3rd CEEC Community Workshop - Vistle Part II: Hands-On Workshop for 3D Data Visualization
2025-05-21 15:00 - 17:00 (Europe/Paris) | HLRS University of Stuttgart, Nobelstraße 19, Stuttgart, 70569, Germany
Join us for Part II of our Vistle series on site in Stuttgart!
In this hands-on two-hour workshop, you will get to know Vistle, a powerful open-source visualization tool, and learn how to create compelling 3D representations of scientific datasets, both in desktop as well as Virtual Reality environments. After an introduction to the software and its key features, you will have the opportunity to apply your knowledge and create your own visualization.
The workshop will be held on-site in Stuttgart at HLRS, the High-Performance Computing Center Stuttgart. For information on reaching HLRS and where to stay, please see the HLRS contact us page.
Check-in is available starting at 14:00 CEST including a tour of the HLRS CAVE. The workshop then begins at 15:00 CEST.
For any other questions about the workshop, please contact us!

Mixed-Precision and Energy-Efficient Computations
2025-06-10 15:00 - 2025-06-12 16:00
As supercomputers get bigger, they become both more capable of solving complex problems and consuming enormous amounts of energy. To ensure their sustainability, we must start focusing on reducing energy-to-solution at least as much as we focus on reducing time-to-solution. One of the ways CEEC is working on this is using mixed precision.
Join Yanxiang Chen at ISC in the Foyer D-G – on the 2nd floor to learn about our latest work reducing precision and energy consumption without compromising accuracy.

CEEC at ISC25
2025-06-11 13:00 - 13:20
Join our own Niclas Jansson at the Euro HPC JU booth for a presentation on our project and progress so far!

RESEARCH POSTER PITCH with Yanxiang Chen
2025-06-11 13:30 - 14:15
After listening to Niclas Jansson present our project at the EuroHPC JU booth at 1pm, strole over to Hall E to hear from our own Yanxiang Chen.
If you want the chance to ask questions about how we’re using mixed precision to drive energy-to-solution down without compromising accuracy, make sure to stop by the research poster pitch !
Yanxiang will present and answer questions about his poster Mixed-Precision and Energy-Efficient Computations.

Fully-resolved LBM-DEM simulations of piping erosion during a suction bucket installation
2025-07-01 00:00 - 2025-07-05 00:00 | Arcrea HIMEJI, 143-2, Kamiyacho, Himeji-City, Hyogo, 670-0836, Japan
Join our Samuel kemmler in Himeji, Japan for the 10th International Conference on Discrete Element Methods (DEM10) this summer!
Suction bucket foundations are a cost-efficient and environmentally sustainable solution to install offshore wind turbines, achieved through the application of growing suction pressure inside the bucket until its full embedment into the seabed. A key challenge for the installation process is the occurrence of piping erosion, a phenomenon where fluidization of particles beneath the bucket wall tip causes a drop in suction pressure, potentially leading to installation failure. Despite its significance, the complex physical mechanisms driving piping erosion remain insufficiently understood. To address this knowledge gap, a three-dimensional, fully-resolved coupled LBM-DEM simulation is employed to conduct an in-depth analysis of piping erosion, aiming to identify key influencing parameters, thus enhancing understanding and optimizing the installation process. The simulation of physically relevant problem sizes – comprising hundreds of thousands of grains – is equivalent to computational intensities which demand for extensive computational resources. Results from simulations executed on hundreds of GPUs on the LUMI supercomputer are presented, illustrating the method’s capability to tackle this complex challenge.

