Nearly Optimal Refinement of Real Roots of a Univariate Polynomial - Inria - Institut national de recherche en sciences et technologies du numérique
Article Dans Une Revue Journal of Symbolic Computation Année : 2016

Nearly Optimal Refinement of Real Roots of a Univariate Polynomial

Résumé

We assume that a real square-free polynomial A has a degree d, a maximum coefficient bitsize τ and a real root lying in an isolating interval and having no nonreal roots nearby (we quantify this assumption). Then we combine the Double Exponential Sieve algorithm (also called the Bisection of the Exponents ), the bisection, and Newton iteration to decrease the width of this inclusion interval by a factor of $t=2^{−L}$. The algorithm has Boolean complexity View the MathML source $O_B(d^2 \tau +d L)$. This substantially decreases the known bound View the MathML source $O_B(d^3+d^2 L)$ and is optimal up to a polylogarithmic factor. Furthermore we readily extend our algorithm to support the same upper bound on the complexity of the refinement of $r$ real roots, for any $r \leq d$, by incorporating the known efficient algorithms for multipoint polynomial evaluation. The main ingredient for the latter is an efficient algorithm for (approximate) polynomial division; we present a variation based on structured matrix computation with quasi-optimal Boolean complexity.
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Dates et versions

hal-00960896 , version 1 (19-03-2014)
hal-00960896 , version 2 (28-12-2015)

Identifiants

  • HAL Id : hal-00960896 , version 1

Citer

Victor Y. Pan, Elias Tsigaridas. Nearly Optimal Refinement of Real Roots of a Univariate Polynomial. Journal of Symbolic Computation, 2016, 74, pp. 181-204. ⟨hal-00960896v1⟩
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