A probabilistic variant of input-driven pushdown automata (IDPDA), also known as visibly pushdown automata, is introduced. It is proved that these automata can be determinized: an n-state probabilistic IDPDA that accepts each string with probability at least λ+δ or at most λ-δ is transformed to a deterministic IDPDA with at most (1 + 1/δ)^(n² - n) states recognizing the same language. An asymptotically close lower bound is provided: for infinitely many n, there is a probabilistic IDPDA with 4n + 1 states and δ = 1/(270n), such that every equivalent deterministic IDPDA needs at least 7^(n²/14) states. A few special cases of automata with reduced determinization complexity are identified.
@InProceedings{rose_et_al:LIPIcs.MFCS.2023.78, author = {Rose, Alex and Okhotin, Alexander}, title = {{Probabilistic Input-Driven Pushdown Automata}}, booktitle = {48th International Symposium on Mathematical Foundations of Computer Science (MFCS 2023)}, pages = {78:1--78:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-292-1}, ISSN = {1868-8969}, year = {2023}, volume = {272}, editor = {Leroux, J\'{e}r\^{o}me and Lombardy, Sylvain and Peleg, David}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2023.78}, URN = {urn:nbn:de:0030-drops-186120}, doi = {10.4230/LIPIcs.MFCS.2023.78}, annote = {Keywords: Finite automata, probabilistic automata, input-driven automata, visibly pushdown automata, state complexity} }
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