18 research outputs found
Computing Nearest Gcd with Certification
International audienceA bisection method, based on exclusion and inclusion tests, is used to address the nearest univariate gcd problem formulated as a bivariate real minimization problem of a rational fraction. The paper presents an algorithm, a first implementation and a complexity analysis relying on Smale's -theory. We report its behavior on an illustrative example
Minimizing Rational Functions by Exact Jacobian SDP Relaxation Applicable to Finite Singularities
This paper considers the optimization problem of minimizing a rational
function. We reformulate this problem as polynomial optimization by the
technique of homogenization. These two problems are shown to be equivalent
under some generic conditions. The exact Jacobian SDP relaxation method
proposed by Nie is used to solve the resulting polynomial optimization. We also
prove that the assumption of nonsingularity in Nie's method can be weakened as
the finiteness of singularities. Some numerical examples are given to
illustrate the efficiency of our method.Comment: 23 page
Over-constrained Weierstrass iteration and the nearest consistent system
We propose a generalization of the Weierstrass iteration for over-constrained
systems of equations and we prove that the proposed method is the Gauss-Newton
iteration to find the nearest system which has at least common roots and
which is obtained via a perturbation of prescribed structure. In the univariate
case we show the connection of our method to the optimization problem
formulated by Karmarkar and Lakshman for the nearest GCD. In the multivariate
case we generalize the expressions of Karmarkar and Lakshman, and give
explicitly several iteration functions to compute the optimum.
The arithmetic complexity of the iterations is detailed
GPGCD: An iterative method for calculating approximate GCD of univariate polynomials
We present an iterative algorithm for calculating approximate greatest common
divisor (GCD) of univariate polynomials with the real or the complex
coefficients. For a given pair of polynomials and a degree, our algorithm finds
a pair of polynomials which has a GCD of the given degree and whose
coefficients are perturbed from those in the original inputs, making the
perturbations as small as possible, along with the GCD. The problem of
approximate GCD is transfered to a constrained minimization problem, then
solved with the so-called modified Newton method, which is a generalization of
the gradient-projection method, by searching the solution iteratively. We
demonstrate that, in some test cases, our algorithm calculates approximate GCD
with perturbations as small as those calculated by a method based on the
structured total least norm (STLN) method and the UVGCD method, while our
method runs significantly faster than theirs by approximately up to 30 or 10
times, respectively, compared with their implementation. We also show that our
algorithm properly handles some ill-conditioned polynomials which have a GCD
with small or large leading coefficient.Comment: Preliminary versions have been presented as
doi:10.1145/1576702.1576750 and arXiv:1007.183
Computing Nearest Gcd with Certification
International audienceA bisection method, based on exclusion and inclusion tests, is used to address the nearest univariate gcd problem formulated as a bivariate real minimization problem of a rational fraction. The paper presents an algorithm, a first implementation and a complexity analysis relying on Smale's -theory. We report its behavior on an illustrative example