Segnalo 2 seminari che il Prof. Jacek Gondzio (School of Mathematics, University of Edinburgh) terrà nel corso della sua visita presso il Dipartimento di Ingegneria Industriale (UNIFI) e il Dipartimento di Matematica (UNIBO).

********************************* Ven 13 Marzo, ore 11:00 Luogo: BOLOGNA aula: Seminario I, Dipartimento di Matematica, Università di Bologna

TITOLO: "Preconditioners for higher order methods in signal reconstruction"

ABSTRACT:

We address efficient preconditioning techniques for the inexact second-order methods applied to solve various sparse approximation problems arising in signal/image reconstruction. The preconditioners exploit two features of such problems: (i) sparsity of the solution, and (ii) near-orthogonality of the matrices involved. The latter originates from the restricted isometry properties frequently assumed in such applications. Spectral analysis of the preconditioners and their practical efficiency when solving linear systems in the Newton Conjugate Gradient method will be presented. If time permits then a few comments on the some other problems originating from the "Big Data" buzz will also be given.

J. Gondzio joint work with I. Dassios, K. Fountoulakis and P. Zhlobich

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Ven 20 Marzo, ore 14:00 Luogo: FIRENZE aula: Aula Tricerri, Dipartimento di Matematica e Informatica 'Ulisse Dini' Università di Firenze

TITOLO: "Preconditioners for higher order methods in big data optimization"

ABSTRACT:

We address efficient preconditioning techniques for the second-order methods applied to solve various sparse approximation problems arising in big data optimization. The preconditioners cleverly exploit special features of such problems and cluster the spectrum of eigenvalues around one. The inexact Newton Conjugate Gradient method excels in these conditions. Numerical results of solving L1-regularization problems of unprecedented sizes will be presented.

J. Gondzio joint work K. Fountoulakis

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Cordiali saluti,

Margherita Porcelli

-- Margherita Porcelli Dipartimento di Matematica Università di Bologna Piazza di Porta S. Donato, 5 40127 - Bologna - Italy phone : +39-051-2094423 home page: http://web.math.unifi.it/users/porcelli