Author Archives: Stephanie Lai

Our Alumni – Vanni Noferini

In this blog post, we asked one of our alumni, Vanni Noferini, a few questions about his time with the Numerical Linear Algebra Group.

Please can you introduce yourself and tell us a bit about your experience before attending University of Manchester?

I was born in Florence, Tuscany. I did my undergraduate studies there, obtaining an M.Sc. in Theoretical Physics. Later, I got my Ph.D in Mathematics in Pisa. During my PhD I was jointly supervised by Dario Bini and Luca Gemignani. While in Italy I also played volleyball at a somewhat competitive level, and I have had a number of part-time/student jobs. For example I have been writing science popularisation articles for a Swiss newspaper.

Why did you choose to do your postdoc in Manchester?

While I was writing my PhD thesis I had applied to an open call for a postdoc position to work on functions of a matrix, with Nick Higham. Nick is a world-famous superstar in the area, so that sounded like a great opportunity. Moreover, I liked Nick and Françoise, and the rest of the group, since the day of my interview; they probably have also not disliked me too much because I was offered the job. Accepting it was a great decision: I learnt a lot and my time there has certainly shaped my career to a significant extent. I started in September 2012 (technically as a predoc: I flew to Pisa to defend my viva in October 2012) and stayed until August 2015.

During my Manchester years, I have worked not only with Nick but also with many other people who then were in the group: for example Yuji Nakatsukasa, Javi Perez, Meisam Sharify, Françoise Tisseur. Plus there were other fantastic mathematicians around to talk with, such as Stefan Guettel or Martin Lotz  — not to mention the frequent international visitors. Those were the days and Manchester was just the place to be… Now I manage my own research group at Aalto, and I am doing my best to create a similarly fruitful environment: my inspiration for this goal is definitely the NLA group in Manchester during my postdoc!

How did you find Manchester?

A little humid, but fun.  In my first couple of weeks I actually stayed in the Peak District (the husband of a friend of my then girlfriend had rented me a room in Congleton, Cheshire) which was beautiful but would not have been a very convenient long-term address to work in the Alan Turing Building. Thus, I soon moved to Didsbury and I lived there for most of my 3 years in Manchester. I was living in Austin Drive, not far from the Burnage railway station, and apparently very close to where Charles Van Loan had stayed during his own Manchester postdoc (at least, so he once told me). Later, more NLA group members figured out that Didsbury was a rather nice place, so eventually we had grown a small community there. In fact, fellow Didsbury resident Martin Lotz and I used to refer to Manchester as “Greater Didsbury”. On the occasional sunny weekends I liked to go around by car, so I got to know quite well the broader area of Greater Dids… I mean, Manchester, and North-West England.

Can you tell us about your career since leaving University of Manchester?

I have continued a career in academia. I was a Lecturer (Research) at the University of Essex in Colchester for about 4 years. I obtained tenure in Essex, and also indefinite leave to remain in the UK post-Brexit, having got a “settled status” as a long-enough UK resident and EU citizen. However, even though I have enjoyed my 7 years in England, I was offered an attractive position from Aalto University (Finland), that would give me more research time and better funding opportunities. So I moved here in May 2019.

What is your current role?

Currently I am an Associate Professor in Mathematics at Aalto University, which is located in Espoo (Finland). Here I am the leader of a research group on matrix theory and its applications. At the time of this interview, my group includes one visiting professor (Paul Van Dooren), two postdocs (Giovanni Barbarino and Manme Quintana), two PhD students (Lauri Nyman and Ryan Wood) and one MSc student by research (Antti Haavikko). We are having fun!

Numerical Linear Algebra Group Activities 2021

The Numerical Linear Algebra Group had a busy year in 2021, despite the pandemic limiting our travel. This post summarizes what we got up to. Publications are not included here, but many of them can be found on MIMS EPrints under the category Numerical Analysis; see also these news stories about our publications.


Nick Higham and Manta Mikaitis released Anymatrix: a MATLAB toolbox that provides an extensible collection of matrices, organized in groups, with the ability to search the collection by matrix properties. See this blog post by Nick and this blog post by Mantas.

We make our research codes available as open source, principally on GitHub; see the repositories of ConnollyFasiHighamLiu, Mikaitis, PraneshZounon.

We also put MATLAB software on MATLAB Central File Exchange and on our own web sites, e.g., the Rational Krylov Toolbox (RKToolbox).

PhD Students

We welcomed new PhD students Ayana Mussabayeva and Alban Bloor Riley.

