Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

High fidelity Computational Fluid Dynamics simulations are generally associated with large computing requirements, which are progressively acute with each new generation of supercomputers. However, significant research efforts are required to unlock the computing power of leading-edge systems, currently referred to as pre-Exascale systems, based on increasingly complex architectures. In this paper, we present the approach implemented in the computational mechanics code Alya. We describe in detail the parallelization strategy implemented to fully exploit the different levels of parallelism, together with a novel co-execution method for the efficient utilization of heterogeneous CPU/GPU architectures. The latter is based on a multi-code co-execution approach with a dynamic load balancing mechanism. The assessment of the performance of all the proposed strategies has been carried out for airplane simulations on the POWER9 architecture accelerated with NVIDIA Volta V100 GPUs.This work is partially supported by the BSC-IBM Deep Learning Research Agreement, under JSA \Application porting, analysis and optimization for POWER and POWER AI". It has also been partially supported by the EX-CELLERAT project funded by the European Commission's ICT activity of the H2020 Programme under grant agreement number: 823691. It has also received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number: 846139 (Exa-FireFlows). This paper expresses the opinions of the authors and not necessarily those of the European Commission. The European Commission is not liable for any use that may be made of the information contained in this paper. This work has also been nan- cially supported by the Ministerio de Economia, Industria y Competitividad, of Spain (TRA2017-88508-R). The computing experiments of this paper have been performed on the resources of the Barcelona Supercomputing Center.Peer Reviewe