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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Computing 37 (1986), S. 315-334 
    ISSN: 1436-5057
    Keywords: 65L05 ; 65L10 ; Two-point boundary value problems ; Runge-Kutta methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die standardmäßige Verwendung von impliziten RK-Verfahren zur Lösung von 2-Punkt Randwertproblemen erfordert für die Berechnung der Stufen die Lösung eines Systems vonn×s nichtlinearen Gleichungen, won die Anzahl der Differentialgleichungen unds die Stufenanzahl des impliziten RK-Verfahrens ist. Man kann jedoch für 2-Punkt Randwertprobleme eine Teilmenge der IRK-Verfahren auswählen, für die die Lösung von Gleichungssystemen nicht nötig ist; die Stufen können, wie bei expliziten RK-Verfahren, direkt berechnet werden. Trotzdem haben diese Verfahren bessere Stabilitätseigenschaften als explizite RK-Verfahren. Wir nennen diese neuen Formeln 2-Punkt explizite RK (TPERK)-Verfahren. Weil ihre Stufen explizit berechnet werden können, kann mit ihnen die Lösung eines 2-Punkt-Randwertproblems effizienter als mit einem impliziten RK-Verfahren berechnet werden. Wir beschreiben auch eine Unterklasse von symmetrischen TPERK-Verfahren, die ATPERK-Verfahren, die eine Reihe nützlicher Eigenschaften aufweisen.
    Notes: Abstract The standard approach to applying IRK methods in the solution of two-point boundary value problems involves the solution of a non-linear system ofn×s equations in order to calculate the stages of the method, wheren is the number of differential equations ands is the number of stages of the implicit Runge-Kutta method. For two-point boundary value problems, we can select a subset of the implicit Runge-Kutta methods that do not require us to solve a non-linear system; the calculation of the stages can be done explicitly, as is the case for explicit Runge-Kutta methods. However, these methods have better stability properties than the explicit Runge-Kutta methods. We have called these new formulas two-point explicit Runge-Kutta (TPERK) methods. Their most important property is that, because their stages can be computed explicity, the solution of a two-point boundary value problem can be computed more efficiently than is possible using an implicit Runge-Kutta method. We have also developed a symmetric subclass of the TPERK methods, called ATPERK methods, which exhibit a number of useful properties.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computing 55 (1995), S. 223-236 
    ISSN: 1436-5057
    Keywords: 65L05 ; 65L06 ; Runge-Kutta methods ; interpolations ; delay differential equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Beim numerischen Lösen von Differentialgleichungen mit nacheilendem Argument (DDEs) mit Hilfe von stetigen expliziten Runge-Kutta Methoden entstehen Schwierigkeiten, wenn die Argumentverzögerung verschwindet oder zumindest kleiner als die Verfahrensschrittweite wird. In dieser Situation wird der herkömmlich explizite und sequentielle Prozeß der Stufenberechnungen des RK-Schemas ein impliziter und muß überdies iteriert werden. In dieser Arbeit werden einige Iterationsmethoden untersucht und deren Ordnung bestimmt.
    Notes: Abstract In the numerical solution of delay differential equations by a continuous explicit Runge-Kutta method a difficulty arises when the delay vanishes or becomes smaller than the stepsize the method would like to use. In this situation the standard explicit sequential process of computing the Runge-Kutta stages becomes an implicit process and an iteration scheme must be adopted. We will consider alternative iteration schemes and investigate their order.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Computing 42 (1989), S. 341-352 
    ISSN: 1436-5057
    Keywords: 65L05 ; Initial-value problems ; error control ; tolerance proportionality ; local extrapolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Toleranztreue wird als minimale Bedingung dafür erkannt, daß eine einheitliche Interpretation der vom Benutzer geforderten Genauigkeit bei der Lösung von Anfangswertaufgaben möglich ist. Es werden Ergebnisse angeführt, die zeigen, daß ein Code den lokalen Fehler pro Einheitsschritt kontrollieren muß, um Toleranztreue zu erreichen. In Mehrschritt-Codes kann dieser Effekt dadurch erreicht werden, daß ein Korrektor-Verfahren verwendet wird, das eine Ordnung genauer ist als das Prädiktor-Verfahren. Diese Strategie ist leicht anzuwenden und führt zu besserer Toleranztreue als die Strategie des lokalen Fehlers pro Schritt, die oft bei Software für steife Probleme verwendet wird. Numerische Ergebnisse wurden mit zwei Codes gewonnen, die auf die vorgeschlagene Strategie modifiziert wurden. Die Ergebnissezeigen, daß durch die Modifikation eine signifikante Verbesserung der Toleranztreue bei geringem zusätzlichen Aufwand erreicht werden kann.
