A parallel extended GCD algorithm

  • Authors:
  • Sidi Mohamed Sedjelmaci

  • Affiliations:
  • LIPN CNRS UMR 7030, Université Paris-Nord, 99 Avenue J.B. Clément, 93430 Villetaneuse, France

  • Venue:
  • Journal of Discrete Algorithms
  • Year:
  • 2008

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Abstract

A new parallel extended GCD algorithm is proposed. It matches the best existing parallel integer GCD algorithms of Sorenson and Chor and Goldreich, since it can be achieved in O"@e(n/logn) time using at most n^1^+^@e processors on CRCW PRAM. Sorenson and Chor and Goldreich both use a modular approach which consider the least significant bits. By contrast, our algorithm only deals with the leading bits of the integers u and v, with u=v. This approach is more suitable for extended GCD algorithms since the coefficients of the extended version a and b, such that au+bv=gcd(u,v), are deeply linked with the order of magnitude of the rational v/u and its continuants. Consequently, the computation of such coefficients is much easier.