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arXiv · 1602.03419

Complexity of regular abstractions of one-counter languages

Mohamed Faouzi Atig·Dmitry Chistikov·Piotr Hofman·K Narayan Kumar·Prakash Saivasan·Georg Zetzsche
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Abstract

We study the computational and descriptional complexity of the following transformation: Given a one-counter automaton (OCA) A, construct a nondeterministic finite automaton (NFA) B that recognizes an abstraction of the language L(A): its (1) downward closure, (2) upward closure, or (3) Parikh image. For the Parikh image over a fixed alphabet and for the upward and downward closures, we find polynomial-time algorithms that compute such an NFA. For the Parikh image with the alphabet as part of the input, we find a quasi-polynomial time algorithm and prove a completeness result: we construct a sequence of OCA that admits a polynomial-time algorithm iff there is one for all OCA. For all three abstractions, it was previously unknown if appropriate NFA of sub-exponential size exist.

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Mohamed Faouzi Atig, Dmitry Chistikov, Piotr Hofman, K Narayan Kumar, Prakash Saivasan, Georg Zetzsche. 2016-02-10. Complexity of regular abstractions of one-counter languages. https://arxiv.org/abs/1602.03419

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