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Avviso di Seminario
by Dario A. Bini 11 Jul '17

11 Jul '17

Avviso di Seminario: Speaker: Rajendra Bhatia Affiliation: Indian Statistical Institute, Delhi Date: July 11 Time: 11:00 -- 12:00 Place: Aula Magna Title: The Bures-Wasserstein distance on positive definite matrices Abstract: We will discuss an interesting metric on the space of positive definite matrices, called the Bures distance in the quantum information literature and the Wasserstein metric in optimal transport. This has connections with Riemannian geometry, statistics, QIT and optimal transport. We will explain these connections. The two-variable and several-variable mean with respect to this metric will be described. Our perspective from matrix analysis leads to simpler proofs and suggests new problems.

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Seminari Benzi e Qi
by Federico Poloni 05 Jun '17

05 Jun '17

Buongiorno, segnalo questo seminario di Michele Benzi in SNS, e ne approfitto per ricordare anche quello di Liqun Qi di lunedì prossimo: > Speaker: Liqun Qi, The Hong Kong Polytechnic University, Department of > Applied Mathematics > > Title: Tensor Analysis: Spectral Theory and Special Tensors > > Room: Sala Riunioni, Dipartimento di Matematica > > Time: Monday, June 12, 11:00 -------- Forwarded Message -------- Subject: [Settimanale] avviso Seminario di Matematica prof. Michele Benzi (8.06.2017) Date: Mon, 5 Jun 2017 10:13:39 +0200 From: Valeria Giuliani <valeria.giuliani(a)sns.it> SEMINARIO DI MATEMATICA Giovedì 8 giugno 2017 ore 11:00 _Scuola Normale Superiore_ Pisa Aula Marie Curie *_ _* * **Michele Benzi*** /(Samuel Candler Dobbs Professor - Emory University)/ */ /* terrà un seminario dal titolo: *“**Decay properties of matrix functions with applications to electronic structure computations**”*** * * *Abstract:* /Functions of matrices, such as the matrix exponential or the square root, arise in a number of scientific and technical applications, ranging from quantum mechanical computations to the structural analysis of complex graphs and networks. The actual numerical evaluation of functions of large and sparse matrices can be quite challenging, and much effort has been devoted to this problem in recent years. An important property that is frequently exhibited by analytic functions of large and sparse matrices is the rapid off-diagonal decay of the matrix entries; careful exploitation of this property can lead to algorithms with optimal computational complexity (this means that the cost scales linearly with the dimension of the problem)./// /In this talk I will present some rigorous estimates on the size of the off-diagonal entries of analytic matrix functions. As a special case, the theory yields a proof of the exponential decay, or "localization", of the density matrix (spectral projector) arising in electronic structure computations for gapped systems, a classical problem in solid state physics and quantum chemistry. In addition to giving a precise mathematical form to W. Kohn's notion of "nearsightedness of electronic matter", these estimates provide a sound basis for the development of linear scaling methods./*//* */ /* Tutti gli interessati sono invitati a partecipare. Classe di Scienze Matematiche e Naturali Valeria Giuliani Scuola Normale Superiore Servizio alla Didattica e Allievi tel. 050 509260 Piazza dei Cavalieri, 7 56126 Pisa E-mail: valeria.giuliani(a)sns.it <mailto:valeria.giuliani@sns.it> E-mail: classi(a)sns.it <mailto:classi@sns.it>

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Fwd: ONE DAY ON NUMERICAL LINEAR ALGEBRA
by Federico Poloni 24 May '17

