#+TITLE: BTCSDiffusion

#+BEGIN_CENTER
A framework solving diffusion problems using BTCS approach.
#+END_CENTER

* About

This project aims to provide a library for solving diffusion problems using the
backward Euler method (BTCS) implemented in C++.

The library is built on top of [[https://eigen.tuxfamily.org/index.php?title=Main_Page][Eigen]], providing easy access to data structures
and the linear equation solver.

We designed the API to be as much flexible as possible. Nearly every built-in,
framework or third-party data structure can be used to model a problem, as long
a pointer to continious memory can be providided.

Also we provide basic parallelization by using [[https://www.openmp.org/][OpenMP]], which can be easily
turned on/off during generation of makefiles.

At the current state, only 1D diffusion problems on a regular grid can be solved
reliably. The 2D solution is already implemented, but still returns wrong
values. This will be fixed in the future.

* Getting started

As this diffusion module is designed as a framework library and makefile
generation is done by [[https://cmake.org/][CMake]], you're good to go to also use CMake as your build
toolkit. If you decide to not use CMake, you need to manually link your
application/library to BTCSDiffusion.

1. Create project directory.

   #+BEGIN_SRC
   $ mkdir sample_project && cd sample_project
   #+END_SRC

2. Clone this repository into path of choice project directory

   #+BEGIN_SRC
   $ git clone git@git.gfz-potsdam.de:mluebke/diffusion.git
   #+END_SRC

3. Add the following line into =CMakeLists.txt= file:

   #+BEGIN_SRC
   add_subdirectory(path_to_diffusion_module EXCLUDE_FROM_ALL)
   #+END_SRC

4. Write application/library using API of =BTCSDiffusion=.

5. Link target application/library against =BTCSDiffusion=. Do this by adding
   into according =CMakeLists.txt= file:

   #+BEGIN_SRC
   target_link_libraries(your_libapp BTCSDiffusion)
   #+END_SRC

6. Build your application/library with CMake.


* Usage

Setting up an enviroment to use the =BTCSDiffusion= module is divided into the
following steps:

1. Defining dimension of diffusion problem.
2. Set grid sizes in according dimensions.
3. Set the timestep to simulate.
4. Defining boundary conditions.
5. Run the simulation!

This will run a simulation on the defined grid for one species. See the source
code documentation of =BTCSDiffusion= and the examples in the =app/= directory
for more information.

* Roadmap

- [X] 1D diffusion
- [ ] 2D diffusion
- [ ] 3D diffusion (?)
- [ ] R-API
- [ ] Python-API (?)
- [ ] Testing

* License
TODO?