FLEXI: Scale-resolving simulations of compressible turbulence on modern HPC systems
2025-08-27 16:20 - 16:40 | TUD Dresden University of Technology Barkhausen-Bau (BAR), Georg-Schumann-Str. 13 , Dresden, 01069, Germany
Join our own Anna Schwarz for the WHPC Europa invited session discussing our latest work preparing FLEXI for exascale and GPU-based systems.
Abstract
The application of scale-resolving simulations such as LES and DNS remains challenging in numerous engineering applications due to the substantial computational demands and the limited available computational resources. It was thoroughly demonstrated in the last decade that high-order numerical methods show significant advantages in terms of computational cost required to achieve a given accuracy for DNS and LES and that they can be implemented efficiently on traditional CPU-based system architectures. However, the improvements in performance for CPU-based systems has slowed down significantly over the last years. Consequently, more specialised architectures, such as GPUs, have become increasingly popular in the last decade. These architectures still promise considerable performance improvements per generation and thus allow more complex flow cases to be tackled, while also yielding better performance per invested amount of energy. However, CPU codes cannot be easily run on GPU hardware, since they exhibit a distinctly different architecture and require different programming languages. In this talk it is demonstrated how existing codebases can be translated efficiently to GPU hardware, both in terms of implementation effort and computational performance. For this, the unstructured DG code FLEXI~cite{Krais2019,Kempf2024} is utilized as an example. Finally, it is shown that FLEXI is capable of tackling challenging large-scale problems with complex geometries on modern HPC systems.

Exploring Flow Fields at Scale: GPU-Accelerated Scientific Visualization for Exascale CFD
2025-08-27 16:40 - 17:00 | TUD Dresden University of Technology Barkhausen-Bau (BAR), Georg-Schumann-Str. 13 , Dresden, 01069, Germany
Join our own Susanne Malheiros at the WHPC Europa Invited Session to hear about our latest work on Vistle.
Abstract:
This talk presents the ongoing efforts to port Vistle – a software for creating immersive extended reality visualizations of scientific data – to the GPU by integrating the portable visualization toolkit Viskores. The approach is illustrated by sample computational fluid dynamics (CFD) visualizations of the light-house cases from the Center of Excellence in Exascale CFD (CEEC) project.

Introduction to the DLB Library and Measuring GPU performance
2025-09-17 15:00 - 16:00 | Online
The Dynamic Load Balancing library is a runtime library that offers different capabilities to HPC users. It consists of three different modules that work collaboratively and independently:

Lend When Idle (LeWI): Offers a transparent load balancing mechanism for hybrid applications (MPI + OpenMP)
Tracking Application Life Performance (TALP): Collects performance metrics at runtime, offering a transparent and lightweight tool to measure the parallel and computational efficiency of your code. Metrics can be collected during runtime, offering the possibility of dynamic adaptation.
Dynamic Resource Ownership Management: Provides a mechanism to change the amount of computational resources used by the different processes at runtime without stopping the application.

In this webinar we’ll provide an overview of the DLB library and each one of its modules. For each module we’ll share its main features, how to use it, and some success stories. We’ll put special focus on the TALP module and its recent extension to provide GPU metrics when getting performance measurements.

Mixed-Precision and Energy-Efficient Computations
2025-10-09 12:10 - 14:30
If you’re at the Workshop on Approximate Computing in Numerical Linear Algebra in Paris this week, don’t miss Yanxiang Chen’s lunch poster talk on mixed precision and energy efficient computations!
Abstract: High Performance Computing has traditionally focused on optimizing between memory usage, arithmetic intensity, parallelism, and communication costs. However, as simulations grow, energy consumption has surged, presenting significant sustainability challenges for large-scale computing infrastructures. Addressing these challenges requires innovative strategies that enhance energy efficiency without compromising computational accuracy or performance.
We present a systematic methodology for reducing the energy footprint of large-scale simulations via mixed-precision computing, without compromising accuracy or performance. Our approach combines performance profiling with numerical sensitivity analysis to identify precision-insensitive code regions, select promising candidates, and gradually convert them to lower precision. Applied to representative high-performance computing kernels, this strategy yields up to 40% speedup and 47% energy savings in an implicit Poisson solver, and roughly 30% gains in both execution time and energy consumption in explicit solvers, all while preserving double-precision level accuracy. These results demonstrate that our methodology provides a versatile and effective lever for enhancing the sustainability of HPC applications.

