treedec is an open-source C++ library for computing tree decompositions of graphs. It provides a range of algorithms and heuristics for this task, as well as a preprocessing module that applies reduction rules to simplify the input graph before computation.

The library was developed by Felix Salfelder, Lukas Larisch, and Philipp Klaus Krause, former members of the group. It is used by the SDCC compiler suite for register allocation optimization.

In 2017, one of its exact algorithms won the first prize in the PACE challenge for exact treewidth computation.

Link to the treedec library: https://codeberg.org/freetdi/treedec.