24 May '17

Ricevo da Dario Bini e inoltro. --- ONE DAY ON NUMERICAL LINEAR ALGEBRA June 14, 2017, Room 2AB40 - Dipartimento di Matematica "Tullio Levi-Civita", Universita' di Padova -Torre Archimede, Via Trieste 63, Padova Nel mese di giugno il Dipartimento di Matematica ospitera' tre reputati ricercatori internazionali nell'ambito dell'Algebra Lineare Numerica, di cui due vincitori delle selezioni Visiting Professor Cariparo 2016 e Visiting Scientist dell'Università di Padova. Si è dunque pensato di raccogliere i loro tre seminari in una giornata dedicata a tali tematiche. I seminari sono: 9:30-10:30 Gérard MEURANT (Paris, France) An optimal Q-OR method for solving nonsymmetric linear systems 11:00-12:00 Claude BREZINSKI (Univ. of Lille, France) Shanks sequence transformations and Anderson acceleration 14:30-15:30 Lothar REICHEL (Kent State University, USA) Generalized Krylov subspace methods for lp-lq minimization with application to image restoration Nella locandina allegata si puo' prendere visione degli abstracts e delle tempistiche di svolgimento dell'evento. La giornata si concludera' con una sessione di commenti e di discussione tra i partecipanti e gli speakers. Potranno pertanto essere sottoposti problemi particolari e richieste di approfondimenti. Tutti gli interessati sono invitati a partecipare. Non è prevista una registrazione, ma per ragioni logistiche, seppure non obbligatoria, sara' utile una potenziale manifestazione di partecipazione inviando una mail a michela(a)math.unipd.it Gli organizzatori M. Redivo-Zaglia, F. Tudisco

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Numerical analysis seminar: L.Q. Qi
by Federico Poloni 11 May '17

11 May '17

Speaker: Liqun Qi, The Hong Kong Polytechnic University, Department of Applied Mathematics Title: Tensor Analysis: Spectral Theory and Special Tensors Room: Sala Riunioni, Dipartimento di Matematica Time: Monday, June 12, 11:00 Abstract: Eigenvalues for tensors were introduced in 2005. Since then, a rich theory on eigenvalues of tensors and special tensors has been developed. There are two main definitions of eigenvalues of tensors. One definition is based upon homogeneous polynomial systems. This definition extends the definition of eigenvalues of matrices. A complex number is an eigenvalue of a ``square'' tensor if and only if it is a root of the characteristic polynomial of that tensor. The sum of all the eigenvalues of that tensor is equal to the sum of the diagonal entries of that tensor, while the product of all the eigenvalues of that tensor is equal to the determinant of that tensor. An eigenvalue of a real tensor with a real eigenvector is called an H-eigenvalue. An even order real symmetric tensor is positive semi-definite if and only if all of its H-eigenvalues are nonnegative. Various tensor eigenvalue inclusion theorems have been developed. Another tensor eigenvalue definition has the merit that the eigenvalues under this definition are invariant under orthonormal transformations. This makes eigenvalues under this definition found their applications in engineering, physics and mechanics. Based upon the tensor eigenvalue theory, theories on special tensors have also been developed. In particular, the Perron-Frobenius theory for irreducible nonnegative tensors and weakly irreducible nonnegative tensors has been developed, and found applications in spectral hypergraph theory and higher order Markov chains. Other special tensors include positive semi-definite tensors, sum-of-squares tensors, completely positive tensors and copositive tensors, etc. Eigenvalues of tensors also found their applications in magnetic resonance imaging, elastic mechanics, liquid crystal study, quantum entanglement and classicality problems, etc. A book “Tensor Analysis: Spectral Theory and Special Tensors'' is published by SIAM in April this year. ==== Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Numerical Analysis Seminar: R. Vandebril
by Federico Poloni 04 Apr '17

04 Apr '17

Giorno: Lunedi' 10 Aprile Ora: 11:00 Luogo: Aula Seminari, Dip.to di Matematica Speaker: Raf Vandebril, KU Leuven Titolo: Eigenvalues and eigenvectors of matrix polynomials === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Seminario Michele Benzi in SNS
by Federico Poloni 21 Mar '17

