I started developing the Hierarchy of Parameters in 2022. Initially in Python, the first version was deployed somewhat fast. However, with time the complexity of the project grew as well so I decided to rewrite HOPS to Rust – using this opportunity to learn the language.

Currently, you can find more information about HOPS on its own website ↗. Here, I would like to give a more personal viewpoint on the project.

Why make the project

The idea for HOPS was in the air for years. During my Ph.D. studies at CTU, we would study a problem and inevitably the questions about pushing results to further parameters would arise. Having a more complete overview of the hierarchy would have been quite useful.

We were not the only ones that stumbled upon this idea. Already in 2012 M. Sorge ↗ started to put together a document ↗ with parameters and their relations. This overview is quite nice, kept in a repository ↗, and served as a starting points for many later projects.

In 2015-03-26 ISGCI ↗ added some support for graph parameters. There, source of the information were compilations (theses) of Sasák ↗ and Spiess.

What HOPS offers now

The current state of HOPS has much to be desired. The good parts include – rough overview of the known parameters, interactable diagrams, ability to add detailed information about relations that references proved, clear picture of what is known or missing in HOPS. The bad parts are – missing relations due to a small number of sources, missing API (only simplified is available), limited interaction with the community.