Improved Budan-Fourier Count for Root Finding - Inria - Institut national de recherche en sciences et technologies du numérique
Pré-Publication, Document De Travail Année : 2011

Improved Budan-Fourier Count for Root Finding

Résumé

Given a degree n univariate polynomial f(x), the Budan-Fourier function Vf (x) counts the sign changes in the sequence of derivatives of f evaluated at x. The values at which this function jumps are called the virtual roots of f, these include the real roots of f and any multiple root of its derivatives. This concept was introduced (by an equivalent property) by Gonzales-Vega, Lombardi, Mahe and then studied by Coste, Lajous, Lombardi, Roy .The set of virtual roots provide a good real substitute to the set of complex roots; it depends continuously on the coefficients of f. We will describe a root isolation method by a subdivision process based on a generalized Budan-Fourier count, fast evaluation and Newton like approximations. Our algorithm will provide isolating intervals for all augmented virtual roots of f. For a polynomials with integer coefficients of length size = ~O(n), its bit cost is in ~O (n5). We rely on a new connexity property of the Budan table of f which collects the signs of the iterated derivatives of f.
On decrit un nouvel algorithme d'isolation des racines d'un polynome f a l'aide du compte de changements de signes de Budan Fourier. On utilise une nouvelle propriete de connexite dans le tableau de variation de f.
Fichier principal
Vignette du fichier
RootFindingGalligo.pdf (245.31 Ko) Télécharger le fichier
Origine Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

hal-00653762 , version 1 (20-12-2011)

Identifiants

  • HAL Id : hal-00653762 , version 1

Citer

André Galligo. Improved Budan-Fourier Count for Root Finding. 2011. ⟨hal-00653762⟩
135 Consultations
719 Téléchargements

Partager

More