21 Mar '17

Carissimi, mi segnala Giancarlo Bigi che giovedì prossimo 23 marzo alle ore 14:30 ci sarà un seminario di Michele Benzi alla Scuola Normale: Fast iterative solution methods for the incompressible Navier-Stokes equations Giovedì, 23 Marzo 2017 Ore 14:30 Aula Maria Curie (SNS) Michele Benzi (Emory University) http://www.sns.it/seminari/fast-iterative-solution-methods-incompressible-n… (Abstract su http://www.sns.it/sites/default/files/allegati/15-03-2017/2017_03_23_benzi.…) Arrivederci, -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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workshop a Pisa, "matrix equations and tensor techniques"
by Federico Poloni 01 Feb '17

01 Feb '17

Ciao, il prossimo Febbraio al polo Fibonacci organizziamo uno workshop di due giorni, chiamato matrix equations and tensor techniques. All'edizione precedente a Bologna c'erano diversi partecipanti e speaker anche dall'estero (http://mett15.dm.unibo.it/schedule.html), e ci aspettiamo qualcosa di simile anche quest'anno. Se siete interessati a partecipare, o anche a sottomettere un talk, vi invitiamo a registrarvi (gratuitamente) su http://delone.dm.unipi.it/mett17. La scadenza per sottomettere talk è il 4 dicembre, quella per registrarsi è il 27 gennaio. Un saluto, -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Call for Papers DAPS: Data Mining for Science of Success
by Luca Pappalardo 13 Jul '16

13 Jul '16

*Call for papers* *DAPS2016: The First International Workshop on Data mining for the Analysis of Performance and Success*, in conjunction with the IEEE International Conference on Data Mining (ICDM) Website: http://kdd.isti.cnr.it/daps2016/ Date: December 12, 2016, Barcelona, Spain The increasing availability of Big Data provides an unprecedented opportunity to explore the patterns underlying success. From the strategies followed by successful sportsmen to the emergence of runaway videos on YouTube, from popularity in social media to rising starts in the scientific enterprise, from widespread technologies to groundbreaking innovations, there is wealth of data that can be explored to answer common questions: How can we measure performance? What are the common patterns of success? How did successful individuals and products get to the top? What are the principles driving the dynamics of success? These are the challenging questions at the core of the emerging *Science of Success*, an interdisciplinary field that is attracting scientists from different scientific backgrounds. The purpose of this workshop is to bring together researchers from a variety of areas, all working on the problem of analyzing and understanding the patterns of success, though from different angles. The aim is to discuss: 1) the recently developed machine learning and data mining techniques that can be leveraged to address challenges in analyzing performance and success, and 2) starting from challenges in analyzing performance and success, the practical research directions in the machine learning and data mining community. The best papers of the workshop will be invited to contribute to a special issue on "Performance and Success" edited by the journal Complexity. For more information visit the workshop website: http://kdd.isti.cnr.it/daps2016, and the ICDM conference website: http://icdm2016.eurecat.org/. You can follow news about DAPS2016 on Twitter (@DAPSworkshop) and Facebook (https://www.facebook.com/DAPSworkshop/) *Important Dates:* - *Paper Submission: August 01, 2016, 23:59 PST* - Notification: September 13, 2016 - Camera ready: September 20, 2016 - Workshop: December 12, 2016 *Topics of interest:* We encourage submissions on all theoretical and practical aspects, as well as experimental studies of deployed systems. Topics of interest to the workshop include, but are not limited to, the following subject categories: - Science of Success - Big Data sources for performance and success - mathematical models of success, performance and their interplay - ranking algorithms for performance and success - patterns of success in the scientific enterprise - popularity dynamics of popularity ion social media (hashtags, viral videos, etc.) - definition and analysis of success in social networks - measures of performance and success in sports - data mining for sports analytics - anomaly, doping and fraud detection in sports performance - patterns of success in visual arts, music and writing - adoption, diffusion and success of innovations, products and technologies - novel approaches for detecting innovators and influencers - novel approaches for performance sensing and analysis - design of predictive models for performance and success - opinion mining and sentiment analysis to quantify success in social media - career success and longevity in different professions - analysis of collective success, and well-being, and development - mathematical models of success, performance and their interplay - role of networks in success *Contact information:* For problems or questions, please do not hesitate to contact the workshop organizers by email: - Luca Pappalardo: lpappalardo(a)di.unipi.it - Paolo Cintia: paolo.cintia(a)isti.cnr.it - Roberta Sinatra: sinatrar(a)ceu.edu

