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Mathematical systems theory

, Volume 28, Issue 2, pp 117–140 | Cite as

Adaptive logspace reducibility and parallel time

  • C. Àlvarez
  • J. L. Balcázar
  • B. Jenner
Article

Abstract

We discuss two notions of functional oracle for logarithmic space-bounded machines, which differ in whether there is only one oracle tape for both the query and the answer or a separate tape for the answer, which can still be read while the next query is already being constructed. The first notion turns out to be basically nonadaptive, behaving like access to an oracle set. The second notion, on the other hand, is adaptive. By imposing appropriate bounds on the number of functional oracle queries made in this computation model, we obtain new characterizations of the NC and AC hierarchies; thus the number of oracle queries can be considered as a measure of parallel time. Using this characterization of parallel classes, we solve open questions of Wilson.

Keywords

Computation Model Computational Mathematic Parallel Classis Parallel Time Oracle Query 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • C. Àlvarez
    • 1
  • J. L. Balcázar
    • 1
  • B. Jenner
    • 2
  1. 1.Department of Software (Llenguatges i Sistemes Informàtics)Universitat Politècnica de CatalunyaBarcelonaSpain
  2. 2.Fakultät für InformatikTechnische Universität MünchenMünchenGermany

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