Installing PICI-LIGGGHTS

A step-by-step guide with video, instructions and commands for installing PICI-LIGGGHTS with high level Python interface CoExSiST on Ubuntu 20.04. Note: This doesn’t work on Ubuntu 22.04 so make sure to use Ubuntu 20.04. If you don’t have a computer running Ubuntu I would recommend using a VM software such as VirtualBox to set up an Ubuntu VM.

Firstly, download a clone of the PICI-LIGGGHTS zip from GitHub found here.
Extract the zip file and move to your location of choice.
Install build-essential to install everything required for compiling basic C and C++ software.
```
sudo apt install build-essential
```
Install libboost-dev for additional C++ source libraries (Prevents some errors when compiling PICI-LIGGGHTS).
```
sudo apt install libboost-dev
```
Install CMake that can be used to automatically build PICI-LIGGGHTS for us later.
```
sudo snap install cmake --classic
```
Install Open MPI, an open source MPI to allow PICI-LIGGGHTS to make use of parallelisation.
```
sudo apt install openmpi-bin
```
Go to the extracted PICI-LIGGGHTS master folder and make build folder inside.
```
mkdir build && cd build
```

Once inside the build folder run the CMake command to make the CMake files.

cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-O3 -march=native -fPIC" ../src/

Once CMake is finished, run the ‘make’ command to start building PICI-LIGGGHTS. (This may take some time)
```
make -j4
```
Copy ‘libliggghts.so’ to a standard location.
```
sudo cp libliggghts.so /usr/local/lib
```

Copy liggghts.py to the Python packages location.

cd ..
cd python
sudo cp liggghts.py /usr/local/lib/python3.8/dist-packages/

Add /usr/local/lib to library path in the .bashrc file.

nano ~/.bashrc
LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH

A simple Python interface of PICI-LIGGGHTS should now be able to be run from Python. It is a good idea to test at this point if it works.
1. Optional: Test PICI-LIGGGHTS works in Python: Install idle (Or your text editor/IDE of choice)
```
sudo apt install idle
```
2. Run idle
```
idle
```
3. Type Python lines to import PICI-LIGGGHTS and start liggghts object.
```
from liggghts import liggghts
liggghts()
```
To use the high level Python interface we need to install the Python package CoExSiST. To do this we need the Python package manager pip.
```
sudo apt install pip
```
Install CoExSiST Python package.
```
pip install coexist
```
All done! PICI-LIGGGHTS and CoExSiST are installed. Check CoExSiST works by opening your text editor/IDE of choice and importing coexist to make sure no errors occur.
```
import coexist
```