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Optimization & Numerical Analysis seminars: Flores-Bazan
by Federico Poloni 23 Jun '16

23 Jun '16

Speaker: Fabián Flores Bazán Affiliation: Departamento de Ingeniería Matemática, Universidad de Concepción, Chile Time and date: Monday, 4th July 2016, 15:00 Place: Sala Seminari Est, Dipartimento di Informatica, Università di Pisa Title: A semi-infinite programming approach for the circular conic StQOP: strong duality, optimality and hidden convexity Abstract: Many formulations of quadratic allocation problems, portfolio optimization problems, the maximum weight clique problem, among others, take the form as the well-known standard quadratic optimization problem, which consist in minimizing a homogeneous quadratic function on the usual simplex in the non negative orthant. We propose to analyze the same problem when the simplex is substituted by a convex and compact base of any pointed, closed, convex (possibly circular) cone. It is associated three main duals (for which a semi-infinite formulation of the primal problem is required) and establish some characterizations of strong duality with respect to each of the three duals in terms of copositivity of the Hessian of the quadratic objective function on suitable cones. Such a problem reveals a hidden convexity. Part of the results were obtained jointly with G. Cárcamo and S. Caro. This research is supported in part by CONICYT-Chile through FONDECYT 115-0973 and BASAL projects, CMM, Universidad de Chile. === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Optimization & Numerical Analysis seminars: Romani
by Federico Poloni 20 Jun '16

20 Jun '16

Speaker: Francesco Romani Affiliation: Scuola Normale Superiore, Pisa Time: Monday, 20 June 2016, h. 10:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Algoritmi adattivi per il Clustering convesso e non convesso basato sulla NMF simmetrica Abstract: Vengono presentati algoritmi adattivi basati sulla fattorizzazione simmetrica non negativa di matrici sia per il caso di cluster con inviluppo convesso che di cluster qualsiasi. A parte il calcolo delle distanze tra i punti, gli algoritmi non fanno uso di nozioni geometriche. Lavoro congiunto con Paola Favati (CNR), Grazia Lotti (Università di Parma), Ornella Menchi http://pages.di.unipi.it/fpoloni/files/seminari/romani.doc === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Reminder: Seminario Clustering
by Francesco Romani 20 Jun '16

20 Jun '16

Speaker: Francesco Romani Time: Monday, 20 June 2016, h. 10:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Algoritmi adattivi per il Clustering convesso e non convesso basati sulla NMF simmetrica Lavoro congiunto con Paola Favati (CNR), Grazia Lotti (Università di Parma), Ornella Menchi ____________________________ Prof. Francesco Romani Dipartimento di Informatica Via Buonarroti 2, 56127 PISA, ITALY Tel +39-050-2212734 FAX +39-050-2212726 http://www.di.unipi.it/~romani

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Fwd: Reminder: Seminario Clustering
by Francesco Romani 20 Jun '16

20 Jun '16

Speaker: Francesco Romani Time: Monday, 20 June 2016, h. 10:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Algoritmi adattivi per il Clustering convesso e non convesso basati sulla NMF simmetrica Lavoro congiunto con Paola Favati (CNR), Grazia Lotti (Università di Parma), Ornella Menchi

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Reminder: Optimization & Numerical Analysis seminars: Brugiapaglia
by Federico Poloni 20 Jun '16

