CEEC CoE

Sustainable and Reliable Computing with Tools: Analyzing Precision Appetites of CFD Applications with VerifiCarlo
2023-06-27 16:30 - 17:00 (Europe/Paris)
The energy consumption constraint for large-scale computing encourages scientists to revise the architecture design of hardware but also applications, algorithms, as well as the underlying working/ storage precision. The main aim is to make the computing cost sustainable and apply the lagom principle (”not too much, not too little, the right amount”), especially when it comes to working/ storage precision. Thus, I will introduce an approach to address the issue of sustainable, but still reliable, computations from the perspective of computer arithmetic tools. Before lowering precision, one needs to ensure that the simulation is numerically correct, e.g. by relying on alternative floating-point models/ rounding to pinpoint numerical bugs and to estimate the accuracy. We employ VerifiCarlo and its variable precision backend to identify the parts of the code that benefit from smaller floating-point formats. Finally, we show preliminary results on proxies of CFD applications.

MS4F - Cross-Cutting Aspects of Exploiting Exascale Platforms for High-Fidelity CFD in Turbulence Research
2023-06-27 16:00 - 18:00
With the arrival of exascale computing, the theoretical computational performance has increased, opening up for unprecedented simulation capabilities for Computational Fluid Dynamics (CFD) applications. While offering high theoretical peak performance and high memory bandwidth, to efficiently exploit these systems, complex programming models and significant programming investments are necessary. Furthermore, most known pre and exascale systems currently planned or installed, e.g. Frontier, Leonardo and LUMI, contain a large fraction of accelerators. Thus, the challenge of porting and tuning scientific codes for these new platforms can no longer be ignored. However, established CFD codes build on years of verification and validation of their underlying numerical methods, potentially preventing a complete rewrite and rendering disruptive code changes a delicate task. Therefore, porting established codes to accelerators poses several interdisciplinary challenges, from formulating suitable numerical methods to applying sound software engineering practices to cope with disruptive code changes. The wide range of topics makes the exascale CFD transition relevant to a broader audience, extending outside the traditional fluid dynamics community. This minisymposium aims at bringing together the CFD community as a whole, from domain scientists to HPC experts, to discuss current and future challenges towards enabling exascale fluid dynamics simulations on anticipated accelerated systems.

Neko: A Modern, Portable, and Scalable Framework for High-Fidelity Computational Fluid Dynamics
2023-06-01 17:00 - 17:30
Recent trends and advancements including more diverse and heterogeneous hardware in High-Performance Computing are challenging scientific software developers in their pursuit of good performance and efficient numerical methods. As a result, the well-known maxim “software outlives hardware” may no longer necessarily hold true, and researchers are today forced to re-factor their codes to leverage these powerful new heterogeneous systems. We present Neko – a portable framework for high-fidelity spectral element flow simulations. Unlike prior works, Neko adopts a modern object-oriented Fortran 2008 approach, allowing multi-tier abstractions of the solver stack and facilitating various hardware backends ranging from general-purpose processors, accelerators down to exotic vector processors and Field-Programmable Gate Arrays (FPGAs) via Neko’s device abstraction layer. Focusing on the performance and accuracy of Neko, we show the first direct numerical simulation (DNS) of a Flettner rotor submerged in a turbulent boundary layer, observing excellent agreement of lift with experimental data. Using a mesh with five million spectral elements, which turns into more than a billion unique degrees of freedom, the simulation requires less than three days to complete on accelerated systems compared to weeks on traditional non-accelerated systems. Finally, we present performance measurements on a wide range of accelerated computing platforms, including the EuroHPC pre-exascale system LUMI, where Neko achieves excellent parallel efficiency for a large DNS of turbulent fluid flow using up to 80% of the entire LUMI supercomputer.

Reliable and sustainable computations: An application-driven approach
2023-05-24 14:40 - 15:00
In this talk, Roman Iakymchuk presents his work on accuracy and reproducibility assuring strategies for parallel iterative solvers that may not hold due to the non-associativity of floating-point operations. These strategies primarily rely on guarding every bit of result until final rounding, hence they can be costly. The energy consumption constraint for large-scale computing encourages scientists to revise the architecture design of hardware but also applications, algorithms, as well as the underlying working/ storage precision. The main aim is to make the computing cost sustainable and apply the lagom principle (”not too much, not too little, the right amount”), especially when it comes to working/ storage precision. Thus, he will introduce an approach to address the issue of sustainable, but still reliable, computations from the perspective of computer arithmetic tools. Before lowering precision, one must ensure that the simulation is numerically correct, e.g. by relying on alternative floating-point models/ rounding to pinpoint numerical bugs and to estimate the accuracy. We employ VerifiCarlo and its variable precision backend to identify the parts of the code that benefit from smaller floating-point formats. Finally, we show preliminary results on proxy applications.

Introducing CEEC at ISC23
2023-05-24 11:45 - 12:15
Come learn about CEEC at the European HPC Joint Undertaking booth at ISC23! We’ll give a quick overview of the project and be eager to answer all your questions about CFD, our lighthouse cases, and how our work can help address grand challenges.

ISC High Performance 2023
2023-05-21 - 2023-05-25
Come visit us at the EuroHPC Joint Undertaking booth B201 at ISC! We will be there all week to answer your questions about our goals, future work, and its potential impact on the field of computational fluid dynamics. Once again in Hamburg, the annual ISC event is sure to offer something for every person interested in HPC, machine learning, data analytics, and quantum computing.

"Scalable High-Fidelity Simulation of Turbulence With Neko Using Accelerators" CUG 2023 “Sustainable Exascale”
2023-05-11 14:00 - 14:30 | CSCT Center for Science Ltd (CSC Finland), Helsinki, Finland
It’s time again for the annual Cray User Group (CUG) conference: this time in Finland! We’ll be contributing to the discussions on how to best use Cray and HPE supercomputers with a paper titled, “Scalable High-Fidelity Simulation of Turbulence With Neko Using Accelerators”. You will also be able to read the paper on our publication page after the conference.
