Communication-Avoiding for Dynamical Core of Atmospheric General Circulation Model

Abstract

Dynamical core is one of the most time-consuming parts in the global atmospheric general circulation model, which is widely used for the numerical simulation of the dynamic evolution process of global atmosphere. Due to its complicated calculation procedures and the non-uniformity of latitude-longitude mesh, the parallelization suffers from high communication overhead. In this paper, we deduce the operator form of the calculating flow in the dynamical core. Furthermore, it is abstracted out that the stencil and collection alternate action is the basic operation in the dynamic core. Based on the operator form of the calculation flow, we propose the corresponding optimization strategy for each operator. In the end, we develop a communication-avoiding algorithm to reduce communication overhead in the dynamic core. Our experiments show that the communication-avoiding algorithm reduces the total runtime by 54% at most for a 50 km resolution model running 10 years. Especially for communication reduction, the new algorithm achieves 1.4x speedup on average for the collective communication and 3.9x speedup on average for the communication involved in the stencil computation.