    Notes: Abstract Tolerance proportionality is identified as a minimum requirement for a more uniform interpretation of the user's requested accuracy in software for the solution of initial-value problems. Results are quoted that show that a code must control the local error per unit step in order to achieve tolerance proportionality. This effect can be obtained in codes based on multistep formulas by using a corrector formula of one order higher than the predictor formula. This strategy is simple to implement and leads to better tolerance proportionality than the local error per step strategy often used in stiff software.Numerical results are obtained from two existing solvers that have been modified to use the proposed strategy. These results show that there is a significant improvement in tolerance proportionality in the modified codes at little extra cost over the original versions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    BIT 15 (1975), S. 10-48 
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper describes a technique for comparing numerical methods that have been designed to solve stiff systems of ordinary differential equations. The basis of a fair comparison is discussed in detail. Measurements of cost and reliability are made over a collection of 25 carefully selected problems. The problems have been designed to show how certain major factors affect the performance of a method. The technique is applied to five methods, of which three turn out to be quite good, including one based on backward differentiation formulas, another on second derivative formulas, and a third on extrapolation. However, each of the three has a weakness of its own, which can be identified with particular problem characteristics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    BIT 18 (1978), S. 276-281 
    ISSN: 1572-9125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Algorithms for solving matrix pencil systems of linear equations, of the form (A+γB)x=c+γd, are developed and analysed. The techniques that are discussed are based on methods for the generalized eigenvalue problem and avoid refactoring a matrix when the scalar γ changes. Numerical results are presented which demonstrate the advantages of the new techniques.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    BIT 27 (1987), S. 403-423 
    ISSN: 1572-9125
    Keywords: 65L05 ; 65L20 ; 34A50 ; Runge-Kutta methods ; reflected methods ; symmetric methods ; efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper we apply the theory for implicit Runge-Kutta methods presented by Stetter to a number of subclasses of methods that have recently been discussed in the literature. We first show how each of these classes can be expressed within this theoretical framework and from this we are able to establish a number of relationships among these classes. In addition to improving the current state of understanding of these methods, their expression within this theoretical framework makes it possible for us to obtain results giving general forms for their stability functions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    BIT 31 (1991), S. 647-663 
    ISSN: 1572-9125
    Keywords: 65L05 ; Runge-Kutta ; parallelism ; defect ; interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract How can small-scale parallelism best be exploited in the solution of nonstiff initial value problems? It is generally accepted that only modest gains inefficiency are possible, and it is often the case that “fast” parallel algorithms have quite crude error control and stepsize selection components. In this paper we consider the possibility of using parallelism to improvereliability andfunctionality rather than efficiency. We present an algorithm that can be used with any explicit Runge-Kutta formula. The basic idea is to take several smaller substeps in parallel with the main step. The substeps provide an interpolation facility that is essentially free, and the error control strategy can then be based on a defect (residual) sample. If the number of processors exceeds (p − 1)/2, wherep is the order of the Runge-Kutta formula, then the interpolant and the error control scheme satisfy very strong reliability conditions. Further, for a given orderp, the asymptotically optimal values for the substep lengths are independent of the problem and formula and hence can be computed a priori. Theoretical comparisons between the parallel algorithm and optimal sequential algorithms at various orders are given. We also report on numerical tests of the reliability and efficiency of the new algorithm, and give some parallel timing statistics from a 4-processor machine.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 16 (1980), S. 13-18 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Fixed stepsize low-order methods are the most widely used technique for solving the second-order initial value problems that arise in structural dynamics. In this paper we shall describe the special stability difficulty that arises with this class of problem and we will outline how variable stepsize techniques can cope with this difficulty and result in efficient numerical methods.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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