20 Jun '16

Speaker: Simone Brugiapaglia Affiliation: Politecnico di Milano --- Laboratory for Modeling and Scientific Computing MOX Time: Tuesday, December 15, 11 am Place: Sala Seminari Est, Dipartimento di Informatica, Università di Pisa Title: CORSING: Sparse approximation of PDEs based on Compressed Sensing Abstract: We present a novel method for the numerical approximation of PDEs, motivated by recent developments in sparse representation, and particularly by compressed sensing. We named this approach CORSING (COmpRessed SolvING). Establishing an analogy between the sampling of a signal and the Petrov-Galerkin discretization of a PDE, the CORSING method can recover the best s-term approximation to the solution with respect to N suitable trial functions, with s<<N, by evaluating the bilinear form associated with the PDE against a randomized choice of m<<N test functions. This yields an underdetermined m x N linear system, that is solved by means of sparse optimization techniques. A theoretical analysis of the CORSING procedure is presented, based on the concepts of local a-coherence and restricted inf-sup property, along with numerical experiments that confirm the robustness and reliability of the proposed strategy. === Everyone is welcome! -- --federico poloni

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Fwd: cancellazione seminario
by Dario A. Bini 30 May '16

30 May '16

Mi dispiace dovere annunciare la cancellazione del seminario di Stefano Serra Capizzano previsto oggi alle 11:00. Purtroppo nel viaggio di rientro dagli USA, per un guasto all'aereo per Austin, Stefano ha perso la coincidenza da new York per Roma. Dario

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Avviso di Seminario
by Dario A. Bini 30 May '16

30 May '16

Speaker: Stefano Serra Capizzano, Universita' dell'Insubria Titolo: Spettri, Matrici e Applicazioni nella Approssimazione di Equazioni alle Derivate Parziali Abstract: La presentazione è volta ad illustrare come dedurre informazioni sullo spettro di matrici provenienti dalla approssimazione numerica di equazioni alle derivate parziali: il secondo passo, di interesse squisitamente numerico, consiste nell'impiegare l'informazione ottenuta per il 'design' di metodi efficienti per il calcolo della soluzione dei risultanti sistemi lineari di grandi dimensioni. La chiacchierata, molto informale, includerà una breve discussione su alcuni problemi applicativi. Data: 30 Maggio 2016, ore 11:00 Luogo: Sala riunioni, Dipartimento di Matematica

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Fwd: [Dipartimento.di] Mauriana Pesaresi Seminar Update
by Federico Poloni 11 May '16

11 May '16

Scusate il nuovo messaggio ma c'è un cambio di location per il seminario che vi ho appena inoltrato. -f -------- Forwarded Message -------- Subject: [Dipartimento.di] Mauriana Pesaresi Seminar Update Date: Wed, 11 May 2016 17:34:43 +0200 From: Marco Grandi <marco.grandi(a)di.unipi.it> To: dipartimento(a)di.unipi.it Dear all, the location of tomorrow's Mauriana Pesaresi Seminar has been changed from East Seminar Room to Open Lab. Below updated information on the seminars. Speaker: Giulio Masetti Date: 12 May 2016, 13:00 Place: Open Lab (Room 306) Marco Grandi ______________________________________________ Dipartimento.di mailing list Dipartimento.di(a)listgateway.unipi.it http://listgateway.unipi.it/mailman/listinfo/dipartimento.di

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Fwd: [Dipartimento.di] Mauriana Pesaresi Seminar
by Federico Poloni 11 May '16

