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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Computing 21 (1979), S. 113-125 
    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Eine erweiterte Quasi-Newtonsche Gleichung wird gelöst unter Verwendung derW-V verallgemeinerten Inverse und ergibt eine einheitliche Ableitung der bekannten Quasi-Newtonschen Methode für die Lösung von nichtlinearen algebraischen Gleichungssystemen. Dieser Zugang ermöglicht es uns, neue Formeln für dünnbesetzte und nicht dünnbesetzte Systeme zu erhalten und auch zu bestimmen, welche Normen der Update-Matrizen bei verschiedenen brauchbaren Quasi-Newtonschen Update-Formeln minimisiert werden.
    Notes: Abstract An augmented quasi-Newton equation is solved by using theW-V generalized inverse to give a unified derivation of the known quasi-Newton methods for solving systems of nonlinear algebraic equations. This approach makes it possible to get new formulas for sparse and non-sparse systems, and also to determine what norms of the update matrices are minimized when several useful quasi-Newton update formulas are derived.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computing 3 (1968), S. 268-279 
    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir betrachten das folgende Problem: Wie soll die optimale Ordnung der Spalten einer gegebenen sparse Matrize orthonormalisiert werden, so daß die sich ergebende Matrize so sparse wie möglich ist. Es wird gezeigt wie unter gewissen Bedingungen das Optimum bestimmt werden kann. Verschiedene Methoden sind gegeben, welche vom Berechnungsstandpunkt aus einfach sind, und welche eine ziemlich genaue Annäherung an die optimale Spaltenordnung geben. Die Resultate der Berechnungsexperimente, die mit zufällig erzeugten Matrizen durchgeführt wurden, sind auch angegeben. Die Analyse und die Resultate dieser Arbeit gelten für dieGram-Schmidt und auch für dieHouseholdersche Orthonormalisierungsmethode.
    Notes: Summary The problem of finding the optimum order in which the columns of a given sparse matrix should be orthonormalized, such that the resulting matrix is as sparse as possible, is discussed. It is shown how, under certain conditions, the optimum can be determined. Some computationally simple methods, which give a reasonably close approximation to the optimum column order, are given. The results of computational experiments performed on randomly generated matrices are also given. The analysis and the results of the paper hold for both theGram-Schmidt and theHouseholder methods of orthonormalization.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Computing 7 (1971), S. 236-239 
    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es werden zwei Methoden zur Berechnung der generalisiertenMoore-Penrose-Inversen und explizite Ausdrücke für die generalisierten Inversen (1, 2, 3) und (1, 2, 4) einer Matrix gebracht.
    Notes: Summary Two methods for computing theMoore-Penrose generalized inverse and explicit expressions for the (1, 2, 3) and the (1, 2, 4) generalized inverses of a matrix are given.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Computing 33 (1984), S. 315-329 
    ISSN: 1436-5057
    Keywords: 65K ; Unconstrained minimization ; quasi-Newton method ; LDR factorization of matrix ; sparse matrix techniques ; updating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Eine neue Quasi-newton-Methode für gewisse Minimalisierungsprobleme ohne Nebenbedingungen ist angegeben. Sie benutzt dünnbesetzte Tripelfaktorisierungen einer Approximation der Hesseschen Matrix. Bei jedem Schritt wird eine neue Spalte und eine entsprechende Zeile in der Approximation der Hesseschen Matrix bestimmt und ihre Faktorisierung wird umgeformt. Unsere Methode behandelt das gleiche Problem wie die Methode von Bräuninger in [2]. Wir verwenden jedoch ein Scheme von Rang zwei statt von Rang eins. Unsere Methode spart über die Hälfte der von Bräuninger benötigten Rechenoperationen ein. Überdies nutzt unsere Methode das Auftreten vieler Nullen aus, und es brauchen deshalb nur die von Null verschiedenen Stellen der Faktoren gespeichert zu werden. Durch geeignete Maßnahmen läßt sich leicht sicherstellen, daß die Approximationen positiv definitiv ausfallen. Unter gewöhnlichen Bedingungen konvergiert unsere Methode global während sie lokal superlinear in den geraden Schritten mit Ordnung ρ konvergiert.
    Notes: Abstract A new quasi-Newton method for unconstrained minimization is presented. It uses sparse triple factorization of an approximation to the sparse Hessian matrix. At each step a new column and a corresponding row of the approximation to the Hessian is determined and its triple factorization is updated. Our method deals with the same updating problem as in J. Bräuninger's paper [2]. However, we make use of a rank-two instead of a rank-one updating scheme. Our method saves over half the number of operations required in J. Bräuninger's method. Moreover, our method utilizes the sparsity and, therefore, only the nonzero entries of the factors need to be stored. The positive definiteness can be preserved easily by taking suitable precautions. Under reasonable conditions our method is globally convergent and locally superlinearly evenn-step ρ-order convergent.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Computing 9 (1972), S. 1-7 
    ISSN: 1436-5057
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird die Berechnung einer dünn besetzten faktorisirten Form für die Inverse einer dünn besetzten Matrix beschrieben. Die Matrix wird zunächst durch Permutationen in eine obere Dreiecks-Block-matrix überführt, sodann wird eine Variante der bekannten Gauß-Elimination angewandt. Neue von Null verschiedene Elemente können nur in den Diagonalblocks entstehen; für diese Diagonal-blocks lassen sich Methoden zur Beschränkung der Entstehung neuer von Null verschiedener Elemente leicht anwenden, da ihre Dimension i. a. klein gegenüber der Dimension der gesamten Matrix ist.
    Notes: Summary The computation of a sparse factored form of inverse of a given sparse matrix is described. The given matrix is first permuted to a block upper triangular form by row-column permutations, then a simple variation of the well-known Gaussian elimination method is utilized to get the inverse. The growth of non-zero elements during the computation is limited to the diagonal blocks. Techniques for minimizing the growth of non-zero elements in the diagonal blocks are easy to use, as the blocks turn out to be generally much smaller than the whole matrix.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    BIT 20 (1980), S. 223-232 
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Cubic splines on splines and quintic spline interpolations are used to approximate the derivative terms in a highly accurate scheme for the numerical solution of two-point boundary value problems. The storage requirement is essentially the same as for the usual trapezoidal rule but the local accuracy is improved fromO(h 3) to eitherO(h 6) orO(h 7), whereh is the net size. The use of splines leads to solutions that reflect the smoothness of the slopes of the differential equations.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is shown that by introducing one or three interpolated values in each subinterval the local truncation error of finite difference (box, gap and deferred correction) methods can be decreased by two to four orders of magnitude when solving two point boundary value ordinary differential equations.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Various interpolation-based schemes are used to construct a variable order algorithm with local error control for the numerical solution of two-point boundary value problems. Results of computational experiments are presented to demonstrate the empirical relationship between prescribed local error and the resultant global error in the computed solution.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A method is described for handling systems of linear equations with a sparse coefficient matrix as economically as possible. In particular, a convenient rule for the order of pivoting is given. Numerical experiments indicating considerable savings have also been performed.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    BIT 8 (1968), S. 232-242 
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new formulation of the ascent algorithm for the Chebyshev solution of linear systems is given. This leads to two algorithms, which are similar to the ordinary simplex and the product form of inverse algorithms for the solution of linear programming problems.
    Type of Medium: Electronic Resource
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