.. _method-ncsu_direct:

"""""""""""
ncsu_direct
"""""""""""


DIviding RECTangles method



**Topics**


global_optimization_methods


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

   method-ncsu_direct-solution_target
   method-ncsu_direct-min_boxsize_limit
   method-ncsu_direct-volume_boxsize_limit
   method-ncsu_direct-convergence_tolerance
   method-ncsu_direct-max_iterations
   method-ncsu_direct-max_function_evaluations
   method-ncsu_direct-scaling
   method-ncsu_direct-model_pointer


**Specification**

- *Alias:* None

- *Arguments:* None


**Child Keywords:**

+-------------------------+--------------------+------------------------------+---------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword               | Dakota Keyword Description                  |
|                         | Group              |                              |                                             |
+=========================+====================+==============================+=============================================+
| Optional                                     | `solution_target`__          | Specifies a globally optimal value toward   |
|                                              |                              | which the optimizer should track            |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `min_boxsize_limit`__        | Stopping Criterion based on shortest edge   |
|                                              |                              | of hyperrectangle                           |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `volume_boxsize_limit`__     | Stopping criterion based on volume of       |
|                                              |                              | search space                                |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `convergence_tolerance`__    | Stopping criterion based on objective       |
|                                              |                              | function or statistics convergence          |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `max_iterations`__           | Number of iterations allowed for optimizers |
|                                              |                              | and adaptive UQ methods                     |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `max_function_evaluations`__ | Number of function evaluations allowed for  |
|                                              |                              | optimizers                                  |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `scaling`__                  | Turn on scaling for variables, responses,   |
|                                              |                              | and constraints                             |
+----------------------------------------------+------------------------------+---------------------------------------------+
| Optional                                     | `model_pointer`__            | Identifier for model block to be used by a  |
|                                              |                              | method                                      |
+----------------------------------------------+------------------------------+---------------------------------------------+

.. __: method-ncsu_direct-solution_target.html
__ method-ncsu_direct-min_boxsize_limit.html
__ method-ncsu_direct-volume_boxsize_limit.html
__ method-ncsu_direct-convergence_tolerance.html
__ method-ncsu_direct-max_iterations.html
__ method-ncsu_direct-max_function_evaluations.html
__ method-ncsu_direct-scaling.html
__ method-ncsu_direct-model_pointer.html



**Description**


North Carolina State University (NCSU) has an implementation of the
DIRECT algorithm (DIviding RECTangles algorithm that is outlined in
the SCOLIB method section above). This version is documented in
:cite:p:`Gab01` We have found that the NCSU DIRECT
implementation works better and is more robust for some problems than
``coliny_direct``. Currently, we maintain both versions of DIRECT in
Dakota; in the future, we may deprecate one.

The NCSU DIRECT method is selected with ``ncsu_direct``. We have tried
to maintain consistency between the keywords in SCOLIB and NCSU
implementation of DIRECT, but the algorithms have different
parameters, so the keywords sometimes have slightly different meaning.

*Stopping Criteria*

The algorithm stops based on:


- :dakkw:`method-ncsu_direct-max_iterations` - number of iterations
- :dakkw:`method-ncsu_direct-max_function_evaluations` - number of function evaluations
- :dakkw:`method-ncsu_direct-solution_target` and :dakkw:`method-ncsu_direct-convergence_tolerance`
- :dakkw:`method-ncsu_direct-min_boxsize_limit`
- :dakkw:`method-ncsu_direct-volume_boxsize_limit`

This method will always strictly respect the number of iterations, but
may slightly exceed the number of function evaluations, as it will
always explore all sub-rectangles at the current level.


*Expected HDF5 Output*

If Dakota was built with HDF5 support and run with the
:dakkw:`environment-results_output-hdf5` keyword, this method
writes the following results to HDF5:


- :ref:`hdf5_results-best_params`
- :ref:`hdf5_results-best_obj_fncs` (when :dakkw:`responses-objective_functions`) are specified)
- :ref:`hdf5_results-best_constraints`
- :ref:`hdf5_results-calibration` (when :dakkw:`responses-calibration_terms` are specified)