11 May '16

Inoltro questo avviso di seminario che sembra di argomento interessante per gli iscritti alla lista. -federico -------- Forwarded Message -------- Subject: [Dipartimento.di] Mauriana Pesaresi Seminar Date: Wed, 11 May 2016 10:53:01 +0200 From: Francesca Pratesi <pratesi(a)di.unipi.it> Organization: University of Pisa To: dottorandi(a)di.unipi.it, dipartimento(a)di.unipi.it Dear all, I would like to remind you that the next Mauriana Pesaresi Seminar will be held tomorrow, 12 May. Below further information on the seminars. Title2: Impact of Equations Ordering on Inexact and Quasi-Inverse Newton Methods. Speaker2: Giulio Masetti Date2: 12 May 2016, 13:00 Place2: East Seminar Room Abstract2: The Newton-Raphson method has a prominent role in applied science and engineering. Our research group at SEDC lab., ISTI/CNR, is involved in dependability-related assessment of Smart Electrical Grids and the Newton-Raphson method is used to solve numerically the system of power-flow equations that characterize the electrical network. In general, given a system of non-linear equations written in the form F(u)=0, where F is a continuously differentiable function that maps a n-dimensional vector u to a n-dimensional vector F(u), one of the solutions can be found via the Newton-Raphson method. At each iteration of this method, a linear system that involves the Jacobian matrix J_{F}(u) of F has to be solved and the equation ordering does not affect it. At increasing the size of the problem, solving with a direct method the linear system is often impractical (w.r.t. time and space complexity, and accuracy), even if the Jacobian is a sparse matrix. Therefore, in these cases iterative methods have been studied, where, the equation ordering becomes a critical aspect to analyse carefully. Studies related to equations ordering are available on techniques employed in medium-size linear systems, such as the Gauss-Seidel method. In this method, at each iteration, permutations of Jacobian rows and columns, that do not depend on the initial equation ordering, are exploited to gain in CPU time. Jacobian-free techniques, developed to solve very large linear problems, offer interesting opportunities for investigations on the impact of initial equations ordering over the number of iterations. One of the most effective algorithms in this category is the Inexact-Newton-Krylov: it gets rid of the Jacobian matrix and approximates the matrix-vector product J_{F}(u)v with the finite difference [F(u+sv)-F(u)]/s. Another variant of Newton- Raphson is the Quasi-Inverse-Newton: it approximates the inverse of the Jacobian J_{F}^{-1}(u) with a diagonal matrix and solves directly the linear system. A seminal article, written by L. Dutto and published on the International Journal for Numerical Methods in Engineering in 1993, numerically presents the influence of initial ordering over the preconditioner of Inexact- Newton-Krylov GMRES, and then on the number of iterations. However, it does not address the impact of ordering on the core of the method, that is the adopted Jacobian-free techniques. To go further such existing results, our study focuses on Jacobian- free methods and explores the influence of the initial ordering over them. In this talk, we discuss our approach to prove that the initial equations ordering affects Inexact-Newton-Krylov and Quasi- Inverse-Newton, also presenting a preliminary analysis to quantify the resulting impact. A trivial bivariate function will be used as case study and numerical experiments will be presented. Interestingly, the equations ordering does not only affect the efficiency in reaching a solution, but also the solution itself. As next step, we are working on exploring more realistic scenarios in the power grid domain. Traditionally, the characteristics of the domain at hand has influenced the application of mathematical structures. For example, when using Gauss-Seidel in the power-flow context, there exists a particular initial ordering such that the Jacobian is a four-block matrix and each block corresponds to well defined electrical quantities. Using Jacobian-free methods the application-oriented initial equations ordering could not be the best choice with respect to iterations number and reachable solutions. We believe this is an important feature, that the user of these methods need to be aware of. -- Francesca Pratesi Ph.D. Student - University of Pisa Room 296a - Phone 050 2212731 Department of Computer Science, Largo B. Pontecorvo 3, 56127 Pisa ______________________________________________ Dipartimento.di mailing list Dipartimento.di(a)listgateway.unipi.it http://listgateway.unipi.it/mailman/listinfo/dipartimento.di

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Funerali
by Francesco Romani 09 May '16

09 May '16

Il funerali della madre di Grazia Lotti sono domani alle 11 alla cappella del cimitero della Misericordia. Francesco. ____________________________ Prof. Francesco Romani Dipartimento di Informatica Via Buonarroti 2, 56127 PISA, ITALY Tel +39-050-2212734 FAX +39-050-2212726 http://www.di.unipi.it/~romani

