Using OpenACC to port large legacy climate and weather modeling code to GPUs

Abstract The purpose of this chapter is to describe a step-by-step porting approach for weather and climate model Fortran code to run on GPUs using CUDA and OpenACC. At the end of this chapter, the reader will have a basic understanding of: • How to use OpenACC to port components of a production weather and climate model achieving a gain of about a factor of 2.3 × in terms of time to solution and about a factor of 3 × in terms of energy to solution • The step-by-step approach to port large sections weather and climate model code with OpenACC • Optimizations that may be introduced to enhance performance further on GPU when using OpenACC