- NumPI - Mailing list — Dipartimento di Matematica, UniPI

[NOMADS] seminar - Massimiliano Fasi
by Francesco Tudisco 22 Jun '22

22 Jun '22

Dear all, You are all invited to the next NOMADS seminar on low-precision numerical computations, which will be given by Massimiliano Fasi from Durham University on Friday June 24, 2022. The seminar will take place in the GSSI’s Library, but remote participation will also be possible via the zoom link: https://us02web.zoom.us/j/89668910844?pwd=TmVwQUFoNklUajAzMlEyMzB6ZVZzUT09 Below you can find the details about his talk. Looking forward to seeing you all on Friday! – Francesco Tudisco Massimiliano Fasi (Durham University, UK) https://www.durham.ac.uk/staff/massimiliano-fasi/ Title of the talk: CPFloat: A C Library for Emulating Low-Precision Arithmetic Abstract: Low-precision floating-point arithmetic can be simulated via software by executing each arithmetic operation in hardware and rounding the result to the desired number of significant bits. For IEEE-compliant formats, rounding requires only standard mathematical library functions, but handling subnormals, underflow, and overflow demands special attention, and numerical errors can cause mathematically correct formulae to behave incorrectly in finite arithmetic. Moreover, the ensuing algorithms are not necessarily efficient, as the library functions these techniques build upon are typically designed to handle a broad range of cases and may not be optimized for the specific needs of floating-point rounding algorithms. CPFloat is a C library that offers efficient routines for rounding arrays of binary32 and binary64 numbers to lower precision. The software exploits the bit level representation of the underlying formats and performs only low-level bit manipulation and integer arithmetic, without relying on costly library calls. In numerical experiments the new techniques bring a considerable speedup (typically one order of magnitude or more) over existing alternatives in C, C++, and MATLAB. To the best of our knowledge, CPFloat is currently the most efficient and complete library for experimenting with custom low-precision floating-point arithmetic available in any language. For more information, please see: https://num-gssi.github.io/seminar/ -- You received this message because you are subscribed to the Google Groups "nomads-list" group. To unsubscribe from this group and stop receiving emails from it, send an email to nomads-list+unsubscribe(a)gssi.it. To view this discussion on the web visit https://groups.google.com/a/gssi.it/d/msgid/nomads-list/DB6PR05MB322380D250…. For more options, visit https://groups.google.com/a/gssi.it/d/optout.

1 1

Fwd: Fwd: PhD-positions at the University of Stuttgart
by Federico Poloni 13 Jun '22

13 Jun '22

Buongiorno, inoltro questo annuncio per alcuni posti di dottorato in "Numerical Analysis of domain decomposition methods" in caso conosciate qualche interessato. Federico -------- Messaggio Inoltrato -------- Oggetto: PhD-positions at the University of Stuttgart Data: Mon, 13 Jun 2022 09:03:26 +0000 Mittente: Stamm, Benjamin <best(a)acom.rwth-aachen.de> A: Benjamin.Stamm(a)ians.uni-stuttgart.de <Benjamin.Stamm(a)ians.uni-stuttgart.de> Dear colleagues, Please apologize for the mass mail. It is my pleasure to announce several openings for PhD-positions with my start at the University of Stuttgart this summer. I would be extremely grateful if you could forward this mail to interested students and post the attached flyers in your building. Of course, I will also diffuse it in a less analog manner, but I’d also like to do it the good old way ;-) Warm greetings, Ben Prof. Dr. Benjamin Stamm Applied and Computational Mathematics RWTH Aachen University Schinkelstraße 2, 52062 Aachen (Germany) Tel.: + 49 / 241 - 80 98672 (direct line) Tel.: + 49 / 241 - 80 98660 (secretary) e-mail: best(a)acom.rwth-aachen.de <mailto:best@acom.rwth-aachen.de> web: http://tinyurl.com/jv7h8n4

