Reachability in Two-Dimensional Unary Vector Addition Systems with States is NL-Complete
Blondin et al. showed at LICS 2015 that two-dimensional vector addition systems with states have reachability witnesses of length exponential in the number of states and polynomial in the norm of vectors. The resulting guess-and-verify algorithm is optimal (PSPACE), but only if the input vectors are...
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| Published in: | Proceedings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science pp. 477 - 484 |
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| Main Authors: | , , |
| Format: | Conference Proceeding |
| Language: | English |
| Published: |
New York, NY, USA
ACM
05.07.2016
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| Series: | ACM Conferences |
| ISBN: | 9781450343916, 1450343910 |
| Online Access: | Get full text |
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| Summary: | Blondin et al. showed at LICS 2015 that two-dimensional vector addition systems with states have reachability witnesses of length exponential in the number of states and polynomial in the norm of vectors. The resulting guess-and-verify algorithm is optimal (PSPACE), but only if the input vectors are given in binary. We answer positively the main question left open by their work, namely establish that reachability witnesses of pseudo-polynomial length always exist. Hence, when the input vectors are given in unary, the improved guess-and-verify algorithm requires only logarithmic space. |
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| ISBN: | 9781450343916 1450343910 |
| DOI: | 10.1145/2933575.2933577 |