Published: Sep 20, 2024 by Peter Hill
Project info
MacauFOAM is an extension for OpenFOAM for simulating low-temperature plasmas using the particle-in-cell (PIC) method. The code has been used in several publications, and unfortunately is currently closed-source due to the institutional policies.
As usual, we started with our health check, reviewing the project’s codebase, documentation, tests, and so on. This turned out to be a bit unusual – while there were design choices for the project layout and some code constructions that I would definitely argue against in most C++ projects, actually these were following the OpenFOAM style very closely, and so I ended up rating the project reasonably healthy. OpenFOAM is a big project with many users, so restructuring this code and rewriting in a more conventional modern C++ style would both be a significant effort, and could end up being a net negative.
There were two small pieces of work we agreed with the project lead though, the first one being to replace their pseudo-random number generator (PRNG) with something more robust. The existing implementation used the C++ standard library PRNG Mersenne-Twister, which has many issues when used for Monte-Carlo simulations (such as in PIC!). A very good modern PRNG is xoshiro, and it was very simple to adapt this to the C++ PRNG framework, and drop it in to MacauFOAM.
The second piece of work was to get CI up and running for them. The software repository is on an institution-hosted GitLab instance, so this was not quite as simple as setting it up for public GitHub repos, as it involved getting a VM setup as a runner, and some manual intervention. After the usual back-and-forth involved in setting up CI on new projects, the code and now builds and runs the existing smoke tests in a VM with OpenFOAM pre-installed.