Unambiguity in Logspace – a Survey
نویسنده
چکیده
The restriction of nondeterminism to unambiguous computations has been used as an attempt to clarify the relationship between deterministic and nondeterministic models of computation. In this paper we will consider three different, increasingly more restrictive notions of unambiguity. While all of them coincide for polynomial time bounded computation, this does not seem to happen for logarithmic space bounded computation. Moreover, the least restrictive class UL seems to coincide with NL (at least under a widely believed assumption) while the more restrictive classes StUL and RUL have a deterministic algorithm that runs in time log 2 n log log n . So in this paper we will give an overview over these classes and their relationship with deterministic and nondeterministic logspace.
منابع مشابه
Unambiguity and Fewness for Logarithmic Space 3 (preliminary Version, January 1991)
We consider various types of unambiguity for logarithmic space bounded Turing machines and polynomial time bounded log space auxiliary push-down automata. In particular, we introduce the notions of (general), reach, and strong unambiguity. We demonstrate that closure under complement of unambiguous classes implies equivalence of unambiguity and \unambiguous fewness". This, as we will show, appl...
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