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Optimization & Numerical Analysis seminars: Massei
by Federico Poloni 27 Apr '16

27 Apr '16

(This message also serves as a reminder that Claudio Sterle's seminar on "Flow intercepting facility location routing problem: formulation and branch-and-cut solving approach" is scheduled in two days: Friday, 29 April 2016, h. 14:30. ) Speaker: Stefano Massei Affiliation: Scuola Normale Superiore, Pisa Time: Thursday, 5 May 2016, h. 10:00 Place: Sala Seminari Est, Dipartimento di Informatica, Università di Pisa Title: Numerical quasiseparable preservation in matrix functions and in the cyclic reduction Abstract: The quasiseparable structure can be efficiently exploited - in order to speed up computations and storage - by using hierachical representations. This theme has raised much interest in the last two decades, in particular in the context of elliptic partial differential equations, matrix functions and Sylvester equations. Our aim is to provide a framework for the analysis of the off-diagonal singular values, focusing on the structures that can ensure an exponential decay of them. We see how this structures appears in the computation of matrix functions and in the execution of the cyclic reduction paving the way for a theoretical understanding of the preservation of the quasiseparable rank. We provide family of bounds that highlight which parameters of the model can affect the rate of decay. Finally, we show how to practically exploit the low quasiseparable rank using hierarchical matrices. === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Optimization & Numerical Analysis seminars: Sterle
by Federico Poloni 14 Apr '16

14 Apr '16

Speaker: Claudio Sterle Affiliation: University “Federico II” of Naples Time: Friday, 29 April 2016, h. 14:30 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Flow intercepting facility location routing problem: formulation and branch-and-cut solving approach Abstract: In the last ten years the research activity on location-routing problem (LRP) has significantly increased and many effective exact and approximated approaches have been presented for its solution. Following from this, great attention has been also devoted to several variants of the LRP, most of them coming from real applications. In particular, with reference to the city logistic (CL) context, several variants of the LRP have been proposed to design single-tier and two-tier freight distribution systems. In this case, LRP location decisions concern the number and position of one or more types of logistic facilities, whereas, routing decisions, concern the definition of dedicated or multi-stop routes of homogeneous or heterogeneous vehicle fleets. However most of the present literature deals with single-commodity LRP, whereas the multi-commodity case is still scarcely investigated. This issue can assume an important role in LRP real applications and in particular in the CL context. Indeed the freight to be distributed in an urban area are highly heterogeneous and consequently the problem is inherently multi-commodity. In order to contribute to fill this gap, an original formulation for the multi-commodity LRP is presented. The problem is referred to as the flow intercepting facility location-routing problem (FIFLOR), since its formulation is obtained merging the flow intercepting facility location and the vehicle routing models. A branch-and-cut algorithm for its solution is described and results obtained on test instances reproducing different urban network topologies are discussed. === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Reminder: Optimization and numerical analysis seminars
by Federico Poloni 08 Apr '16

08 Apr '16

Speaker: Yaroslav D. Sergeyev Affiliation: Università della Calabria and N.I. Lobachevsky University of Nizhni Novgorod, Russia. Time: Monday, 11 April 2016, 15:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Lipschitz global optimization Abstract: http://pages.di.unipi.it/fpoloni/files/seminari/Sergeyev.pdf and Time: Tuesday, 12 April 2016, 12:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: The Infinity Computer and numerical computations with infinities and in infinitesimals Abstract: http://pages.di.unipi.it/fpoloni/files/seminari/Sergeyev_Infinity.pdf === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Cena di giovedì 7 Aprile
by massei＠student.dm.unipi.it 05 Apr '16