Thomas McSweeney (Scheduling with Precedence Constraints in Heterogeneous Parallel Computing) and Gian Maria Negri Porzio (Nonlinear Eigenvalue Problems: Theory and Algorithms) successfully defended their PhD dissertations.

Postdoctoral Research Associates (PDRAs)

Srikara Pranesh left the group in October 2021 and is now working at V-Labs in Bengaluru. He joined us in 2017 to work on the NLAFET  (Parallel Numerical Linear Algebra for Extreme Scale Systems) project and then moved onto the ICONIC project.

Mawussi Zounon left the group in June 2021 to become a senior software engineer at Arm Manchester. He joined us in 2016 to work on the NLAFET project. At the end of the NLAFET project, he continued working with the Numerical Linear Algebra Group as a Knowledge Transfer Partnership (KTP) associate, in partnership with NAG. The KTP, which ended in June 2021, was deemed “Outstanding” by the KTP Grading Panel for its achievement in meeting the KTP Objectives.

Ian McInerney joined the group in December 2021, having completed his PhD in the High Performance Embedded and Distributed Systems (HiPEDS) Centre for Doctoral Training at Imperial College, London, under the supervision of Eric Kerrigan and George Constantinides.


Nick Higham and Françoise Tisseur received funding for work on multi-precision algorithms from Lawrence Livermore National Laboratory under the Exascale Computing Project.

Françoise Tisseur received EPSRC funding to work on mixed precision symmetric eigensolvers.

Presentations at Conference and Workshops

SIAM Conference on Computational Science and Engineering (virtual), March 1-5: Connolly, Fasi, Higham, Mikaitis, Pranesh, Tisseur.

SIAM Conference on Applied Linear Algebra (virtual), May 17-21: Fasi, Liu.

New Directions in Numerical Linear Algebra and High Performance Computing (virtual) July 7-8, 2021: Hammarling, Higham, Tisseur.

SIAM Annual Meeting 2021(virtual), July 19-23: Connolly, Fasi, Higham, Mary, and Pranesh.

IEEE International Conference on Data Mining (ICDM) 2021, Auckland, New Zealand (virtual), December 7-10: Chen

Conference and Workshop Organization

Stefan Güttel continued to co-organize the E-NLA online seminar series dedicated to topics in Numerical Linear Algebra.

Nick Higham organized a minisymposium on Reduced Precision Arithmetic and Stochastic Rounding at the SIAM Conference on Computational Science and Engineering,  March 1-4, 2021.

Theo Mary and Srikara Pranesh organised a two-part minisymposium on Mixed Precision Algorithms for High Performance Scientific Computingr at the SIAM Conference on Computational Science and Engineering, March 1-5, 2021.

Massimiliano Fasi and Xiaobo Liu organised a two-part minisymposium on Computing Functions of Matrices at the SIAM Conference on Applied Linear Algebra, May 17-21, 2021.

Sven Hammarling, Nick Higham and Françoise Tisseur organized the New Directions in Numerical Linear Algebra and High Performance Computing workshop which was held virtually on July 7-8, 2021, celebrating the 70th birthday of Jack Dongarra. Videos from the workshop are available here.

Rob Corless and Nick Higham organized a two-part minisymposium Bohemian Matrices and Applications at the SIAM Annual Meeting (virtual), July 2021.

Nick Higham and Sri Pranesh organized a two-part minisymposium Computational Frontiers in Numerical Linear Algebra at the SIAM Annual Meeting (virtual), July 2021.

Max Fasi was on the organizing committee of the the 9th Matrix Equations and Tensor Techniques Workshop9-10 September 2021 in Perugia, Italy.

Recognition and Service

Nick Higham was been named a 2020 ACM Fellow.

Stefan Güttel was awarded the 2021 James H. Wilkinson Prize in Numerical Analysis and Scientific Computing.

Nick Higham received the George Pólya Prize for Mathematical Exposition from the Society for Industrial and Applied Mathematics (SIAM).

Nick Higham was awarded the 2022 Hans Schneider Prize by the International Linear Algebra Society (ILAS).

External Members

Max Fasi took up a Lectureship in Computer Science at Durham University in October 2021.

Nick Higham Featured in People of ACM

Professor Nick Higham is featured in a People of ACM profile. “People of ACM” is a bulletin at the Association for Computer Machinery (ACM) highlighting “the unique scientific accomplishments and compelling personal attributes of ACM members who are making a difference in advancing computing as a science and a profession”.

Professor Jack Dongarra was also featured in People of ACM in 2013.