Mixed-Precision Strategies in Spectral Element Codes: Accuracy-Aware Approximation for Energy-Efficient Simulations
2025-10-09 15:50 - 16:10
If you’re at the Workshop on Approximate Computing in Numerical Linear Algebra in Paris this week, chec out Roman Iakymchuk’s talk on mixed-precision strategies in spectral element codes on Thursday!
Abstract: Approximate computing via mixed precision arithmetic offers a promising path to energy-efficient high-performance computing. However, identifying where and how to apply reduced precision without compromising solution accuracy remains a key challenge in scientific simulations. In this talk, we present a comprehensive methodology for enabling mixed-precision in spectral element codes using floating-point analysis tools, roofline modeling, and empirical verification. We apply our strategy to Nekbone and Neko—two fluid dynamics solvers—by combining reduced-precision iterative solvers with double-precision critical operations such as dot products and global communications. Our method is supported by Verificarlo’s Monte Carlo arithmetic and precision emulation, which help detect numerically stable kernels for approximation. The resulting mixed-precision versions deliver up to 2.38x faster time-to-solution and 2.8× lower energy-to-solution, while retaining double-precision-level accuracy. This work highlights a practical, accuracy-aware approach to integrating approximation into large-scale legacy applications, making them fit for future exascale platforms.

Extreme-Scale High-Fidelity Computational Fluid Dynamics with Neko
2025-10-22 14:00 - 15:00 | Online
Neko is a portable framework for high-order spectral element-based simulations, mainly focusing on incompressible/compressible flow. The framework is written in a modern object-oriented approach and supports various hardware backends, ranging across general-purpose processors, accelerators, and vector processors. Neko has demonstrated excellent performance and scalability across various hardware architectures and was nominated as a finalist for the ACM Gordon Bell prize in 2023.
In this webinar, we will provide an introduction to Neko and its capabilities, from installation to creating and running simulations. Special focus will also be on the major changes in terms of features and functionalities, user interaction, and improvements made in the upcoming release of Neko v1.0. By the end of the webinar, attendees will have a basis as well as references and materials to start working with Neko on their own time.

Exploring CI/CD Tools and Workflows for Research and HPC Software Projects
2025-11-26 14:00 - 15:00 | Online
Continuous Integration and Continuous Deployment (CI/CD) are essential for sustainable and reproducible software development, yet many projects still lack a structured workflow.
This webinar provides a beginner-friendly introduction to CI/CD with a focus on EuroHPC. We will explore why CI/CD matters, review a selection of tools commonly used or even developed within European projects, and discuss their strengths, limitations, and typical use cases.
The goal is to help developers new to CI/CD understand available options and how to choose tools that fit their needs. A short example from the waLBerla project will illustrate how such workflows can be applied in practice.

Performance Portability for Fortran CFD Software with GALÆXI
2025-12-09 14:00 - 15:00 | Online
With GPU acceleration now ubiquitous in HPC, there is more pressure than ever to port existing simulation software to leverage the new hardware. There are many GPU programming models available, but they often have limited, or completely lack, support for Fortran. This leads owners of existing Fortran scientific codes to struggle with porting their software to multiple computing architectures. One option is to turn to C++ to achieve the greatest performance portability.
This webinar is a guide for the process of taking a Fortran CFD code and porting it to GPUs using CUDA/HIP C++. The basics of GPU hardware and programming will be covered, to serve as a rough guide for adapting algorithms and data structures. The high-order discontinuous Galerkin spectral element CFD code GALÆXI is then presented. The important design questions and porting requirements in GALÆXI are discussed, which researchers must answer and understand to effectively port their own Fortran codes with CUDA/HIP C++.

Task-decomposed Overlapped Preconditioner for Sustained Strong Scalability on Accelerated Exascale Systems
2026-01-28 11:30 - 12:00
Join Niclas Jannson in Osaka, Japan at SCA/HPCAsia2026 for his talk on “Task-decomposed Overlapped Preconditioner for Sustained Strong Scalability on Accelerated Exascale Systems.”

A Matrix-Free Algebraic hp-Multigrid Method for Computational Fluid Dynamics Applications
2026-01-28 12:00 - 12:30
After the talk on preconditioners in Osaka, Japan at SCA/HPCAsia2026 , stick with Niclas Jannson for his next talk on “A Matrix-Free Algebraic hp-Multigrid Method for Computational Fluid Dynamics Application., a best paper finalist. “

CEEC at the 1st Stuttgart Research Software Day
2026-03-02 16:45 - 18:30
What is research software and why does it matter? These questions are the point of the first ever Research Software Day at the University of Stuttgart. Come learn about the CEEC codes FLEXI/GALAXI during the poster session and stay to learn about what else is being developed on campus.

