.. _build-custom:

==================================
Building Custom Interactive Solver
==================================

If you are just starting with MFiX, you could use the :ref:`default solver
<running-default>` installed with MFiX. It is possible to run most of the
:ref:`tutorials` with the default solver.


However, for some cases you may want to use a custom mfixsolver.  When
running cases with UDFs (User Defined Functions, which are defined in Fortran
source files in the project directory), it is necessary to build a custom
solver. A custom solver is an ``mfixsolver`` executable built in the project
directory, specific to that project.


.. _build-custom-gui:

Custom Solver From GUI
----------------------

Press the |build| (Build) button to display the Build dialog box. Select
appropriate compilation options, then press the "Build Solver" button. It may take a few
minutes to compile. See :ref:`build-dialog` for further details about
compilation options. The "Build Command" of the build dialog will show the
equivalent command for :ref:`build-custom`.

After building the custom solver, run a simulation by pressing |play| (Run) to
display the :ref:`run-dialog`. Select the mfixsolver file you have just built.

You can pause, unpause, stop, or get info from the solver.


.. _build-custom-cmdline:

Custom solver from command line
-------------------------------

For example, the ``tfm/silane_pyrolysis_2d`` tutorial has UDFs and will not run with the
default solver.

.. code-block:: shell-session

    $ cd tutorials/tfm/silane_pyrolysis_2d/
    $ ls
    SP2D.mfx  usr0.f  usr1.f  usr_mod.f  usr_rates.f

To build a custom solver for ``tfm/silane_pyrolysis_2d``:

.. code-block:: shell-session

    $ build_mfixsolver
    ...build output...
    $ ls
    build/ lib/ mfixsolver  mfixsolver.so SP2D.mfx  usr0.f  usr0.o usr1.f  usr_mod.f  usr_rates.f

The ``build_mfixsolver`` command creates a wrapper script
``mfixsolver``, that runs the case-specific MFiX solver (``mfixsolver.so``).

The ``build`` directory can be deleted, and the custom ``mfixsolver``
will still run. However, leaving the ``build`` directory will greatly
speed up rebuilds if you want to edit the UDFs and run
``build_mfixsolver`` again.

.. include:: /icons.rst