## Michael Blondin ; Christoph Haase ; Filip Mazowiecki ; Mikhail Raskin - Affine Extensions of Integer Vector Addition Systems with States

lmcs:5797 - Logical Methods in Computer Science, July 20, 2021, Volume 17, Issue 3 - https://doi.org/10.46298/lmcs-17(3:1)2021
Affine Extensions of Integer Vector Addition Systems with States

Authors: Michael Blondin ; Christoph Haase ; Filip Mazowiecki ; Mikhail Raskin

We study the reachability problem for affine $\mathbb{Z}$-VASS, which are integer vector addition systems with states in which transitions perform affine transformations on the counters. This problem is easily seen to be undecidable in general, and we therefore restrict ourselves to affine $\mathbb{Z}$-VASS with the finite-monoid property (afmp-$\mathbb{Z}$-VASS). The latter have the property that the monoid generated by the matrices appearing in their affine transformations is finite. The class of afmp-$\mathbb{Z}$-VASS encompasses classical operations of counter machines such as resets, permutations, transfers and copies. We show that reachability in an afmp-$\mathbb{Z}$-VASS reduces to reachability in a $\mathbb{Z}$-VASS whose control-states grow linearly in the size of the matrix monoid. Our construction shows that reachability relations of afmp-$\mathbb{Z}$-VASS are semilinear, and in particular enables us to show that reachability in $\mathbb{Z}$-VASS with transfers and $\mathbb{Z}$-VASS with copies is PSPACE-complete. We then focus on the reachability problem for affine $\mathbb{Z}$-VASS with monogenic monoids: (possibly infinite) matrix monoids generated by a single matrix. We show that, in a particular case, the reachability problem is decidable for this class, disproving a conjecture about affine $\mathbb{Z}$-VASS with infinite matrix monoids we raised in a preliminary version of this paper. We complement this result by presenting an affine $\mathbb{Z}$-VASS with monogenic matrix monoid and undecidable reachability relation.

Volume: Volume 17, Issue 3
Published on: July 20, 2021
Accepted on: July 2, 2021
Submitted on: September 30, 2019
Keywords: Computer Science - Logic in Computer Science,Computer Science - Computational Complexity