Overview

We are organizing a workshop for everyone already using HyTeG and TerraNeo and those interested to try it out:

• Dates: Monday & Tuesday, 5th & 6th of May 2025, 10:00 - 17:00
• Venue: Leibniz Supercomputing Center, Garching (near Munich)
• Costs: The workshop itself is free of charge
• Programme: see below

Registration

As number of places is limited, you need to register for the workshop.

Schedule and Abstracts

Day 1 (Monday, May 05, 2025)

Time	Title	Speaker
10:00	Welcome
10:30	HyTeG: How to solve linear systems with trillions of unknowns	Nils Kohl (LMU)
11:30	Lunch
12:30	Hands-on HyTeG	Marcus Mohr (LMU)
13:30	Coffee break
14:00	Code generation: From a mathematical description to a fast implementation without the pain	Daniel Bauer (FAU)
15:00	Discussion
16:00	LRZ tour: visualization infrastructure
17:00	Departure

Day 2 (Tuesday, May 06, 2025)

Time	Title	Speaker
10:00	Arrival
10:30	Solving discrete Stokes problems	Fabian Böhm (FAU)
11:30	Lunch
12:30	Hands-on TerraNeo	Ponsuganth Ilangovan (LMU)
13:30	Coffee Break
14:00	HPC system introduction and usage	Arjun Parab (LRZ)
15:00	Discussions
17:00	Departure

Abstracts

Day 01

HyTeG: How to solve linear systems with trillions of unknowns

10:30 - Speaker: Nils Kohl (LMU)

This overview talk introduces the fundamental parallel algorithms and data structures of the HyTeG finite element framework. HyTeG (Hybrid Tetrahedral Grids) has been built to approximate partial differential equations at the extreme scale, with a strong focus on matrix-free geometric multigrid methods. We will look at the basic building blocks that enable the solution of linear systems with trillions of unknowns on state-of-the-art supercomputers, give a summary of the most relevant features, and show example simulation results.

Hands-on HyTeG

11:30 - Speaker: Marcus Mohr (LMU)

In this part of the workshop participants get the chance to play with HyTeG themselves. Together, we will go through the standard steps for setting up a simulation. This includes all aspects starting from cloning the project, configuring and building it, up to setting up your own "app" on top of the framework.

Participants will learn how to import or generate a mesh, select finite-element spaces for their functions, perform interpolation of expressions, apply operators to functions, solve linear systems and export data for visualisation. In the end each one should have their own FE solver for a standard Poisson or maybe even a Stokes problem.

Code generation: From a mathematical description to a fast implementation without the pain

14:00 - Speaker: Daniel Bauer (FAU)

In a matrix-free finite element code, matrix-vector products are typically the most performance-critical ingredient. However, developing, optimizing, and maintaining highly efficient kernels becomes tedious quickly, if a wide variety of PDEs, discretizations, optimization techniques, and hardware architectures shall be supported. This tutorial presents HOG, HyTeG's operator generator, the concepts behind it, and teaches how to generate an efficient kernel from a mathematical description.

Day 02

Solving discrete Stokes problems

10:30 - Speaker: Fabian Böhm (FAU)

The Stokes partial differential equation (PDE) models many geodynamic phenomena, such as mantle convection. For its numerical solution, we discretize the PDE using finite elements. The resulting linear system has saddle-point properties and requires tailored linear solvers to solve it efficiently. This tutorial explains the preconditioners and linear solvers commonly used to solve discrete Stokes problems. We put particular emphasis on multigrid, which provides a crucial property: grid-independent convergence.

Hands-on TerraNeo

12:30 - Speaker: Ponsuganth Ilangovan

Here is where each pieces of the puzzle comes together into the final application. TerraNeo is the mantle convection framework developed on top of HyTeG, while making use of the multigrid solvers that were developed for the Stokes system with strongly varying viscosity at globally fine resolutions. In this session, first the formulations of the coupled Stokes-Transport system with the approximations needed such as the TALA (Truncated Anelastic Liquid Approximation) and handling advection with MMOC (Method of Modified Characteristics) will be discussed. Then the techniques that are used to simplify the Stokes system in the context of HPC will be explained with a final demonstration of TerraNeo for a successful Geophysical application.

HPC system introduction and usage

14:00 - Speaker: Arjun Parab

This talk presents an overview of the Leibniz Supercomputing Center, its service portfolio, research areas, and system infrastructure along with a brief introduction to their usage.