Arithmetic with real algebraic numbers is in NC

  • Authors:
  • B. Mishra;P. Pedersen

  • Affiliations:
  • New York University;New York University

  • Venue:
  • ISSAC '90 Proceedings of the international symposium on Symbolic and algebraic computation
  • Year:
  • 1990

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Abstract

We describe NC algorithms for doing exact arithmetic with real algebraic numbers in the sign-coded representation introduced by Coste and Roy [CoR 1988]. We present polynomial sized circuits of depth &Ogr;(log3 N) for the monadic operations -&agr;, 1/&agr;, as well as &agr; + r, &agr; · r, and sgn(&agr; - r), where r is rational and &agr; is real algebraic. We also present polynomial sized circuits of depth &Ogr;(log7 N) for the dyadic operations &agr;+&bgr;, &agr;·&bgr;, and sgn(&agr; - &bgr;), where &agr; and &bgr; are both real algebraic. Our algorithms employ a strengthened form of the NC polynomial-consistency algorithm of Ben-Or, Kozen, and Reif [BKR 1986].