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

现代洪水/天气/气候预测模型严重依赖复杂的数值方法和不断提高的空间和时间分辨率，以提供更准确和更全面的物理模拟。此外，更详细的物理和更复杂的数值方案，更好地代表次网格尺度效应，肯定是议程上的优先事项。然而，在行星甚至区域大小的域上运行高分辨率模型，对现代和未来并行和混合体系结构上的模型代码的计算和能源效率设置了非常高的标准。特别是，具有节能的FPGA加速器和特殊的面向数据流的执行模型的高性能计算系统提供了特殊的潜力，但也需要全新的方法来开发地球系统模型的软件。通过这个项目，我们建议通过将计算机科学、数值算法和网格生成的几种创新方法结合到一个全面的软硬件协同设计概念中来大幅提升最先进的技术水平，以提供以前无法达到的计算和能量性能水平。拟议的工作广泛利用了艾辛格教授和格罗索博士以及肯特博士和艾辛格教授之间现有合作范围内创建的技术和工具。该项目的重点应用是海洋模型，该模型结合了地球物理和气候应用的许多关键物理、数学和数值方面。这包括非常大的、几何复杂的区域，这需要高精度的数值方法、重要物理量的局部守恒、低数值扩散、非结构网格的支持和良好的并行化特性。该项目的关键部分包括：基于UTBEST代码的现场可编程门阵列优化的不连续伽辽金(DG)求解器，独特结构的块结构网格--支持内部结构的块和不带内部结构的块--DFG GR 1107/3-1中首次引入的方法的进一步发展，以及利用OpenCL进行数据流的FPGA设计并针对这种组合块网格进行优化。所开发的方法和技术将以技术演示(开放访问)的形式实现，并应用于高分辨率网格上的真实展示洪水场景。我们认为，除了具体的示范工作外，这种综合性跨学科工作的成功还具有重大的方法附加值，可以随后在这一领域和相关领域形成更雄心勃勃的项目，同时也为参与这些项目奠定体制基础。

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.