Influence of the compiler on multi-CPU performance of WRFv3

The Weather Research and Forecasting system version 3 (WRFv3) is an open source and state of the art numerical Regional Climate Model used in climate related sciences. These years the model has been successfully optimized on a wide variety of clustered compute nodes connected with high speed interconnects. This is currently the most used hardware architecture for high-performance computing (Shainer et al., 2009). As such, understanding the influence of hardware like the CPU, its interconnects, or the software on WRFs performance is crucial for saving computing time. This is important because computing time in general is rare, resource intensive, and hence very expensive. This paper evaluates the influence of different compilers on WRFs performance, which was found to differ up to 26%. The paper also evaluates the performance of different Message Passing Interface library versions, a software which is needed for multi CPU runs, and of different WRF versions. Both showed no significant influence on the performance for this test case on the used High Performance Cluster (HPC) hardware. Emphasis is also laid on the applied non-standard method of performance measuring, which was required because of performance fluctuations between identical runs on the used HPC. Those are caused by contention for network resources, a phenomenon examined for many HPCs (Wright et al., 2009).