Counting paths in VPA Is complete for #NC1

  • Authors:
  • Andreas Krebs;Nutan Limaye;Meena Mahajan

  • Affiliations:
  • University of Tübingen, Germany;Tata Institute of Fundamental Research, Mumbai, India;The Institute of Mathematical Sciences, Chennai, India

  • Venue:
  • COCOON'10 Proceedings of the 16th annual international conference on Computing and combinatorics
  • Year:
  • 2010

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Abstract

We give a #NC1 upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton. Our algorithm involves a non-trivial adaptation of the arithmetic formula evaluation algorithm of Buss, Cook, Gupta, Ramachandran ([9]). We also show that the problem is #NC1 hard. Our results show that the difference between #BWBP and #NC1 is captured exactly by the addition of a visible stack to a nondeterministic finite-state automata.