A continuous benchmarking pipeline for performance engineering on different architectures for the waLBerla framework
2024-09-03 16:50 - 17:10 (Europe/Paris) | Universitätsclub Bonn e.V., Konviktstr.9, Bonn, 53113, Germany
Come listen to our own Kajol Kulkarni presenting in mini-symposium 4 at parCFD on our work with benchmarking of waLBerla.

Keynote Lecture at parCFD
2024-09-03 18:15 - 19:00 | Universitätsclub Bonn e.V., Konviktstr.9, Bonn, 53113, Germany
Join our own Niclas Jansson for his keynote lecture as an invited speaker at the 35th Parallel CFD International Conference 2024 in Bonn, Germany.

'Enabling mixed-precision with the help of tools: A Nekbone case study' at PPAM24
2024-09-09 12:05 - 12:25 | Ostrava, Czechia, Ostrava, Czech Republic
If you’re going to PPAM24 September 8 – 11 in Ostrava, Czechia, make sure to check out the talk by Yanxiang Chen from our partner UMU on their progress implementing and optimizing mixed precision in Nekbone toward its integration in Neko and NekRS. The accompanying paper is also available as a pre-print online: https://arxiv.org/pdf/2405.11065

Introduction to Computational Fluid Dynamics
2024-09-16 - 2024-09-20 | HLRS University of Stuttgart, Nobelstraße 19, Stuttgart, 70569, Germany
Join our Anna Schwarz as one of the instructors for the reoccuring “Introduction to Computational Fluid Dynamics” course organized by HLRS, IAG (University of Stuttgart) and the
Institute of Software Methods for Product Virtualisation (DLR).

FLEXI/GALÆXI: Open-Source Solver for Multiscale Flows
2024-10-30 11:00 - 12:00
Join us for the 11th CASTIEL Code of the Month to learn about FLEXI/GALÆXI!
In the field of computational fluid dynamics (CFD), high-order methods have reached a certain level of maturity for the solution of unsteady multiscale problems, of which turbulence is a prime example. For these types of problems, high-order schemes have proven to be efficient alternatives to more traditional numerical schemes. Among the high-order discretization variants, the discontinuous Galerkin method offers a collection of features which increased its popularity. In order to take full advantage of the potential benefits of these methods, all steps in the simulation chain, from pre- to post-processing, must be designed and executed with high-order in mind.
In this talk, we will present the open-source CFD frameworks FLEXI/GALÆXI, which are continuously developed by the Numerics Research Group of Prof. Andrea Beck at the Institute of Aerodynamics and Gas Dynamics at the University of Stuttgart. Both solvers provide a high-order consistent simulation tool chain for solving the compressible Navier–Stokes equations in a highly efficient, accurate and robust manner in a high performance computing setting either on CPU-based systems (FLEXI) or GPUaccelerated clusters (GALÆXI). The talk commences with a description of the numerical algorithms and implementation details, accompanied by an outline of the features and capabilities of all parts of the framework. In addition to these technical details, we also discuss the significant issues of code stability, reproducibility and user-friendliness. The advantages gained by developing an open-source framework are addressed, with a particular focus on usability for the open-source community. We conclude with application examples that demonstrate the wide range of use cases and the extensibility of FLEXI, as well as an overview of current and future developments.
Registration:
https://forms.office.com/e/P4Kr9xweRN

Introduction to the DLB Library
2024-11-13 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 tutorial we will provide an overview of the DLB library and each one of its modules. For each module we will share its main features, how to use it, and some success stories.

Call for Abstracts! High-fidelity CFD with application in ship hydrodynamics
2024-12-15 00:00 - 23:59
Submit your abstract to our invited session at Marine 2025!!
The session titled “High-fidelity CFD with application in ship hydrodynamics” is seeking submissions by December 15th, 2024. Full details and guidelines for submission are available in the proposal .
You can also check out the invited session’s page on the conference website.

Programming complex workflows with PyCOMPSs
2024-12-16 11:00 - 12:00 | Online
Programming large-scale systems poses several challenges to scientific application developers. Systems are growing in complexity, and concurrency is not the only difficulty that programmers face. They also contend with the distribution of memory spaces, complex architectures, new storage technology, etc. Task-based programming models have proven to be a good alternative to traditional programming models for HPC. PyCOMPSs is a pioneering approach to task-based programming in Python that enables codes to be executed in distributed computing platforms. In particular, PyCOMPSs supports different types of tasks, such as parallel simulations (MPI), artificial intelligence, or data analytics. This webinar will give an overview of PyCOMPSs illustrated with examples in development at BSC that include CFD simulations with AI training or real-time visualization in the same workflow.

