Parallelization and Performance of the NIM Weather Model on CPU, GPU and MIC Processors

Abstract

he design and performance of the NIM global weather prediction model is described. NIM is a dynamical core designed to run on CPU, GPU and MIC processors. It demonstrates efficient parallel performance and scalability to tens of thousands of compute nodes, and has been an effective way to make comparisons between traditional CPU and emerging fine-grain processors. The design of the NIM also serves as a useful guide in the fine-grain parallelization of the FV3 model recently chosen by the NWS to become its next operational, global weather prediction model.This paper describes the code structure and parallelization of NIM using standards-compliant OpenMP and OpenACC directives. NIM uses the directives to support a single, performance-portable code that runs on CPU, GPU and MIC systems. Performance results are compared for five generations of computer chips including the recently released Intel Knights Landing and NVIDIA Pascal chips. Single and multi-node performance and scalability is also shown, along with a cost-benefit comparison based on vendor list prices.