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D.7.8 rootsur_lib

Library:
rootsur.lib
Purpose:
Counting number of real roots of univariate polynomial
Author:
Enrique A. Tobis, etobis@dc.uba.ar

Overview:
Routines for bounding and counting the number of real roots of a univariate polynomial, by means of several different methods, namely Descartes' rule of signs, the Budan-Fourier theorem, Sturm sequences and Sturm-Habicht sequences. The first two give bounds on the number of roots. The other two compute the actual number of roots of the polynomial. There are several wrapper functions, to simplify the application of the aforesaid theorems and some functions to determine whether a given polynomial is univariate. References: Basu, Pollack, Roy, "Algorithms in Real Algebraic Geometry", Springer, 2003.

Procedures:

D.7.8.1 isuni  Checks whether a polynomials is univariate
D.7.8.2 whichvariable  The only variable of a univariate monomial (or 0)
D.7.8.3 varsigns  Number of sign changes in a list
D.7.8.4 boundBuFou  Bound for number of real roots of poly p in interval (a,b)
D.7.8.5 boundposDes  Bound for the number of positive real roots of poly p
D.7.8.6 boundDes  Bound for the number of real roots of poly p
D.7.8.7 allrealst  Checks whether all the roots of a poly are real (via Sturm)
D.7.8.8 maxabs  A bound for the maximum absolute value of a root of a poly
D.7.8.9 allreal  Checks whether all the roots of a poly are real (via St-Ha)
D.7.8.10 sturm  Number of real roots of a poly on an interval (via Sturm)
D.7.8.11 sturmseq  Sturm sequence of a polynomial
D.7.8.12 sturmha  Number of real roots of a poly in (a,b) (via Sturm-Habicht)
D.7.8.13 sturmhaseq  A Sturm-Habicht Sequence of a polynomial
D.7.8.14 reverse  Reverses a list
D.7.8.15 nrroots  The number of real roots of p
D.7.8.16 isparam  Returns 0 iff the polynomial has non-parametric coefficients


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