Redesigning CAM-SE for Peta-Scale Climate Modeling Performance and Ultra-High Resolution on Sunway TaihuLight

The Community Atmosphere Model (CAM) is ported, redesigned, and scaled to the full system of the Sunway TaihuLight, and provides peta-scale climate modeling performance. We refactored and optimized the complete code using OpenACC directives at the first stage. A more aggressive and finer-grained redesign is then applied on the CAM, to achieve finer memory control and usage, more efficient vectorization and compute and communication overlapping. We further improve the CAM performance of a 260-core Sunway processor to the range of 28 to 184 Intel CPU cores, and achieve a sustainable double-precision performance of 3.3 PFlops for a 750 m global simulation when using 10,075,000 cores. CAM on Sunway achieves the simulation speed of 3.4 and 21.5 simulation-year-perday (SYPD) for global 25-km and 100-km resolution respectively; and enables us to perform, to our knowledge, the first simulation of the complete lifecycle of hurricane Katrina, and achieve close-toobservation simulation results for both track and intensity.