Performance comparison of the A-grid and C-grid shallow-water models on icosahedral grids

Abstract

This study uses a single software framework to compare the CPU performance of Arakawa A-grid (NICAM) and C-grid (MPAS) schemes for solving the shallow-water equations on icosahedral grids. The focus is on high-resolution weather prediction. Performance analysis shows the simpler structure of the A-grid equations enables compiler optimization-based efficiency gains that the C-grid equations cannot match. Strong scaling runs at 3.5 km resolution show the A-grid is three times faster than the C-grid, enabling the A-grid to run at 50% higher resolution in only 15% more time. A performance comparison with the MPAS shallow-water model is included which demonstrates that our software implementation of the C-grid is robust and comparisons are fair.