Un algorithme d'inversion pour les matrices de Toeplitz par blocs
Un algorithme parallèle optimal pour la résolution d'un système triangulaire
Un théorème de Spitzer-Stone fort pour une matrice de Toeplitz à symbole singulier défini par une classe de fonctions analytiques
Dans cet article nous donnons une formule pour les coefficients de l’inverse des matrices de Toeplitz respectivement de symboles (cas singulier) et (cas régulier) où est une fonction appartenant à une classe de fonctions holomorphes sur un disque ouvert contenant le tore et sans zéro sur . Un cas particulier défini par où et sont des polynômes sans zéro sur est traité. Dans le cas où le symbole est singulier, cette formule présente l’intérêt d’avoir un second ordre. Dans tous les...
Uniform convergence of local multigrid methods for the time-harmonic Maxwell equation
For the efficient numerical solution of indefinite linear systems arising from curl conforming edge element approximations of the time-harmonic Maxwell equation, we consider local multigrid methods (LMM) on adaptively refined meshes. The edge element discretization is done by the lowest order edge elements of Nédélec’s first family. The LMM features local hybrid Hiptmair smoothers of Jacobi and Gauss–Seidel type which are performed only on basis functions associated with newly created edges/nodal...
Uniform convergence of local multigrid methods for the time-harmonic Maxwell equation∗
For the efficient numerical solution of indefinite linear systems arising from curl conforming edge element approximations of the time-harmonic Maxwell equation, we consider local multigrid methods (LMM) on adaptively refined meshes. The edge element discretization is done by the lowest order edge elements of Nédélec’s first family. The LMM features local hybrid Hiptmair smoothers of Jacobi and Gauss–Seidel type which are performed only on basis functions associated with newly created edges/nodal...
Unitäre Transformationen großer Matrizen.
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Updating the Singular Value Decomposition.
Use of the multigrid methods for heat radiation problem.
Using FGMRES to obtain backward stability in mixed precision.
Using least-squares to find an approximate eigenvector.
Using successive approximations for improving the convergence of GMRES method
In this paper, our attention is concentrated on the GMRES method for the solution of the system of linear algebraic equations with a nonsymmetric matrix. We perform pre-iterations before starting GMRES and put for the initial approximation in GMRES. We derive an upper estimate for the norm of the error vector in dependence on the th powers of eigenvalues of the matrix . Further we study under what eigenvalues lay-out this upper estimate is the best one. The estimate shows and numerical...
Vaidya's preconditioners: Implementation and experimental study.
Variations on Richardson's method and acceleration.
Variations on the Gram-Schmidt and the Huang algorithms for linear systems: A numerical study
In this paper we compare the numerical performance on a set of ill conditioned problems of several algorithms for linear systems based upon the explicit QR factorization and the implicit LQ factorization associated with the Huang and the modified Huang algorithms in the ABS class. The results indicate that the modified Huang algorithm is generally more accurate than the Huang algorithm and competitive with commercial codes based upon the QR factorization with Householder of Givens reflections. The...
Verallgemeinerung der Sätze von Poincaré und Perron für Systeme von Differenzengleichungen im linearen Raum
Vermeidung von Divisionen.
Wavelet compression of anisotropic integrodifferential operators on sparse tensor product spaces
For a class of anisotropic integrodifferential operators arising as semigroup generators of Markov processes, we present a sparse tensor product wavelet compression scheme for the Galerkin finite element discretization of the corresponding integrodifferential equations u = f on [0,1]n with possibly large n. Under certain conditions on , the scheme is of essentially optimal and dimension independent complexity (h-1| log h |2(n-1)) without corrupting the convergence or smoothness requirements...
Zerfallende Tridiagonalmatrizen und aneinandergesetzte Sturmsche Ketten.
Zeros of unilateral quaternionic polynomials.