Porting a Computational Fluid Dynamics Code with AMR to Large-scale GPU Platforms.

Accurate modeling of turbulent hypersonic flows has tremendous scientific and commercial value, and applies to atmospheric flight, supersonic combustion, materials discovery and climate prediction. In this paper, we describe our experiences in extending the capabilities of and modernizing CRoCCo, an MPIbased, CPU-only compressible computational fluid dynamics code. We extend CRoCCo to support block-structured adaptive mesh refinement using a highly-scalable AMR library, AMReX, and add support for a fully curvilinear solver. We also port the computational kernels in CRoCCo to GPUs to enable scaling on modern exascale systems. We present our techniques for overcoming performance challenges and evaluate the updated code, CRoCCo v2.0, on the Summit system, demonstrating a 6x to 44x speedup over the CPU-only version.