## 2018-2019

## Past Meetings 2018-2019

### Wednesday July 31, 2019

Elisa Riccietti on “On the iterative solution of systems of the form A^TAx=A^Tb+c”. Abstract, Sildes.

### Wednesday June 19, 2019

Theo Mary on “Sharper and smaller rounding error bounds for low precision scientific computing”.

### Wednesday May 22, 2019

Conor Rogers on “Some experiments on rational approximation with noisy data”. Slides

### Wednesday May 8, 2019

Florent Lopez on “Performance and accuracy of the LU factorisation on GPU using Tensor Cores”.

Abstract: We currently observe an emergence of new hardware supporting low precision floating-point formats, such as the IEEE half precision format. This is for example the case of recent NVIDIA GPUs such as the Volta and Turing architectures that dramatically improve the performance of half-precision computations with the introduction of new processing units called Tensor Cores. In this talk we discuss the use of Tensor cores for performing a reduced precision LU factorisation and we show the benefits of exploiting such processing units both in terms of performance and accuracy compared to traditional single and half precision variants.

### Wednesday May 1, 2019

Srikara Pranesh on “Simulating Low Precision Floating-Point Arithmetic”.

### Wednesday April 3, 2019

Michael Connolly on “Multiprecision Inverse Computation”. Slides.

Abstract: In this talk we discuss the Newton-Schulz iteration for computing the generalized inverse of a matrix. We discuss numerical results arising from a multiprecision implementation of this algorithm as well as the use of a low precision solution to this problem as a preconditioner for mixed precision iterative refinement.

### Wednesday March 27, 2019

Xiaobo Liu on “Computing the Matrix Mittag-Leffler Function”. Slides.

Abstract: Similar to the matrix exponential in the solutions of linear differential equation systems, the matrix Mittag-Leffler (ML) function plays an analogous role in solving linear fractional differential equation systems, which have been proved to be the best way of modelling many physical and engineering processes in real life. In this talk, I will mainly review a recent paper for computing the matrix ML function based on the Schur-Parlett algorithm.

### Wednesday March 19, 2019

Mawussi Zounon will give a talk about PLASMA and the NAG Library.

### Wednesday March 13, 2019

Xuelei Lin from Hong Kong Baptist University

Title: Crank-Nicolson ADI method for space-fractional diffusion equations with non-separable coefficients

Abstract: Alternating direction implicit (ADI) scheme is a popular and efficient solver for linear systems arising from discretization of high-dimension fractional PDEs. However, ADI schemes developed in previous works requires strong assumptions, such as separable coefficients, or even constant coefficients. In this talk, I will introduce our newly developed theory for Crank-Nicolson ADI, which does not require separable-coefficients assumptions. Also, an optimal preconditioning technique is applied to the one-dimensional problems arising from ADI scheme, for which the condition number of the preconditioned matrices are proven to be independent of discretization step-sizes.

### Wednesday March 6, 2019

Chris Armstrong from Arm

Title: Arm Performance Libraries FFT development

Abstract: In this talk I will give a quick overview of Arm Performance Libraries before describing the work we have undertaken to improve the performance of our Fast Fourier Transform (FFT) functions. I will outline the algorithms we use and our results to date.

### Wednesday January 30, 2019

Pierre Blanchard on “Yet Another Fast And Accurate Summation Algorithm”.

### Wednesday January 23, 2019

Sven Hammarling on “Machines for the Solution of Linear Equations”. Notes, Slides and References.

### Tuesday December 11, 2018

Massimiliano Fasi on “Efficient and Accurate evaluation of polynomials of matrices”. Notes and Slides.

### Tuesday December 4, 2018

Theo Mary on “A New Approach to Rounding Error Analysis”. Paper and Slides.

### Tuesday November 20, 2018

Lijing Lin on “Phenotyping immune responses in asthma and respiratory infections using clustering techniques”. An abstract for the talk is available here.

### Tuesday November 13, 2018

Srikara Pranesh on “Squeezing a Matrix Into Half Precision, with an Application to Solving Linear Systems”.

### Tuesday November 6, 2018

Elisa Riccietti on “High-order multilevel optimization strategies and their application to the training of artificial neural networks”. Abstract for the talk is available here.

### Tuesday October 30, 2018

Gain Maria Negri Porzio on “The contour integral approach for the nonlinear eigenvalue problem”.

### Tuesday October 23, 2018

Nick Higham on “The adjugate matrix”. From the meeting: Notes.

### Tuesday October 16, 2018

Tom McSweeney on ”Task scheduling in high-performance computing”. From the meeting: Slides, Notes.

### Tuesday October 9, 2018

Nick Higham on ”Optimizing the Wilson Matrix”. From the meeting: Notes.

Here is the group photo from the meeting (hires version).

### Tuesday October 2, 2018

### Tuesday September 25, 2018

Introductions, new website, and plans for the academic year, including conferences. From the meeting: Notes.