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Remarks on polynomial methods for solving systems of linear algebraic equations

Krzysztof Moszyński (1992)

Applications of Mathematics

For a large system of linear algebraic equations A x = b , the approximate solution x k is computed as the k -th order Fourier development of the function 1 / z , related to orthogonal polynomials in L 2 ( Ω ) space. The domain Ω in the complex plane is assumed to be known. This domain contains the spectrum σ ( A ) of the matrix A . Two algorithms for x k are discussed. Two possibilities of preconditioning by an application of the so called Richardson iteration process with a constant relaxation coefficient are proposed. The case...

Replicant compression coding in Besov spaces

Gérard Kerkyacharian, Dominique Picard (2010)

ESAIM: Probability and Statistics

We present here a new proof of the theorem of Birman and Solomyak on the metric entropy of the unit ball of a Besov space B π , q s on a regular domain of ℝ d . The result is: if s - d(1/π - 1/p)+> 0, then the Kolmogorov metric entropy satisfies H(ε) ~ ε-d/s. This proof takes advantage of the representation of such spaces on wavelet type bases and extends the result to more general spaces. The lower bound is a consequence of very simple probabilistic exponential inequalities. To prove the upper bound,...

Replicant compression coding in Besov spaces

Gérard Kerkyacharian, Dominique Picard (2003)

ESAIM: Probability and Statistics

We present here a new proof of the theorem of Birman and Solomyak on the metric entropy of the unit ball of a Besov space B π , q s on a regular domain of ℝ d . The result is: if s - d ( 1 / π - 1 / p ) + > 0 , then the Kolmogorov metric entropy satisfies H ( ϵ ) ∼ ϵ - d / s . This...

Residual norm behavior for Hybrid LSQR regularization

Havelková, Eva, Hnětynková, Iveta (2023)

Programs and Algorithms of Numerical Mathematics

Hybrid LSQR represents a powerful method for regularization of large-scale discrete inverse problems, where ill-conditioning of the model matrix and ill-posedness of the problem make the solutions seriously sensitive to the unknown noise in the data. Hybrid LSQR combines the iterative Golub-Kahan bidiagonalization with the Tikhonov regularization of the projected problem. While the behavior of the residual norm for the pure LSQR is well understood and can be used to construct a stopping criterion,...

Resilient asynchronous primal Schur method

Guillaume Gbikpi-Benissan, Frédéric Magoulès (2022)

Applications of Mathematics

This paper introduces the application of asynchronous iterations theory within the framework of the primal Schur domain decomposition method. A suitable relaxation scheme is designed, whose asynchronous convergence is established under classical spectral radius conditions. For the usual case where local Schur complement matrices are not constructed, suitable splittings based only on explicitly generated matrices are provided. Numerical experiments are conducted on a supercomputer for both Poisson's...

Robust domain decomposition preconditioners for abstract symmetric positive definite bilinear forms

Yalchin Efendiev, Juan Galvis, Raytcho Lazarov, Joerg Willems (2012)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

An abstract framework for constructing stable decompositions of the spaces corresponding to general symmetric positive definite problems into “local” subspaces and a global “coarse” space is developed. Particular applications of this abstract framework include practically important problems in porous media applications such as: the scalar elliptic (pressure) equation and the stream function formulation of its mixed form, Stokes’ and Brinkman’s equations. The constant in the corresponding abstract...

Robust domain decomposition preconditioners for abstract symmetric positive definite bilinear forms

Yalchin Efendiev, Juan Galvis, Raytcho Lazarov, Joerg Willems (2012)

ESAIM: Mathematical Modelling and Numerical Analysis

An abstract framework for constructing stable decompositions of the spaces corresponding to general symmetric positive definite problems into “local” subspaces and a global “coarse” space is developed. Particular applications of this abstract framework include practically important problems in porous media applications such as: the scalar elliptic (pressure) equation and the stream function formulation of its mixed form, Stokes’ and Brinkman’s equations....

Robust operator estimates and the application to substructuring methods for first-order systems

Christian Wieners, Barbara Wohlmuth (2014)

ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique

We discuss a family of discontinuous Petrov–Galerkin (DPG) schemes for quite general partial differential operators. The starting point of our analysis is the DPG method introduced by [Demkowicz et al., SIAM J. Numer. Anal. 49 (2011) 1788–1809; Zitelli et al., J. Comput. Phys. 230 (2011) 2406–2432]. This discretization results in a sparse positive definite linear algebraic system which can be obtained from a saddle point problem by an element-wise Schur complement reduction applied to the test space....

Robust preconditioners for the matrix free truncated Newton method

Lukšan, Ladislav, Matonoha, Ctirad, Vlček, Jan (2010)

Programs and Algorithms of Numerical Mathematics

New positive definite preconditioners for the matrix free truncated Newton method are given. Corresponding algorithms are described in detail. Results of numerical experiments that confirm the efficiency and robustness of the preconditioned truncated Newton method are reported.

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