Compiling WRF-GC
=================

This section discusses:

* Configuring WRF compile.
* **Installing the GEOS-Chem species into WRF.**
* Compiling WRF-GC.
* Compiling :term:`WPS`.

Configuring WRF compile
------------------------

Go to the ``WRF`` folder.

**If you are using WRF version 3:**

.. code-block::

	./configure -hyb

**If you are using WRF version 4 or above:**

.. code-block::

	./configure

Select the compiler option corresponding to your environment, and select the **(dmpar) option**. e.g., Intel compiler, icc, ifort, (dmpar). dmpar is required and means distributed-memory parallel, which uses MPI and is used by WRF-GC.

For nesting option, select 1 = basic. Other nesting options are unsupported.

Installing the GEOS-Chem species into WRF
------------------------------------------

.. warning::
	This step is **crucial**. If this step is not performed, you will have to start this page over and waste hours of your time.

Go to the ``WRF/chem`` folder and run ``make install_registry``.

If this step shows an error, make sure you did download WRF-GC into ``WRF/chem`` folder. It should look like this:

.. code-block::

	WRF/chem$ ls
	chem_driver.F 		Makefile 		gc 		config 
	wrfgc_convert_state_mod.F ...

.. note::
	Starting in WRF-GC 3.0, similar to the out-of-box setup of the GEOS-Chem offline chemical transport model, the setup process will request some information about you for use statistic purposes. Even if you are a long-term WRF-GC and/or GEOS-Chem user, we ask that you help answer these questions to help us keep an accurate count of WRF-GC users.

Compiling WRF-GC
----------------

Go back to the ``WRF`` folder and run:

.. code-block::

	./compile em_real

Wait patiently. The process may take up to 2 - 4 hours depending on your system. If you encounter errors, note them down. A list of common errors is available at :doc:`/common-errors`.

When successful, the output looks like

.. code-block::

	==========================================================================
	build started:   Sun Apr 15 12:00:00 CST 2018
	build completed: Sun Apr 15 13:00:00 CST 2018
	--->                  Executables successfully built                  <---
	-rwxrwxr-x 1 hplin hplin 63670720 Apr 15 05:34 main/ndown.exe
	-rwxrwxr-x 1 hplin hplin 63753008 Apr 15 05:35 main/real.exe
	-rwxrwxr-x 1 hplin hplin 62683008 Apr 15 05:34 main/tc.exe
	-rwxrwxr-x 1 hplin hplin 71153896 Apr 15 05:34 main/wrf.exe
	==========================================================================


Compiling WPS
--------------

1. Go one level up and then into the ``WPS`` folder.
2. Run ``./configure``.
3. Run ``./compile``.

If you encounter errors, note them down. A list of common errors is available at :doc:`/common-errors`.

Compiling after code changes
----------------------------

To recompile WRF after changing code, you can just run

.. code-block::

    ./compile em_real

Again in the WRF root directory.

**If you have changed the species list** (``registry.chem``), in which case you will have to clean everything and rebuild:

.. code-block::

	./clean -a
	./compile em_real