| Optional                                     | `constantine`__      | Use the Constantine diagnostic to truncate    |
|                                              |                      | subspace                                      |
+----------------------------------------------+----------------------+-----------------------------------------------+
| Optional                                     | `energy`__           | Truncate the subspace based on eigenvalue     |
|                                              |                      | energy                                        |
+----------------------------------------------+----------------------+-----------------------------------------------+
| Optional                                     | `cross_validation`__ | Truncate the subspace to minimize surrogate   |
|                                              |                      | cross-validation error                        |
+----------------------------------------------+----------------------+-----------------------------------------------+

.. __: model-active_subspace-truncation_method-bing_li.html
__ model-active_subspace-truncation_method-constantine.html
__ model-active_subspace-truncation_method-energy.html
__ model-active_subspace-truncation_method-cross_validation.html



**Description**


Metric that controls how many basis vectors are retained in the active
subspace.

*Default Behavior*

The default is to use the
:dakkw:`model-active_subspace-truncation_method-constantine` diagnostic.

*Usage Tips*

If the automated subspace identification methods do not yield desirable results,
consider using the explicit :dakkw:`model-active_subspace-dimension` truncation option.