Approximately singular systems and ill-conditioned polynomial systems

  • Authors:
  • Tateaki Sasaki;Daiju Inaba

  • Affiliations:
  • University of Tsukuba, Tsukuba-city, Ibaraki, Japan;Japanese Association of Mathematics Certification, Tokyo, Japan

  • Venue:
  • CASC'12 Proceedings of the 14th international conference on Computer Algebra in Scientific Computing
  • Year:
  • 2012

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Abstract

By "approximately singular system" we mean a system of multivariate polynomials the dimension of whose variety is increased by small amounts of perturbations. First, we give a necessary condition that the given system is approximately singular. Then, we classify polynomial systems which seems ill-conditioned to solve numerically into four types. Among these, the third one is approximately singular type. We give a simple well-conditioning method for the third type. We test the third type and its well-conditioned systems by various examples, from viewpoints of "global convergence", "local convergence" and detail of individual computation. The results of experiments show that our well-conditioning method improves the global convergence largely.