Scientific Visualization for Exascale Simulations
2025-01-20 12:30 - 12:50 | Room 9
Join our own Susanne Malheiros for her presentation “Scientific Visualization for Exascale Simulations” at HiPEAC25!
Part of the workshop “From petascale to exascale and beyond: the Centres of Excellence challenge”, Susanne will present her work on visualizing exascale CFD and multi-physics simulations like our Localized Erosion of Wind Turbine foundations lighthouse case.

Exploring quantum computing in CoEs
2025-01-22 10:00 - 10:20 | Room 9
Join our Pratibha Raghupati to learn about her experience exploring the potential of quantum in the context of work being done by the European HPC Centers of Excellence!
Part of the workshop “Tackling software exascale challenges: the Centres of Excellence in High Performance Computing perspective”, she will present the potential impact of quantum in the context of exascale CFD simulations we’re working on in CEEC.

GALEXI: Scale-resolving simulations of compressible turbulence on GPU-accelerated systems
2025-01-22 14:00 - 14:20 | Room 9
Joine our Anna Schwarz for her talk “GALEXI: Scale-resolving simulations of compressible turbulence on GPU-accelerated systems”, part of the workshop “Tackling Software Exascale Challenges: the Centres of Excellence in High-Performance Computing Perspective”. She will present GALEXI, the GPU version of FLEXI, and the grogress she’s made in CEEC preparing these codes for exascale CFD simulations.

Vistle Part I: An Introduction to Immersive Visualizations of Large-Scale Scientific Data
2025-01-29 10:00 - 11:00
Save the date for our next webinar!
This one-hour webinar introduces the visualization tool Vistle, which is used to create augmented reality/virtual reality visualizations of large-scale scientific datasets. It presents Vistle’s remote rendering functionality and how Vistle is being ported to GPUs as part of the CEEC project to enable visualization for exascale datasets.
Agenda

Introducing Vistle

Examples of Immersive Visualizations
The Visualization Pipeline

Preparing Vistle for the Exascale Era

Hybrid Remote Rendering
Adding GPU support with VTK-m

Neko: A Modern, Portable, and Scalable Framework for Extreme-Scale Computational Fluid Dynamics
2025-03-03 10:45 - 11:00
Join our own Niclas Jansson at the SIAM Conference on Computational Science and Engineering (CSE25) in Fort Worth, Texas, for his talk “Neko: A Modern, Portable, and Scalable Framework for Extreme-Scale Computational Fluid Dynamics” in the mini-symposium MS19: Performance Benchmarking of Scientific Libraries and Applications.
Recent trends and advancements in utilizing more diverse and heterogeneous hardware in High-Performance Computing (HPC) are challenging scientific software developers in their pursuit of efficient numerical methods with sustained performance across a diverse set of platforms. As a result, researchers are bing forced to refactor their codes to leverage these powerful new heterogeneous systems. We present our work on addressing the extreme-scale computing challenges in computational fluid dynamics, ensuring exascale readiness of turbulence simulations. Focusing on Neko, a high-fidelity spectral element code, we outline the optimisation and algorithmic work necessary to ensure scalability and performance portability across a wide range of platforms. Finally, we present performance measurements on a wide range of accelerated computing platforms, including the EuroHPC pre-exascale systems LUMI and Leonardo, where Neko achieves excellent parallel efficiency for an extreme-scale direct numerical simulation (DNS) of turbulent thermal convection using up to 80% of the entire LUMI supercomputer.

Enabling mixed-precision with VerifiCarlo: Sharing CEEC experience
2025-03-04 10:00 - 11:00
Join our own Roman Iakymchuk, Umeå University on behalf of CEEC, and Pablo de Oliveira Castro, Université Paris-Saclay UVSQ, for the next in our webinar series this time on mixed precision and 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.

3rd CEEC Community Workshop - Vistle Part II: Hands-On Workshop for 3D Data Visualization
2025-05-21 15:00 - 17:00 | 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.
