.. include:: ../mydefs.rst

2D SWE: default LSPG
====================

- ROM technique: basic LSPG

- problem: `2D shallow water equations (SWE) <https://pressio.github.io/pressio-demoapps/swe_2d.html>`_


Prerequisites
-------------

- A valid build of the tutorials, see `here <../build.html>`__,

- The following env variables MUST be set:

  .. code-block:: bash

     export REPOSRC=<full-path-to-the-pressio-tutorials-source-repo>/end-to-end-roms
     export BUILDDIR=<full-path-to-where-you-built-the-tutorials>

.. admonition:: To run the demo scripts below, you MUST be inside the correct directory:
   :class: important

   .. code-block:: bash

      cd $BUILDDIR/end-to-end-roms/2d_swe_lspg_default


Workflow File
-------------

The `workflow file <../../../end-to-end-roms/2d_swe_lspg_default/wf.yaml>`_
for this demo is shown below for exposition purposes, but it is automatically
copied to the build directory, so you don't need to do anything:

.. literalinclude:: ../../../end-to-end-roms/2d_swe_lspg_default/wf.yaml
   :language: yaml
   :lines: 1-35
   :linenos:


Step 1: execute FOMs
--------------------

.. code-block:: bash

   # from within $BUILDDIR/end-to-end-roms/2d_swe_lspg_default
   python3 $REPOSRC/wf_foms.py --wf wf.yaml

.. warning::

   This might take a few mins to run, be patient!

..
   When we run the FOM driver, the following C++ code is being executed:

   .. literalinclude:: ../../../end-to-end-roms/cpp/run_fom_implicit.hpp
      :language: cpp
      :lines: 56-90

At the end, doing ``tree -L 1 .`` should produce:

.. code-block:: bash

   .
   ├── CMakeFiles
   ├── Makefile
   ├── cmake_install.cmake
   ├── fom_mesh
   ├── fom_test_runid_0
   ├── fom_train_runid_0
   ├── fom_train_runid_1
   ├── plot.py
   └── wf.yaml

Step 2: offline rom
-------------------

.. code-block:: bash

   # from within $BUILDDIR/end-to-end-roms/2d_swe_lspg_default
   python3 $REPOSRC/wf_offline_rom.py --wf wf.yaml

The offline rom takes care of using the FOM training data to compute the POD modes,
and creates all data into an "offline_rom" subdirectory:

.. code-block:: bash

   ./offline_rom/
   ├── pod_input.yaml
   ├── state_left_singular_vectors.bin
   ├── state_singular_values.txt
   └── state_snapshots.bin


Step 3: lspg rom
----------------

.. code-block:: bash

   # from within $BUILDDIR/end-to-end-roms/2d_swe_lspg_default
   python3 $REPOSRC/wf_lspg.py --wf wf.yaml

..
   The following C++ code is being executed:

   .. literalinclude:: ../../../end-to-end-roms/cpp/run_default_lspg.hpp
      :language: cpp
      :lines: 58-82

   .. literalinclude:: ../../../end-to-end-roms/cpp/lspg_pick_solver_and_run.hpp
      :language: cpp
      :lines: 52-64, 67-78, 111

At the end, you should have the following directory structure:

.. code-block:: bash

   .
   ├── CMakeFiles
   ├── Makefile
   ├── cmake_install.cmake
   ├── default_lspg_truncation_energybased_99.99999_runid_0
   ├── default_lspg_truncation_energybased_99.999_runid_0
   ├── fom_mesh
   ├── fom_test_runid_0
   ├── fom_train_runid_0
   ├── fom_train_runid_1
   ├── offline_rom
   ├── plot.py
   └── wf.yaml

Step 4: process results
-----------------------

.. code-block:: bash

   # from within $BUILDDIR/end-to-end-roms/2d_swe_lspg_default
   python3 $REPOSRC/wf_reconstruct_on_full_mesh.py
   python3 plot.py

.. image:: ../../../end-to-end-roms/2d_swe_lspg_default/FOM.png
  :width: 32 %
  :alt: FOM
.. image:: ../../../end-to-end-roms/2d_swe_lspg_default/ROM_18.png
  :width: 32 %
  :alt: ROM, 22 modes
.. image:: ../../../end-to-end-roms/2d_swe_lspg_default/ROM_36.png
  :width: 32 %
  :alt: ROM, 55 modes