.. _interface-analysis_drivers-fork:

""""
fork
""""


Launch analysis drivers using fork command


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

   interface-analysis_drivers-fork-parameters_file
   interface-analysis_drivers-fork-results_file
   interface-analysis_drivers-fork-file_tag
   interface-analysis_drivers-fork-file_save
   interface-analysis_drivers-fork-labeled
   interface-analysis_drivers-fork-aprepro
   interface-analysis_drivers-fork-work_directory
   interface-analysis_drivers-fork-allow_existing_results
   interface-analysis_drivers-fork-verbatim


**Specification**

- *Alias:* None

- *Arguments:* None


**Child Keywords:**

+-------------------------+--------------------+----------------------------+-----------------------------------------------+
| Required/Optional       | Description of     | Dakota Keyword             | Dakota Keyword Description                    |
|                         | Group              |                            |                                               |
+=========================+====================+============================+===============================================+
| Optional                                     | `parameters_file`__        | Specify the name of the parameters file       |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `results_file`__           | Specify the name of the results file          |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `file_tag`__               | Tag each parameters & results file name with  |
|                                              |                            | the function evaluation number                |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `file_save`__              | Keep the parameters & results files after the |
|                                              |                            | analysis driver completes                     |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `labeled`__                | Requires correct function value labels in     |
|                                              |                            | results file                                  |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `aprepro`__                | Write parameters files in APREPRO syntax      |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `work_directory`__         | Perform each function evaluation in a         |
|                                              |                            | separate working directory                    |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `allow_existing_results`__ | Change how Dakota deals with existing results |
|                                              |                            | files                                         |
+----------------------------------------------+----------------------------+-----------------------------------------------+
| Optional                                     | `verbatim`__               | Specify the command Dakota uses to launch     |
|                                              |                            | analysis driver(s) and filters                |
+----------------------------------------------+----------------------------+-----------------------------------------------+

.. __: interface-analysis_drivers-fork-parameters_file.html
__ interface-analysis_drivers-fork-results_file.html
__ interface-analysis_drivers-fork-file_tag.html
__ interface-analysis_drivers-fork-file_save.html
__ interface-analysis_drivers-fork-labeled.html
__ interface-analysis_drivers-fork-aprepro.html
__ interface-analysis_drivers-fork-work_directory.html
__ interface-analysis_drivers-fork-allow_existing_results.html
__ interface-analysis_drivers-fork-verbatim.html



**Description**


The ``fork`` interface is the most common means by which Dakota
launches a separate application analysis process.

The ``fork`` interface is recommended over ``system`` for most analysis
drivers that are external to Dakota, i.e., any driver not linked in
via the ``direct`` interface.

The parameters and results file names are passed on the command line
to the analysis driver(s).  If
input/output filters are specified, they will be run before/after the
analysis drivers.  The ``verbatim`` keyword is used to modify the
default driver/filter commands.

For additional information on invocation syntax, refer to :ref:`interfaces:sim`.



**Examples**


Spawn (fork) an external executable/script called 'rosenbrock' which
reads variables from params.in and writes responses to results.out.
Preserve the analysis files for each function evaluation with tag and
save.


.. code-block::

    interface
      analysis_drivers = 'rosenbrock'
        fork
          parameters_file = 'params.in'
          results_file   = 'results.out'
          file_tag
          file_save