Professor Nicholas J. Higham, University of Manchester

Nick Higham Awarded the 2022 Hans Schneider Prize

Professor Nick Higham has been awarded the 2022 Hans Schneider Prize by the International Linear Algebra Society (ILAS). The Hans Schneider Prize in Linear Algebra is awarded every three years by ILAS for research, contributions, and achievements at the highest level of Linear Algebra.

Nick is cited for his fundamental contributions in the analysis of a wide range of numerical linear algebra problems and matrix functions. He will present his lecture at the 25th ILAS Conference in Madrid, Spain, June 5-9, 2023.


Professor Nicholas J. Higham, The University of Manchester

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NLA Group Presentations at SIAM Annual Meeting 2021

Members of the Numerical Linear Algebra Group will be giving six presentations at the upcoming SIAM Annual Meeting (AN21). They are also organizing the two-part minisymposiums Computational Frontiers in Numerical Linear Algebra (Part 1, Part 2) and Bohemian Matrices and Applications (Part 1, Part 2).

The conference will be held virtually, from 19th July to 23rd July, 2021.

Here are the dates and times (listed in Eastern Time (UTC-4)) where members of our group will be giving their presentations:

Tuesday 20 July
18:30 – 20:30 Massimiliano Fasi
Cpfloat: A C Library for Emulating Low-Precision Arithmetic (poster)

Wednesday 21 July
14:30 – 15:30 Nick Higham
Past President’s Address – Mixed Precision Numerical Linear Algebra with More Realistic Error Bounds

Thursday 22 July
16:45 – 17:10 Massimiliano Fasi
Determinants of Normalized Bohemian Upper Hessenberg Matrices

Friday 23 July
10:15 – 10:40 Theo Mary
Data-Aware Mixed Precision Algorithms
10:45 – 11:10 Srikara Pranesh 
Random Matrices Generating Large Growth in LU Factorization with Pivoting
11:15 – 11:40 Michael Connolly
Mixed Precision Randomized SVD

More information on AN21 is available here.

Nick Higham Awarded the SIAM George Pólya Prize for Mathematical Exposition

The Society for Industrial and Applied Mathematics (SIAM) has chosen Nick Higham, Royal Society Research Professor and Richardson Professor of Applied Mathematics, as the 2021 recipient of the George Pólya Prize for Mathematical Exposition.

The prize, which is awarded for expository work that communicates mathematics effectively, is named after George Pólya, the Hungarian mathematician who wrote the million-selling book How to Solve It, first published in 1945.

“Pólya was a brilliant researcher, teacher, and expositor of mathematics,” said Higham. “It is an honor to receive this SIAM prize named after him, especially as most of my research and expository writing has been published with SIAM.”

Higham was cited for “the crisp clarity, elegance and accessibility of his mathematical and popular exposition on a broad range of topics in applied mathematics.”

The award ceremony will be held at the 2021 SIAM Annual Meeting, scheduled to be held in a virtual format during July 19-23, 2021. See also the SIAM announcement of the award.

Professor Nicholas J. Higham, University of Manchester. Photo: Rob Whitrow

The BLAS named as one of the “Ten Codes that Transformed Science”

By Sven Hammarling.

An article in a recent issue of the journal Nature has the title “Ten Codes that Transformed Science”.

Two of the codes are purely numerical, namely the fast Fourier transform (FFT) and the Basic Linear Algebra Subprograms (BLAS). The BLAS evolved in three stages, the Level 1 BLAS2 for scalar and vector operations, the Level 2 BLAS3 for matrix-vector operations and the Level 3 BLAS4 for matrix-matrix operations. The first draft proposal for the Level 1 BLAS appeared in the ACM Signum Newsletter in 1973, so the project as a whole spanned about seventeen years.

Two members of the Numerical Linear Algebra Group were directly involved in the development of the BLAS. Jack Dongarra wrote a number of the Level 1 BLAS routines, was involved in testing the routines on an IBM 370/195 and provided several efficient implementations of the routines, all of which was acknowledged in the published paper. Both Jack Dongarra and Sven Hammarling were authors of the Level 2 and 3 BLAS, together with Jeremy Du Croz and Richard Hanson for the Level 2 BLAS, and Jeremy Du Croz and Iain Duff for the Level 3 BLAS.

To take two quotes by Jack Dongarra from the Nature article:

“In effect, BLAS reduced matrix and vector mathematics to a basic unit of computation as fundamental as addition and subtraction … It provides the fabric on which we do computing.”