1 0

Math colloquium today
by Francesco Tudisco 26 May '22

26 May '22

Dear all, Please note that there was a typo in the event reminder you received earlier today. The lecture by Stefano Serra-Capizzano will take place today at 15:00 in the Main Lecture Hall, not in the Auditorium! ============== GSSI, via F Crispi 7. Room: MLH. Date: 26 May at 15:00 Stefano Serra-Capizzano, University of Insubria The GLT class as a Generalized Fourier Analysis and applications Participation is also possible via the zoom link: https://us02web.zoom.us/j/89664583638?pwd=MTluRndSWUhoMG5VbU80Rlcydmg2dz09 <https://us02web.zoom.us/j/89664583638?pwd=MTluRndSWUhoMG5VbU80Rlcydmg2dz09> Abstract Recently, the class of Generalized Locally Toeplitz (GLT) sequences has been introduced as a generalization both of classical Toeplitz sequences and of variable coefficient differential operators and, for every sequence of the class, it has been demonstrated that it is possible to give a rigorous description of the asymptotic spectrum in terms of a function (the symbol) that can be easily identified. This generalizes the notion of a symbol for differential operators also of fractional type (discrete and continuous) or for Toeplitz sequences for which it is identified through the Fourier coefficients and is related to the classical Fourier Analysis. The GLT class has nice algebraic properties and indeed it has been proven that it is stable under linear combinations, products, and inversion when the sequence which is inverted shows a sparsely vanishing symbol (sparsely vanishing symbol = a symbol which vanishes at most in a set of zero Lebesgue measure). Furthermore, the GLT class virtually includes any approximation by local methods (Finite Difference, Finite Element, Isogeometric Analysis of partial differential equations (PDEs) and, based on this, we demonstrate that our results on GLT sequences can be used in a PDE setting in various directions. For more information, please see: https://indico.gssi.it/event/394/ — Francesco Tudisco Assistant Professor School of Mathematics GSSI Gran Sasso Science Institute Web: https://ftudisco.gitlab.io <https://ftudisco.gitlab.io/> -- You received this message because you are subscribed to the Google Groups "nomads-list" group. To unsubscribe from this group and stop receiving emails from it, send an email to nomads-list+unsubscribe(a)gssi.it. To view this discussion on the web visit https://groups.google.com/a/gssi.it/d/msgid/nomads-list/66E0C4A0-72B8-4B7C-…. For more options, visit https://groups.google.com/a/gssi.it/d/optout.

1 0

[Indico] [Event reminder] The GLT class as a Generalized Fourier Analysis and applications (26/05/2022, 15:00 Europe/Rome)
by francesco.tudisco＠gssi.it 26 May '22

26 May '22

Please note that the event "The GLT class as a Generalized Fourier Analysis and applications" will start on 26 May 2022, 15:00 (Europe/Rome). It will take place at GSSI (Rectorate-Building-Auditorium). You can access the full event here: https://indico.gssi.it/e/394 Description ----------- Stefano Serra-Capizzano University of Insubria, Italy http://scienze-como.uninsubria.it/serra/ Title of the talk: The GLT class as a Generalized Fourier Analysis and applications Abstract: Recently, the class of Generalized Locally Toeplitz (GLT) sequences has been introduced as a generalization both of classical Toeplitz sequences and of variable coefficient differential operators and, for every sequence of the class, it has been demonstrated that it is possible to give a rigorous description of the asymptotic spectrum in terms of a function (the symbol) that can be easily identified. This generalizes the notion of a symbol for differential operators also of fractional type (discrete and continuous) or for Toeplitz sequences for which it is identified through the Fourier coefficients and is related to the classical Fourier Analysis. The GLT class has nice algebraic properties and indeed it has been proven that it is stable under linear combinations, products, and inversion when the sequence which is inverted shows a sparsely vanishing symbol (sparsely vanishing symbol = a symbol which vanishes at most in a set of zero Lebesgue measure). Furthermore, the GLT class virtually includes any approximation by local methods (Finite Difference, Finite Element, Isogeometric Analysis of partial differential equations (PDEs) and, based on this, we demonstrate that our results on GLT sequences can be used in a PDE setting in various directions. Detailed PDF version of the abstract: HERE The seminar will take place in the Auditorium, but remote participation will also be possible via the zoom link: https://us02web.zoom.us/j/89664583638?pwd=MTluRndSWUhoMG5VbU80Rlcydmg2dz09 Note ---- Dear all, This is just a gentle reminder that this week's Math Colloquium will take place today at 3pm in the Main Auditorium. Looking forward to seeing you all there! Best, Paolo Antonelli, Marielle Simon, Francesco Tudisco and Francesco Viola -- Indico :: Email Notifier https://indico.gssi.it/e/394 -- You received this message because you are subscribed to the Google Groups "nomads-list" group. To unsubscribe from this group and stop receiving emails from it, send an email to nomads-list+unsubscribe(a)gssi.it. To view this discussion on the web visit https://groups.google.com/a/gssi.it/d/msgid/nomads-list/165354840854.1432.1…. For more options, visit https://groups.google.com/a/gssi.it/d/optout.

