PACE Solver Description: Bute-Plus: A Bottom-Up Exact Solver for Treedepth

Abstract

This note introduces Bute-Plus, an exact solver for the treedepth problem. The core of the solver is a positive-instance driven dynamic program that constructs an elimination tree of minimum depth in a bottom-up fashion. Three features greatly improve the algorithm's run time. The first of these is a specialised trie data structure. The second is a domination rule. The third is a heuristic presolve step can quickly find a treedepth decomposition of optimal depth for many instances.Comment: 4 pages, 1 appendix pages, 0 figures. A version of this tool description paper without the appendix is published in the proceedings of IPEC 2020: https://drops.dagstuhl.de/opus/volltexte/2020/13337/pdf/LIPIcs-IPEC-2020-34.pdf . Changes: this version expands the paper from a preliminary versio