Rheinische Friedrich-Wilhelms-Universität Bonn Institut für Informatik
 
Abteilung V

 
Universität Bonn -> Institut für Informatik -> Abteilung V
CS-Reports 1985-1989 Copyright 1985-1989 Universität Bonn, Institut für Informatik, Abt. V
853

There is No Polynomial Deterministic Space Simulation of Two-Way Probabilistic Space with a Two-Way Random-Tape Generator
Marek Karpinski and Rutger Verbeek
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We prove there is no polynomial deterministic space simulation for two-way random-tape probabilistic space (Pr$_2$SPACE) (as defined in \cite{BCP83}) for all functions $f : \: \NN \rightarrow \NN$ and all $\alpha \in \NN, \, \prtwospace(f(n)) \not\subseteq \dspace(f(n)^{\alpha})$. This is answer to the problem formulated in op cit., whether the deterministic squared-space simulation (for recognizers and transducers) generalizes to the two-way random-tape machine model. We prove, in fact, a stronger result saying that even space-bounded Las~Vegas two-way random-tape algorithms (yielding always the correct answer and terminating with probability 1) are exponentially more efficient than the deterministic ones.

Last Change: 11/25/08 at 14:41:44
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Universität Bonn -> Institut für Informatik -> Abteilung V

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