1 0

[NOMADS] Seminar - Paolo Cifani
by Francesco Tudisco 24 May '22

24 May '22

Dear all, You are all invited to the following NOMADS seminar by Paolo Cifani, GSSI, which will take place Today at 13:45 in MLH and online via zoom at the following address: https://us02web.zoom.us/j/83830006962?pwd=SmI1MTVKRTllU3dBR01Ybko5bzBJdz09 <https://us02web.zoom.us/j/83830006962?pwd=SmI1MTVKRTllU3dBR01Ybko5bzBJdz09> Looking forward to seeing you all later! Nicola and Francesco ============== GSSI, via F Crispi 7. Room: MLH. Date: 24 May at 13:45 Paolo Cifani (GSSI) Geometric integration of Lie-Poisson flows on the sphere In this seminar I will touch upon the recent developments in structure-preserving (geometric) integration of Euler’s equations for two-dimensional incompressible flows. It has been known for half a century that the dynamics of incompressible ideal fluids in two dimensions can be understood as an evolution equation on the contangent bundle of the infinite-dimensional Lie group of symplectic dffeomorphisms. In particular, the vorticity equation constitutes a Lie-Poisson system characterized by an infinite number of first integrals, i.e. the integrated powers of vorticity. This set of constraints, absent in three dimensions, has profound effects on the energy transfer mechanisms across scales of motion. Yet, the construction of a numerical system which preserves this rich Poisson structure has been elusive. Most attempts either fail in fully preserving the geometric structure or have a high computational complexity. Here, I will show that, thanks to our recent advances, it possible to design a geometric integrator which embeds this fundamental principle of the continuum into the discrete system at a modest computational cost. The construction of such scheme, the main numerical algorithms and their parallelisation on modern supercomputing facilities will be discussed. Finally, an application to the spectrum of homogeneous two-dimensional turbulence will be illustrated. For more information, please see: https://num-gssi.github.io/seminar/ The seminar will take place in the Main Lecture Hall, but remote participation will also be possible via the zoom link: https://us02web.zoom.us/j/89668910844?pwd=TmVwQUFoNklUajAzMlEyMzB6ZVZzUT09 — Francesco Tudisco Assistant Professor School of Mathematics GSSI Gran Sasso Science Institute Web: https://ftudisco.gitlab.io <https://ftudisco.gitlab.io/> -- You received this message because you are subscribed to the Google Groups "nomads-list" group. To unsubscribe from this group and stop receiving emails from it, send an email to nomads-list+unsubscribe(a)gssi.it. To view this discussion on the web visit https://groups.google.com/a/gssi.it/d/msgid/nomads-list/5893E020-236E-481D-…. For more options, visit https://groups.google.com/a/gssi.it/d/optout.

1 0

[Indico] [Event reminder] The GLT class as a Generalized Fourier Analysis and applications (26/05/2022, 15:00 Europe/Rome)
by francesco.tudisco＠gssi.it 23 May '22

23 May '22

Please note that the event "The GLT class as a Generalized Fourier Analysis and applications" will start on 26 May 2022, 15:00 (Europe/Rome). It will take place at GSSI (Rectorate-Building-Auditorium). You can access the full event here: https://indico.gssi.it/e/394 Description ----------- Stefano Serra-Capizzano University of Insubria, Italy http://scienze-como.uninsubria.it/serra/ Title of the talk: The GLT class as a Generalized Fourier Analysis and applications Abstract: Recently, the class of Generalized Locally Toeplitz (GLT) sequences has been introduced as a generalization both of classical Toeplitz sequences and of variable coefficient differential operators and, for every sequence of the class, it has been demonstrated that it is possible to give a rigorous description of the asymptotic spectrum in terms of a function (the symbol) that can be easily identified. This generalizes the notion of a symbol for differential operators also of fractional type (discrete and continuous) or for Toeplitz sequences for which it is identified through the Fourier coefficients and is related to the classical Fourier Analysis. The GLT class has nice algebraic properties and indeed it has been proven that it is stable under linear combinations, products, and inversion when the sequence which is inverted shows a sparsely vanishing symbol (sparsely vanishing symbol = a symbol which vanishes at most in a set of zero Lebesgue measure). Furthermore, the GLT class virtually includes any approximation by local methods (Finite Difference, Finite Element, Isogeometric Analysis of partial differential equations (PDEs) and, based on this, we demonstrate that our results on GLT sequences can be used in a PDE setting in various directions. Detailed PDF version of the abstract: HERE The seminar will take place in the Auditorium, but remote participation will also be possible via the zoom link: https://us02web.zoom.us/j/89664583638?pwd=MTluRndSWUhoMG5VbU80Rlcydmg2dz09 Note ---- Dear all, It is our pleasure to invite you all to the next Math Colloquium on Thursday May 19 at 3pm in the Main Auditorium. The speaker will be Stefano Serra-Capizzano, from the University of Insubria (Como, Italy) with a talk on Generalized Fourier Analysis and Applications. We look forward to seeing you all there! Please feel free to share this announcement as you see fit. Best, Paolo Antonelli, Marielle Simon, Francesco Tudisco and Francesco Viola -- Indico :: Email Notifier https://indico.gssi.it/e/394 -- You received this message because you are subscribed to the Google Groups "nomads-list" group. To unsubscribe from this group and stop receiving emails from it, send an email to nomads-list+unsubscribe(a)gssi.it. To view this discussion on the web visit https://groups.google.com/a/gssi.it/d/msgid/nomads-list/165331080936.1432.1…. For more options, visit https://groups.google.com/a/gssi.it/d/optout.

