HOPPS: A performance portable spectral difference solver for high-fidelity computational fluid dynamics

High-fidelity computational fluid dynamics (CFD) enables the study of complex and subtle fluid dynamics phenomena, but remains to this day very computationally expensive. Therefore, being able to take advantage of all the raw compute power provided by high-performance computing (HPC) hardware evolutions such as the rise of GPU computing is key to making high-fidelity CFD more affordable. However, considering the diverse and fast-evolving HPC hardware landscape, long-term sustainability and software maintainability can rapidly be compromised. The use of adequate numerical methods is also key to reduce the computational cost, and discontinuous high-order methods which combine geometric flexibility and efficient hardware use in an increasingly bandwidth-bound HPC landscape, are very promising in this regard. This work reports the implementation of such a high-order CFD solver using the open source library Kokkos to address the performance portability and sustainability issues. Performance is investigated over a broad range of CPU and GPU architectures, demonstrating the relevance of the approach. This work also highlights the fitness of the chosen numerical method to achieve high orders of accuracy without compromising performance nor scalability.