FAIR-FLEXI - A Trustworthy CFD Code for Simulation and Training
2026-03-03 16:10 - 16:30
Engineering and science disciplines, especially computational fluid dynamics (CFD) generate massive amounts of research data, but they can only become knowledge if they can be shared and explored through data analytics and AI. This, in turn, requires a FAIR (findable, accessible, interoperable, reusable) infrastructure. For complex research software, however, FAIR goes far beyond being open-source: reproducibility is hindered by hidden expertise such as user-defined parameters, compile options, hardware constraints, and third-party dependencies.
This talk outlines the design, implementation, and lessons learned from FAIR-FLEXI. We discuss how comprehensive provenance capture, portable environments, and interactive notebooks turn CFD workflows into trustworthy, reproducible research assets.

GALAEXI: An Architecture-Agnostic GPU-Acceleration Approach for Legacy Fortran Software
2026-03-03 18:25 - 18:50
Join Spencer Starr at the Society for Industrial and Applied Mathematics (SIAM)Processing for Scientific Computing (PP26)confrence in Berlin for his talk on “GALAEXI: An Architecture-Agnostic GPU-Acceleration Approach for Legacy Fortran Software”
GALAEXI is a high-order discontinuous Galerkin spectral element method (DGSEM) computational fluid dynamics (CFD) code used for the study of compressible, turbulent flows. It is the device-accelerated version of an existing Fortran-based, CPU-only CFD framework. In this talk, the chosen strategy for porting the Fortran-based compute kernels in GALAEXI to CUDA/HIP C++ is covered. Included are discussions on managing device memory, retaining support for CPU computations, strategies for writing and testing kernels and how to handle GPU-to-GPU MPI communication. Specific emphasis is placed on how the strategies covered can be abstracted in an architecture-agnostic way to allow the greatest degree of portability. The information presented will then be distilled into advice for those seeking to perform a similar porting effort.

Flagship scientific applications on a European RISC-V long-vector accelerator: Lessons learned
2026-04-29 14:00 - 15:00 | Online
As Europe accelerates its efforts in chip sovereignty, scientific applications need to be ported to and evaluated on emerging prototypes, assessing their performance as well as the technology readiness of the new hardware platforms. In this talk, we will share the experiences and lessons learned when porting applications from CEEC and other Centers of Excellence to the long-vector RISC-V accelerators from the EPI and EUPILOT projects across different domains and applications.
Attendees will learn code optimization techniques, common performance pitfalls, and evaluation methods for long-vector architectures, which they can apply to their own applications and code bases in order to improve performance on these novel hardware platforms.

Enabling mixed-precision with VerifiCarlo: Sharing CEEC experience
2026-05-27 15:00 - 16:00
Join our own Roman Iakymchuk, Umeå University on behalf of CEEC, and Pablo de Oliveira Castro, Université Paris-Saclay UVSQ, for a 2nd look at VerifiCarlo!
Driven by the increasing need to reduce the energy consumption of computing centers and simulations, scientists have begun revising applications, algorithms, and their underlying working/storage precision not just for performance but also for energy efficiency. The goal is to make computational costs sustainable while adhering to the lagom principle—using precision that is “just right” to balance accuracy with efficiency.
However, before lowering precision, one must ensure that the simulation is numerically correct. Verificarlo is an open-source framework designed to verify and optimize numerical accuracy in complex programs. Built on the LLVM infrastructure, it provides various floating-point backends to simulate the effects of numerical errors and lower precision. By leveraging alternative floating-point models, such as Stochastic Rounding, Verificarlo pinpoints numerical bugs in simulation codes. A probabilistic definition of the number of significant digits allows us to estimate computational accuracy accurately.
Through its variable precision backend, Verificarlo enables one to explore the trade-offs between precision and performance by simulating lower precisions in software. It identifies specific code regions that benefit from reduced floating-point formats without sacrificing numerical correctness. This approach has been successfully applied in high-performance computing (HPC) domains such as neuroimaging pipelines, DFT quantum mechanical modeling, structural simulations, and now CFD.
In this webinar, we will introduce Verificarlo, showcase its backends for numerical bug detection and mixed-precision analysis, and present a success story highlighting the road from analysis of codes with Verificarlo to reliable mixed-precision codes.

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