1 0

Reminder: Seminario 24/5, 15:00 - Andrew Wathen
by Leonardo Robol 23 May '22

23 May '22

Cari tutti, vi ricordo il Colloquio de Giorgi di domani 24/5 alle 15:00, che sarà tenuto da Andrew Wathen. https://www.crm.sns.it/course/6307/ La registrazione per partecipare (stando a quanto indicato sul sito e sul poster, che allego) è obbligatoria per poter partecipare in presenza. -- Leonardo Robol.

1 0

Fwd: Fwd: Modern Techniques of Very Large Scale Optimization, Edinburgh, 19th - 20th May 2022
by Fabio Durastante 12 May '22

12 May '22

FYI -------- Messaggio Inoltrato -------- Oggetto: Fwd: Modern Techniques of Very Large Scale Optimization, Edinburgh, 19th - 20th May 2022 Data: Thu, 12 May 2022 17:14:04 +0100 Mittente: Stefano Cipolla <scipolla(a)ed.ac.uk> A: fabio.durastante(a)unipi.it ======================== Dear Colleagues, we are delighted to inform you that the workshop "Modern Techniques of Very Large Scale Optimization" will be held in Edinburgh, 19th - 20th May 2022; please see https://www.maths.ed.ac.uk/~gondzio/admm2020/home.html for more information. Although the capacity of in-person attendance is already reached we are happy for online participants to follow the talks. If you are interested and would like to attend the workshop online, then please register (free of charge) at your earliest convenience but not later than Friday 13th May. We will send you a Zoom link. Very Best regards, Jacek, Stefano, Filippo ======================== -- Stefano Cipolla Postdoctoral Research Associate School of Mathematics University of Edinburgh James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh, EH9 3FD email: scipolla(a)ed.ac.uk The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. Is e buidheann carthannais a th’ ann an Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336.

1 0

Fwd: CENTRO DE GIORGI -- ANNOUNCEMENT -- COLLOQUIO DE GIORGI (24 May 2022)
by Fabio Durastante 12 May '22

12 May '22

*********************************************************************************** CENTRO DI RICERCA MATEMATICA "ENNIO DE GIORGI" ********************************************************************************** COLLOQUIO DE GIORGI Centro De Giorgi, Pisa, 24 May 2022 Aula Dini: 3.00 pm The event will take place in person. Andrew Wathen University of Oxford Title:“Numerical solutions methods for problems of PDE-constrained optimisation” Abstract:Since the advent of computers there has been interest in numerical methods for solving partial differential equations (PDE) problems---both methods of approximation and numerical linear algebra for the resulting sets of equations which are usually of very large dimension. Sometimes it is the solutions themselves that are of interest, but there is a significant class of problems where there is a design optimization criterion with physical constraints that are expressed in terms of PDEs; it is always the motion of fluids described by flow equations which provide the principal constraints when an engineer designs an aerodynamic structure with minimal drag and acceptable lift for example. In this talk I will consider numerical methods for such optimization problems with PDE constraints, in particular methods of iterative numerical linear algebra that render feasible the solution of such problems on advanced computers. Web site:http://www.crm.sns.it/course/6307/ <http://www.crm.sns.it/course/6307/> Please note that for organizational purposes, registration <http://www.crm.sns.it/event/493/registration.html>is mandatory. CRM Secretariat STG Puteano Centro di Ricerca Matematica "Ennio De Giorgi" Scuola Normale Superiore Piazza dei Cavalieri, 3 56126 Pisa, Italy

1 0

Seminario di oggi (link)
by Leonardo Robol 05 May '22

05 May '22

Cari tutti/e, Il seminario di oggi sarà disponibile, oltre che in presenza, anche in streaming al solito link https://meetings.dm.unipi.it/b/leo-xik-xu4. A dopo, -- Leonardo Robol

1 0