Session

DescriptionOrganizer(s): Ahmad Nawab, Michael Lange, and Balthasar Reuter (ECMWF)

Fortran, the primary programming language underpinning many operational weather and climate codes, was built around the fundamental principle that performance optimisation is left to the compiler. However, to fully utilise modern HPC architectures and GPUs, additional programming paradigms as well as invasive code changes are often needed. While high-level DSLs or C-based abstraction layers like Kokkos provide a disruptive path to performance portability, for Fortran such abstractions are lacking. This leads to the fundamental question “What the actual FORTRAN can we do to achieve performance portability for complex physical models?” In this minisymposium we continue this discussion by looking at cross-architecture portability of ecWAM, ECMWF’s operational wave model. ecWAM is a key component of ECMWF’s Integrated Forecasting System (IFS), and is also used operationally in all the IFS-derived Destination Earth digital twins. We highlight the complexities and challenges that its diverse range of computing patterns pose, and together with industrial and academic partners, discuss different strategies towards a maintainable cross-platform adaptation strategy that runs efficiently across different HPC architectures. As ecWAM shares many similarities with other scientifically state-of-the-art third generation wave models, this minisymposium potentially offers a wide-ranging impact across the weather and climate communities.