Performance-optimized co-design of ocean modeling software on FPGAs

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Modern flooding/weather/climate prediction models critically rely on sophisticated numerical methods and ever increasing spatial and temporal resolution to deliver more accurate and physically comprehensive simulations. Also more detailed physics and more complex numerical schemes better representing subgrid scale effects are certainly high on the agenda. However, running high-resolution models on planet- or even region-sized domains sets a very high bar for the computational and energy efficiency of model codes on modern and future parallel and hybrid architectures. In particular, HPC systems with energy-efficient FPGA accelerators and special data-flow-oriented execution models offer special potential, but also require completely new approaches for the software development of earth system models.With this project, we propose to substantially advance the state of the art by combining several innovative methodologies from computer science, numerical algorithms, and grid generation within a comprehensive software/hardware co-design concept to deliver previously unattainable computational and energy performance levels. The proposed work extensively utilizes the techniques and tools created in the scope of the existing cooperations between Prof. Aizinger and Dr. Grosso and between Dr. Kenter and Prof. Aizinger.The application in the focus of the project is an ocean model that combines a number of key physical, mathematical, and numerical aspects specific to geophysical and climate applications. These include very large, geometrically complex domains which require numerical methods with high accuracy, local conservation of important physical quantities, low numerical diffusion, support of unstructured meshes, and good parallelization properties. The key ingredients of the proposed project are: An FPGA-optimized discontinuous Galerkin (DG) solver based on the UTBEST code, block-structured meshes of unique makeup -- supporting blocks with and without inner structure -- a further development of methodology first introduced in DFG GR 1107/3-1, and a~data flow FPGA design utilizing OpenCL and optimized for such combined block meshes.The developed methodologies and techniques will be implemented in the form of a technology demonstrator (open access) and applied to realistic showcase flooding scenarios on a high resolution mesh. Beyond the concrete demonstrator, a success of this integrative inter-disciplinary work has, in our opinion, a significant methodological added value that can subsequently shape more ambitious projects in this and related areas, while also establishing the institutional foundations for participation in such projects.