As well as providing a standard interface, it was hoped that computer manufacturers would provide optimised implementations and that hope has certainly been realised.

It should be said that the BLAS were very much a community project, with input from many people. The BLAS, especially the Level 3 BLAS, provided the basic high performance operations, particularly for the block partitioned methods, used by the LAPACK5 project, which started in 1987, before the actual publication of the Level 3 BLAS.

More recently, driven by modern parallel machines and the desire to solve larger and larger problems, a standard for Batched BLAS (BBLAS) operations has been proposed and has been accepted for publication by ACM ToMS6. The development of the BBLAS was done by the Numerical Linear Algebra Group as part of an EU project, NLAFET7, in collaboration with Jack Dongarra’s Innovative Computing Laboratory at the University of Tennessee.

1J. M. Perkel. Ten Codes that Transformed Science. Nature, 589:344–349, January 2021.
2C. L. Lawson, R. J. Hanson, D. Kincaid, and F. T. Krogh. Basic Linear Algebra Subprograms for FORTRAN usage. ACM Trans. Math. Software, 5:308–323, 1979.
3J. J. Dongarra, J. Du Croz, S. Hammarling, and R. J. Hanson. An extended set of FORTRAN Basic Linear Algebra Subprograms. ACM Trans. Math. Software, 14:1–32, 399, 1988.
4J. J. Dongarra, J. Du Croz, I. S. Duff, and S. Hammarling. A set of Level 3 Basic Linear Algebra Subprograms. ACM Trans. Math. Software, 16:1–28, 1990.
5E. Anderson, Z. Bai, C. H. Bischof, S. Blackford, J. Demmel, J. J. Dongarra, J. Du Croz, A. Greenbaum, S. Hammarling, A. McKenney, and D. C. Sorensen. LAPACK Users’ Guide. SIAM, Philadelphia, PA, USA, 3rd edition, 1999. ISBN 0-89871-447-8. (
6A Set of Batched Basic Linear Algebra Suprograms, ACM Trans. Math. Software. To appear.
7Deliverable D7.6, (



Nick Higham Named 2020 ACM Fellow

Professor Nick Higham has been named among the 2020 Association for Computing Machinery (ACM) Fellows, who are recognised for work underpinning contemporary computing.

The accomplishments of the 2020 ACM Fellows have driven innovations that have ushered in significant improvements across many areas of technology, industry, and personal life.

Nick has been recognised for his contributions to numerical linear algebra, numerical stability analysis, and communication of mathematics.

He is among 95 ACM Fellows, representing universities, corporations and research centres around the world, who are celebrated for their wide-ranging and fundamental contributions in areas including artificial intelligence, cloud computing, computer graphics, virtual reality, and more.

The ACM Fellows programme recognises the top 1% of ACM members for their outstanding accomplishments in computing and information technology and/or outstanding service to ACM and the larger computing community. Fellows are nominated by their peers, with nominations reviewed by a distinguished selection committee.

ACM President Gabriele Kotsis said: “The 2020 ACM Fellows have demonstrated excellence across many disciplines of computing. These men and women have made pivotal contributions to technologies that are transforming whole industries, as well as our personal lives. We fully expect that these new ACM Fellows will continue in the vanguard in their respective fields.”

Professor Nicholas J. Higham, University of Manchester

Numerical Linear Algebra Group Activities 2020

The Numerical Linear Algebra Group had a productive year in 2020, despite working remotely from March onwards because of the pandemic. This post summarizes what we got up to. Publications are not included here, but many of them can be found on MIMS EPrints under the category Numerical Analysis; see also these news stories about our publications.


Craig Lucas, Nick Higham, Xinye Chen, Steven Elsworth, Xiaobo Liu, Michael Connolly, Mantas Mikaitis, Len Freeman, Massimiliano Fasi, Pierre Blanchard, Sven Hammarling, Asad Raza Aitor Mehasi Mehasi, Stephanie Lai, Gian Maria Negri Porzio, Thomas McSweeney, Mawussi Zounon, Françoise Tisseur, Srikara Pranesh, Yuqing Zhang, Eleni Vlachopoulou, March 2020.


We make our research codes available as open source, principally on GitHub; see the repositories of ConnollyFasiHighamLiuPranesh, Tisseur, and Zounon.

We also put MATLAB software on MATLAB Central File Exchange and on our own web sites, e.g., the Rational Krylov Toolbox (RKToolbox).

PhD Students

We welcomed new PhD students Xinye Chen and Thomas Seleiro.

