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Please use this identifier to cite or link to this item: http://hdl.handle.net/10277/762

Authors: Durastante, Fabio
Internal Tutor: SERRA CAPIZZANO, STEFANO
Tutor: BERTACCINI, DANIELE
Title: Preconditioned fast solvers for large linear systems with specific sparse and/or Toeplitz-like structures and applications
Abstract: In this thesis, the design of the preconditioners we propose starts from applications instead of treating the problem in a completely general way. The reason is that not all types of linear systems can be addressed with the same tools. In this sense, the techniques for designing efficient iterative solvers depends mostly on properties inherited from the continuous problem, that has originated the discretized sequence of matrices. Classical examples are locality, isotropy in the PDE context, whose discrete counterparts are sparsity and matrices constant along the diagonals, respectively. Therefore, it is often important to take into account the properties of the originating continuous model for obtaining better performances and for providing an accurate convergence analysis. We consider linear systems that arise in the solution of both linear and nonlinear partial differential equation of both integer and fractional type. For the latter case, an introduction to both the theory and the numerical treatment is given. All the algorithms and the strategies presented in this thesis are developed having in mind their parallel implementation. In particular, we consider the processor-co-processor framework, in which the main part of the computation is performed on a Graphics Processing Unit (GPU) accelerator. In Part I we introduce our proposal for sparse approximate inverse preconditioners for either the solution of time-dependent Partial Differential Equations (PDEs), Chapter 3, and Fractional Differential Equations (FDEs), containing both classical and fractional terms, Chapter 5. More precisely, we propose a new technique for updating preconditioners for dealing with sequences of linear systems for PDEs and FDEs, that can be used also to compute matrix functions of large matrices via quadrature formula in Chapter 4 and for optimal control of FDEs in Chapter 6. At last, in Part II, we consider structured preconditioners for quasi-Toeplitz systems. The focus is towards the numerical treatment of discretized convection-diffusion equations in Chapter 7 and on the solution of FDEs with linear multistep formula in boundary value form in Chapter 8.
Keywords: Iterative solvers, spase matrices, Toeplitz matrices, spectral analysis
Subject MIUR : MAT/08 ANALISI NUMERICA
Issue Date: 2017
Language: eng
Doctoral course: Informatica e matematica del calcolo
Academic cycle: 30
Publisher: Università degli Studi dell'Insubria
Citation: Durastante, F.Preconditioned fast solvers for large linear systems with specific sparse and/or Toeplitz-like structures and applications (Doctoral Thesis, Università degli Studi dell'Insubria, 2017).

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