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Multiple GCDs. probabilistic analysis of the plain algorithm

Published: 26 June 2013 Publication History
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  • Abstract

    This paper provides a probabilistic analysis of an algorithm which computes the gcd of ℓ inputs (with ℓ ≥ 2), with a succession of ℓ - 1 phases, each of them being the Euclid algorithm on two entries. This algorithm is both basic and natural, and two kinds of inputs are studied: polynomials over the finite field Fq and integers. The analysis exhibits the precise probabilistic behaviour of the main parameters, namely the number of iterations in each phase and the evolution of the length of the current gcd along the execution. We first provide an average-case analysis. Then we make it even more precise by a distributional analysis. Our results rigorously exhibit two phenomena: (i) there is a strong difference between the first phase, where most of the computations are done and the remaining phases; (ii) there is a strong similarity between the polynomial and integer cases, as can be expected.

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    1. Multiple GCDs. probabilistic analysis of the plain algorithm

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      cover image ACM Conferences
      ISSAC '13: Proceedings of the 38th International Symposium on Symbolic and Algebraic Computation
      June 2013
      400 pages
      ISBN:9781450320597
      DOI:10.1145/2465506
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      Published: 26 June 2013

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      Author Tags

      1. analytic combinatorics
      2. average-case analysis
      3. dynamical analysis
      4. gcd algorithms
      5. generating functions

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