# Welcome to Dionysus 2 documentation!¶

Dionysus 2 is the second incarnation of the library for computing persistent homology. As before, it’s written in C++, with Python bindings. The second version is re-written from scratch, which helps it accomplish a few goals:

• Modified BSD license (because GPL causes too many problems in academic software).
• No dependency on Boost.Python; Dionysus 2 uses (and includes) PyBind11 instead, which greatly simplifies installation.
• Cleaner, more consistent internal design (for example, all algorithms support arbitrary fields).
• Some new algorithms, e.g., Omni-field Persistence and Wasserstein and bottleneck distance computation from Hera.
• A few Plotting routines, based on Matplotlib.
• Better integration with NumPy.

Features that haven’t (yet) made it over from Dionysus 1 include vineyards. Alpha shape filtrations are available via DioDe.

Dependencies:
Requirements:
• Boost needs to be at least version 1.55.
• If you are using GCC, the oldest supported version is 5.4.
Contact:
• please use the dionysus mailing list for all questions and discussion related to the library;
• GitHub’s issue tracker is a central location for bug reports and feature requests.

## Get, Build, Install¶

The simplest way to install Dionysus, as a Python package, is from PyPI:

pip install --verbose dionysus


Pass --upgrade to pip, if you have already installed some version of Dionysus.

Alternatively, you can install it directly from the development repository (this gives you the latest version):

pip install --verbose git+https://github.com/mrzv/dionysus.git


Alternatively, you can clone and build everything by hand. To get Dionysus 2, either clone its repository:

git clone https://github.com/mrzv/dionysus.git


To build the project:

mkdir build
cd build
cmake ..
make


To use the Python bindings, either launch Python from .../build/bindings/python or add this directory to your PYTHONPATH variable, by adding:

export PYTHONPATH=.../build/bindings/python:\$PYTHONPATH


to your ~/.bashrc or ~/.zshrc.