# Sixth deal.II Users and Developers Workshop

23-27 July 2018
SISSA Main Building
Europe/Rome timezone
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## Contribution List

Displaying 21 contributions out of 21
Type: Contributed talks Session: Contributed talks
Track: Users' track
In this talk I will recall some basic notions of augmented and deflated Krylov space methods for the iterative solution of linear systems. Then I will discuss a few strategies to apply these techniques to the solution of linear systems coming from nonlinear scalar convection-diffusion equations. A simple back-of-the-envelope analysis allows to argue that in some cases it may be convenient to exp ... More
Presented by Giuseppe PITTON on 23 Jul 2018 at 11:00
Type: Keynote presentations Session: Keynotes
Track: Developers' track
Traditional solution approaches for problems in quantum mechanics scale as $\mathcal O(N^3)$, where $N$ is the number of electrons. Various methods have been proposed to address this issue and obtain linear scaling $\mathcal O(N)$. One promising formulation is the direct minimization of energy. Such methods take advantage of physical localization of the solution, namely that the solution can be so ... More
Presented by Denis DAVYDOV on 26 Jul 2018 at 09:00
Type: Keynote presentations Session: Keynotes
Track: Developers' track
Version 9.0.0 of the deal.II library offers many new features and interfaces with several new external libraries. In this talk I will provide an overview of some of the new features that I have contributed in adding to the library, including (in no particular order) - Improved support for curved geometries - Non-standard quadrature rules - Improved support for user-defined run-time ... More
Presented by Prof. Luca HELTAI on 27 Jul 2018 at 09:00
Type: Keynote presentations Session: Keynotes
Track: Developers' track
There are several different ways of describing bilinear forms in deal.II. All of these require to describe the assembly loop inside the program. This talk discusses an approach for providing the assembly operator from the outside using a domain-specific language. In particular, this easily allows changing the backend used in the end. CFL also provides the possibility to generate the Newton li ... More
Presented by Daniel ARNDT on 24 Jul 2018 at 09:45
Track: Developers' track
Some conclusions and some plans for future developments and opportunities. In particular: - How to attract funds to deal.II - How to attract new users - Open discussions on the best platforms for Forums/Discussions/Mailinglists - Anything else
Presented by Prof. Wolfgang BANGERTH, Timo HEISTER, Prof. Luca HELTAI on 27 Jul 2018 at 12:30
Type: Contributed talks Session: Contributed talks
Track: Users' track
Given the context of distributed parallelism, the purpose of this contribution is to consider a solution procedure to the classical Stefan phase change problem, an example of a free boundary problem. In the Stefan problem, the interface between water and ice moves through a domain as the ice melts due to a heat source. As an example of an interface problem, we choose to apply the level set method ... More
Presented by Mr. Sean MCGOVERN on 23 Jul 2018 at 11:20
Type: Invited talks Session: Keynotes
Track: Users' track
Many modern 3D modelling tools offer the possibility of creating complex geometries in a very straightforward way (what is usually called creative freedom). Such softwares are extensively used in computer graphics (video-gaming, animation studios) and they are able to produce smooth surfaces exploiting the subdivision surface modelling which was derived by Edwin Catmull and Jim Clark in 1978 as a ... More
Presented by Mr. Nicola GIULIANI on 25 Jul 2018 at 09:45
Type: Contributed talks Session: Contributed talks
Track: Users' track
Cosmic ray propagation in fluid approach can be described as a PDE system, which lives in 6D spatial-spectral space. In our project, we attempt to build up a solver for such a system, by combining independent triangulation in two domains (spatial and spectral). In this talk, I will present why and how we build this framework with Kronecker product.