Steven Elsworth successfully defended his PhD thesis Rational Krylov Methods and Machine Learning Approaches to Time Series Forecasting in March 2020 .

Michael Connolly took an internship with MathWorks from July to September 2020.

Postdoctoral Research Associates (PDRAs)

Mantas Mikaitis, previously an EPSRC Doctoral Prize Fellow in the group, is now working on the ICONIC project in the group.   During the year he successfully defended his PhD thesis Arithmetic Accelerators for a Digital Neuromorphic Processor in the Department of Computer Science.

Massimiliano Fasi left the group in September 2020 and is now working at Örebro University in Sweden.

Roberto Cahuantzi  was a member of the group from March to September 2020, working with Stefan Güttel.

Recognition and Service

Jack Dongarra received the 2020 IEEE Computer Society’s Computer Pioneer Award.

Srikara Pranesh and Michael Connolly won first and second best poster prizes, respectively, at the SIAM UKIE Section Meeting, Edinburgh, January 2020.

Françoise Tisseur received the London Mathematics Society’s Fröhlich Prize.

Theo Mary received an honourable mention for the 2020 Householder Prize and the 2021 SIAG/LA Early Career Prize. He also received a grant from the Faculty of Engineering Sciences of Sorbonne University for a project on”Mixed precision algorithms for HPC”.

Sixteen publications by members of the NLA group feature among the top 40 most read articles in two SIAM journals, both leading venues for publications in numerical linear algebra.

Stefan  Güttel was awarded the 2021 James H. Wilkinson Prize in Numerical Analysis and Scientific Computing.

Nick Higham received the IMA Gold Medal 2020.

Theo Mary has been awarded the 2021 SIAG/LA Early Career Prize by the SIAM Activity Group on Linear Algebra.


Stefan Güttel’s and Nick Higham’s Alan Turing Fellowships have been extended by one year to September 2021.

Stefan Güttel received a Small Project Grant from the Alan Turing Institute.

Nick Higham and Françoise Tisseur received funding for work on multi-precision algorithms from Lawrence Livermore National Laboratory under the Exascale Computing Project.

Nick Higham and Françoise Tisseur received funding from The MathWorks, Inc. to support a PhD student to work on exploiting multiprecision arithmetic.

Massimiliano Fasi is one of the participants of the 2020 INdAM-GNCS project “Low-rank methods for linear algebra problems with data-sparse structure” funded by the Scientific Computing Group of the Istituto Nazionale di Alta Matematica “Francesco Severi”.

External Presentations

SIAM UKIE Annual Meeting 2020, Edinburgh, January 10: Connolly, Liu, Negri Porzio, Pranesh, Higham, Pranesh and Tisseur.
SIAM Conference on Parallel Processing for Scientific Computing (PP20) in Seattle, Washington, US, February 12 – 15: Fasi, Mary, Mikaitis, Pranesh and Zounon.
Theo Mary, Performance and Accuracy of Mixed-Precision Matrix Factorizations, SIAM PP20, February, 2020.
Srikara Pranesh, Point Arithmetic for the Solution of Linear System of Equations, SIAM PP20, February, 2020.
Mawussi Zounon, Opportunities for Multi Precision Computation in Memory Bound Applications, SIAM PP20, February, 2020.
Nick Higham, Are Numerical Linear Algebra Algorithms Accurate at Extreme Scale and at Low Precisions?, in E-NLA Online seminar series on Numerical Linear Algebra, April 29, 2020.
Nick Higham, Random Orthogonal Matrices in High Performance Computing, Masked Guest Speaker, King Abdullah University of Science and Technology, 2020.
Nick Higham, The Anatomy of the World’s Fastest Linear Equation Solver, Online Distinguished Lecture, The Hong Kong Polytechnic University, September 2020.
Theo Mary, Mixed Precision Low Rank Compression of Data Sparse Matrices, Communications in NLA, online, September 2020.
Nick Higham, Rehabilitating Correlations, Leicester Actuarial Science Society and Students Union Mathematical Society, 2020.
Theo Mary, Mixed precision arithmetic: hardware, algorithms and analysis, London Mathematical Society Virtual Graduate Student Meeting, November, 2020.
Nick Higham, Mathematics of today’s floating-point arithmetic, London Mathematical Society Naylor Lecture, November 20, 2020.
Françoise Tisseur, Towards Reliable Eigensolvers for Nonlinear Eigenvalue Problems, in E-NLA Online seminar series on Numerical Linear Algebra, November 25, 2020.

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