On computing polynomial GCDs in alternate bases

  • Authors:
  • Howard Cheng;George Labahn

  • Affiliations:
  • University of Lethbridge, Lethbridge, Canada;University of Waterloo, Waterloo, Canada

  • Venue:
  • Proceedings of the 2006 international symposium on Symbolic and algebraic computation
  • Year:
  • 2006

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Abstract

In this paper, we examine the problem of computing the greatest common divisor (GCD) of univariate polynomials represented in different bases. When the polynomials are represented in Newton basis or a basis of orthogonal polynomials, we show that the well-known Sylvester matrix can be generalized. We give fraction-free and modular algorithms to directly compute the GCD in the alternate basis. These algorithms are suitable for computation in domains where growth of coefficients in intermediate computations are a central concern. In the cases of Newton basis and bases using certain orthogonal polynomials, we also show that the standard subresultant algorithm can be applied easily. If the degrees of the input polynomials is at most n and the degree of the GCD is at least n/2, our algorithms outperform the corresponding algorithms using the standard power basis.