Towards Operational Implementation of COSMO on Accelerators at MeteoSwiss

Oliver Fuhrer

Oliver Fuhrer
Federal Office of Meteorology and Climatology MeteoSwiss
Zurich, Switzerland


Higher grid resolution, larger ensembles as well as growing complexity of weather and climate models demand ever-increasing compute power. In 2013, several large hybrid high performance computers that contain traditional CPUs as well as some type of accelerator (e.g. GPUs) are online and available to the user community. Reasons for this development are an increase in computing performance in parallel with decreasing power consumption offered by such accelerators. This trend is foreseen to continue in the coming years, as many compute centers have an upper limit in terms of an acceptable power envelope. Early adopters of this technology trend may have considerable advantages in terms of available resources and energy-to-solution. On the downside, a substantial investment is required in order to adapt applications to such accelerator-based supercomputer.

Within the COSMO Consortium and the Swiss HP2C Initiative, a version of the weather and regional climate prediction model able to run on GPUs is being developed. This contribution will give an overview of the status of this version and present a roadmap of further plans. The adaptions that have been made to the model (and why these adaptions will also profit CPU-based hardware architectures) will be presented. While the physical parameterizations have been ported to GPUs using compiler directives, a more fundamental change of programming model has been used for the dynamics. We will discuss our experience and advantages and disadvantages of these two porting approaches. Finally, results from a demonstration project implementing COSMO on a server with eight GPUs and comparing its performance against a traditional CPU-based system will be presented.