Presented by Jiaxin WANG on 23 Jul 2018 at 11:40
Type: Invited talks Session: Contributed talks
Track: Users' track
The goal of the ExaDG project is to provide efficient finite element solvers relying on deal.II's MatrixFree framework based on higher order DG methods. However, the matrix-free operators restrict the choice of preconditioners. A powerful tool is offered by a geometric multigrid algorithm having a favorable linear complexity. The quality of multigrid preconditioners is crucially dependent on t ... More
Presented by Julius WITTE on 25 Jul 2018 at 11:40
Type: Contributed talks Session: Contributed talks
Track: Users' track
It has been recently shown that a Diffuse Interface model is able to fully describe the dynamics of multiphase flows. In particular, the possibility of deriving a set of equations addressing the dynamic of the entire domain of simulation, makes it ideal to describe phenomena such as vapor bubble dynamics in a surrounding liquid. The model is able to capture surface tension effects, phase changes ( ... More
Presented by Dario ABBONDANZA on 24 Jul 2018 at 11:00
Type: Keynote presentations Session: Keynotes
Track: Developers' track
In recent years there has been a notable growth in research among fields involving coupled media, and in multi-physics problems in general. As the complexity of the physics describing the material loading and response increases, so does the time cost and sophistication of the computational tools used to analyse these problems both in the academic and industrial settings. Associated with this are f ... More
Presented by Dr. Jean-Paul PELTERET on 24 Jul 2018 at 09:00
Type: Contributed talks Session: Contributed talks
Track: Users' track
The mechanical response of magnetorheological composites is highly affected by an applied magnetic field. Since a generally valid constitutive law does not exist for such heterogeneous materials, multiscale techniques like computational homogenisation are commonly used to approximate effective macroscopic properties. In our approach the macroscopic quantities at a material point of a magnetorheolo ... More
Presented by Mr. Benjamin BRANDS on 24 Jul 2018 at 11:20
Type: Contributed talks Session: Contributed talks
Track: Users' track
The goal of my work is to develop robust scalable solver for linear system arising from finite element discretization of Stokes problem with strongly variable viscosity. Such linear systems appear in fluid-structure problems. Symmetric positive define problems with discontinuous coefficient can be solved effectively by multigrid preconditioned Krylov subspace methods. Here we extend this idea ... More
Presented by Michal WICHROWSKI on 25 Jul 2018 at 11:20
Type: Contributed talks Session: Contributed talks
Track: Users' track
I am beginning this talk with a quick recall of the general difficulties faced when using multiple grids on a distributed memory setting and some possible solutions. As a model problem I am presenting briefly the Lagrange-multiplier method of step-60, where a harmonic equation with values prescribed at the boundary and on a sub-domain is solved, with a particular focus on the coupling matrix used ... More
Presented by Mr. Giovanni ALZETTA on 25 Jul 2018 at 11:00
Type: Contributed talks Session: Contributed talks
Track: Users' track
During the last 8 years the mathLab laboratory at SISSA has analysed the swimming mechanisms of micro-organisms (unicellular beings as protists, algae or bacteria) both from a theoretical and an experimental point view. In this work we present a way to derive an accurate and reliable numerical setting for the resolution of general swimming mechanism. Such a framework can be seen as a numerical mic ... More
Presented by Dr. Nicola GIULIANI on 24 Jul 2018 at 11:40
Type: Invited talks Session: Keynotes
Track: Users' track
In this talk, we propose a new nonconforming finite element algorithm to approximate a linear problem involving the integral fractional Laplacian. The method is based on the Dunford-Taylor integral representation of the bilinear form corresponding to the variational formulation. We obtain the approximated solution using the deal.II finite element library with a non-uniform mesh setting. Finally, a ... More
Presented by Dr. Wenyu LEI on 26 Jul 2018 at 09:45
Type: Keynote presentations Session: Keynotes
Track: Developers' track
Multigrid methods are the only known approach to efficiently solve large linear systems for solving PDEs by having runtime cost proportional to the number of unknowns. Algebraic multigrid methods construct a hierarchy of problems from the system matrix, while geometric multigrid methods use the mesh hierarchy and system matrices from each level of this hierarchy. While algebraic multigrid m ... More
Presented by Timo HEISTER on 23 Jul 2018 at 09:45
Type: Keynote presentations Session: Keynotes
Track: Developers' track
GPUs are extensively used in supercomputers both in Europe with Piz Daint and in the United States with Titan, Sierra, and Summit. The main reason is that they offer great floating points performance for a given power envelope. GPUs are also the de facto standard architectue for neural networks whose usage has been increasing quite rapidly in the last few years. It is therefore very advantageous i ... More
Presented by Bruno TURCKSIN on 25 Jul 2018 at 09:00
Type: Invited talks Session: Keynotes
Track: Developers' track
deal.II is now 20 years old. I'll give a brief overview of how it started, how it has developed, and where I see it going in the future. This includes both the technical side and, in particular, the social side: deal.II is not just a software project, but also a community of developers and users.
Presented by Prof. Wolfgang BANGERTH on 23 Jul 2018 at 09:00
Type: Contributed talks Session: Contributed talks
Track: Users' track
To exploit the automated mesh generation and adaptive refinement capabilities offered by deal.II, the user must provide its program with a suitable description of the domain geometry. In particular, it is fundamental that the geometries of boundary and internal surfaces are available to the triangulation so that the nodes generated across each mesh refinement are placed onto such surfaces, in a wa ... More
Presented by Dr. Andrea MOLA
Type: Contributed talks Session: Contributed talks
Track: Users' track
To exploit the automated mesh generation and adaptive refinement capabilities offered by deal.II, the user must provide its program with a suitable description of the domain geometry. In particular, it is fundamental that the geometries of boundary and internal surfaces are available to the triangulation so that the nodes generated across each mesh refinement are placed onto such surfaces, in a wa ... More
Presented by Dr. Andrea MOLA on 26 Jul 2018 at 11:00