,
Ismaël Jecker
,
Sławomir Lasota
,
Łukasz Orlikowski
Creative Commons Attribution 4.0 International license
The reachability problem in 3-dimensional vector addition systems with states (3-VASS) is known to be PSpace-hard, and to belong to Tower. We significantly narrow down the complexity gap by proving the problem to be solvable in doubly-exponential space. The result follows from a new upper bound on the length of the shortest path: if there is a path between two configurations of a 3-VASS then there is also one of at most triply-exponential length. We show it by introducing a novel technique of approximating the reachability sets of 2-VASS by small semi-linear sets.
@InProceedings{czerwinski_et_al:LIPIcs.ICALP.2025.153,
author = {Czerwi\'{n}ski, Wojciech and Jecker, Isma\"{e}l and Lasota, S{\l}awomir and Orlikowski, {\L}ukasz},
title = {{Reachability in 3-VASS Is Elementary}},
booktitle = {52nd International Colloquium on Automata, Languages, and Programming (ICALP 2025)},
pages = {153:1--153:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-372-0},
ISSN = {1868-8969},
year = {2025},
volume = {334},
editor = {Censor-Hillel, Keren and Grandoni, Fabrizio and Ouaknine, Jo\"{e}l and Puppis, Gabriele},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2025.153},
URN = {urn:nbn:de:0030-drops-235307},
doi = {10.4230/LIPIcs.ICALP.2025.153},
annote = {Keywords: vector addition systems, Petri nets, reachability problem, dimension three, doubly exponential space, length of shortest path}
}