eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2020-08-26
38:1
38:20
10.4230/LIPIcs.CONCUR.2020.38
article
Coverability in 1-VASS with Disequality Tests
Almagor, Shaull
1
https://orcid.org/0000-0001-9021-1175
Cohen, Nathann
2
Pérez, Guillermo A.
3
https://orcid.org/0000-0002-1200-4952
Shirmohammadi, Mahsa
4
Worrell, James
5
Technion - Israel Institute of Technology, Haifa, Israel
CNRS & LRI, Gif-sur-Yvette, France
University of Antwerp, Belgium
CNRS & IRIF, Université de Paris, France
University of Oxford, UK
We study a class of reachability problems in weighted graphs with constraints on the accumulated weight of paths. The problems we study can equivalently be formulated in the model of vector addition systems with states (VASS). We consider a version of the vertex-to-vertex reachability problem in which the accumulated weight of a path is required always to be non-negative. This is equivalent to the so-called control-state reachability problem (also called the coverability problem) for 1-dimensional VASS. We show that this problem lies in NC: the class of problems solvable in polylogarithmic parallel time. In our main result we generalise the problem to allow disequality constraints on edges (i.e., we allow edges to be disabled if the accumulated weight is equal to a specific value). We show that in this case the vertex-to-vertex reachability problem is solvable in polynomial time even though a shortest path may have exponential length. In the language of VASS this means that control-state reachability is in polynomial time for 1-dimensional VASS with disequality tests.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol171-concur2020/LIPIcs.CONCUR.2020.38/LIPIcs.CONCUR.2020.38.pdf
Reachability
Vector addition systems with states
Weighted graphs