1. ON EFFICIENT NUMERICAL APPROXIMATION OF THE BILINEAR FORM c*A-1b.
- Author
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STRAKOS, ZDENĔK and TICHÝ, PETR
- Subjects
APPROXIMATION theory ,NUMERICAL analysis ,MATRICES (Mathematics) ,LINEAR systems ,ITERATIVE methods (Mathematics) ,ALGORITHMS ,MOMENTS method (Statistics) ,CONJUGATE gradient methods - Abstract
Let A ∈ ℂ
N x N be a nonsingular complex matrix and b and c be complex vectors of length N. The goal of this paper is to investigate approaches for efficient approximations of the bilinear form c*A-1 b. Equivalently, we wish to approximate the scalar value c*x, where x solves the linear system Ax = b. Here the matrix A can be very large or its elements can be too costly to compute so that A is not explicitly available and it is used only in the form of the matrix-vector product. Therefore a direct method is not an option. For A Hermitian positive definite, b*A-1 b can be efficiently approximated as a by-product of the conjugate-gradient iterations, which is mathematically equivalent to the matching moment approximations computed via the Gauss-Christoffel quadrature. In this paper we propose a new method using the biconjugate gradient iterations which is applicable to the general complex case. The proposed approach will be compared with existing ones using analytic arguments and numerical experiments. [ABSTRACT FROM AUTHOR]- Published
- 2011
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