Implicit iterative schemes based on singular decomposition and regularizing algorithms

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Introduction. Iterative methods of regularization play an exceptionally important role in solving a large class of ill-posed and discrete ill-conditioned problems [1-6]. They can be used to solve problems encountered in dynamics and kinetics, mathematical economics, geophysics, potential theory, antenna synthesis, acoustics, automatic processing of physical experiment results, determination of the shape of a radio pulse emitted by a source, plasma diagnostics, in ground or air geological prospecting (mathematical processing of measurements), in solving the inverse kinematic task of seismic, space research (spectroscopy), medicine Iterative regularizing algorithms are obtained from classical iterative- schemes using special stopping criteria that provide them with regularizing properties. The regularization effect in these algorithms is achieved due to matching the number of iterations with initial errors-as a regularization parameter is the number of iterations of the iterative algorithm (iterative residual principle of Tikhonov). Such a choice of the regularization parameter is easily realized, especially in iterative methods, and in most practical problems leads to results on accuracy close to optimal. Most of the practically used iterative regularizing algorithms apply explicit or implicit iterative schemes (methods) of simple iterations [1-3]. In terms of the convergence rate, implicit iterative schemes have significant advantage over explicit schemes. In this connection, implicit iterative schemes play a more important role for the methods of iterative regularization. The computational stability of implicit iterative schemes is important. This stability strongly depends on the method of solving systems of linear algebraic equations (SLAE) at each iteration. It is known that the methods of solving SLAE on the basis of singular decomposition (SVD-methods) have the largest computational stability [7, 8]. These methods allow to solve effectively even SLAE with ill-determined rank [9, 10]. A disadvantage (when solving problems large dimension) is the fact that the SVD method is poorly implemented on parallel high-performance platforms. However, in recent years some researches eliminating this lack have recently appeared [11-15]. In this paper, we propose a variant of the implicit method of simple iterations based on the use of singular decomposition (SVD-method). The speed and the numeric stability of this iteration algorithm are studied. The application of the proposed method for constructing iterative regularization algorithms is considered here. 1. Problem formulation and implicit method of simple iterations. We consider the problem of solving systems of linear equations of the form:

About the authors

Alexander I Zhdanov

Samara State Technical University

Email: zhdanovaleksan@yandex.ru
Dr. Phys. & Math. Sci., Professor; Head of Department; Dept. of Higher Mathematics & Applied Computer Science 244, Molodogvardeyskaya st., Samara, 443100, Russian Federation

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