05 Apr '16

Cari tutti, in occasione della partenza di Raf Vandebril e come scusa per stare un po' insieme, si pensava di fare una cena giovedì sera alla trattoria di Montemagno [1]. Chi ha piacere di partecipare è ben accetto. Dovreste però comunicarmi chi viene e se ha un mezzo a disposizione, così prenoto e ci organizziamo per raggiungere il posto. A presto e buona giornata, Stefano [1] https://www.tripadvisor.it/Restaurant_Review-g580236-d1867657-Reviews-Tratt…

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Optimization & Numerical Analysis seminars: Sergeyev
by Federico Poloni 30 Mar '16

30 Mar '16

Speaker: Raf Vandebril Affiliation: KU Leuven Time: Thursday, April 7, h. 10:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: A framework for structured linearizations of matrix polynomials in various bases Abstract: We present a framework for the construction of linearizations for scalar and matrix polynomials based on dual bases which, in the case of orthogonal polynomials, can be described by the associated recurrence relations. The framework provides an extension of the classical linearization theory for polynomials expressed in non-monomial bases and allows to represent polynomials expressed in product families, that is, as a linear combination of elements of the form $\phi_i(x) \psi_j(x)$, where $\{ \phi_i(x) \}$ and $\{ \psi_j(x) \}$ can either be polynomial bases or polynomial families which satisfy some mild assumptions. We show that this general construction can be used for many different purposes. Among them, we show how to linearize sums of polynomials and rational functions expressed in different bases. As an example, this allows to look for intersections of functions interpolated on different nodes without converting them to the same basis. === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Optimization & Numerical Analysis seminars: Sergeyev (II)
by Federico Poloni 24 Mar '16

24 Mar '16

Speaker: Yaroslav D. Sergeyev Affiliation: Università della Calabria and N.I. Lobachevsky University of Nizhni Novgorod, Russia. Time: Tuesday, 12 April 2016, 12:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: The Infinity Computer and numerical computations with infinities and in infinitesimals Abstract: The lecture presents a recent methodology allowing one to execute numerical computations with finite, infinite, and infinitesimal numbers on a new type of a computer – the Infinity Computer – patented in EU, USA, and Russia (see [23]). The new approach is based on the principle ‘The whole is greater than the part’ (Euclid’s Common Notion 5) that is applied to all numbers (finite, infinite, and infinitesimal) and to all sets and processes (finite and infinite). It is shown that it becomes possible to write down finite, infinite, and infinitesimal numbers by a finite number of symbols as particular cases of a unique framework different from that of the non-standard analysis [...] http://pages.di.unipi.it/fpoloni/files/seminari/Sergeyev_Infinity.pdf === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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Optimization & Numerical Analysis seminars: Sergeyev
by Federico Poloni 17 Mar '16

17 Mar '16

Speaker: Yaroslav D. Sergeyev Affiliation: Università della Calabria and N.I. Lobachevsky University of Nizhni Novgorod, Russia. Time: Monday, 11 April 2016, 15:00 Place: Sala Seminari Ovest, Dipartimento di Informatica, Università di Pisa Title: Lipschitz global optimization Abstract: Global optimization is a thriving branch of applied mathematics and an extensive literature is dedicated to it (see e.g., [1–24]). In this lecture, the global optimization problem of a multidimensional function satisfying the Lipschitz condition over a hyperinterval with an unknown Lipschitz constant is considered. It is supposed that the objective function can be “black box”, multiextremal, and non-differentiable. It is also assumed that evaluation of the objective function at a point is a time-consuming operation. Many algorithms for solving this problem have been discussed in literature. They can be distinguished, for example, by the way of obtaining information about the Lipschitz constant and by the strategy of exploration of the search domain. Different exploration techniques based on various adaptive partition strategies are analyzed. [...] http://pages.di.unipi.it/fpoloni/files/seminari/Sergeyev.pdf === Everyone is welcome! -- --federico poloni Dipartimento di Informatica, Università di Pisa http://www.di.unipi.it/~fpoloni/ tel:+39-050-2213143

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