First steps with a big impact
With the third week of work in the books, it’s high time for another update here. We’ve been busy getting everything set up on ARCHER2 to be ready to run proper simulations and get into the performance measurement of the MPAS atmosphere model.
After some technical issues with downloading and compiling MPAS during the first week, we set our eyes on writing scripts to help automate future runs. As we intend on simulating a wide variety of scenarios using different parameters such as mesh size, model run time and number of nodes used, not having to manually change these for each run will save a lot of time in the future.
Last week we were finally were able to start running the first simulations. This wasn’t a real test scenario yet but a simple idealized case. Figure 1 shows the result of a Jablonowski & Williamson baroclinic wave modelled for 150 hours (just over 6 days) propagating across the Earth. This is a very simple test often used to see whether an atmospheric model fundamentally works. It models a single pressure wave propagating zonally across the Earth.
While not very exciting to look at, these kinds of tests help us to see whether MPAS is working properly and also gives us an important insight into how we can best design our upcoming experiments to make the best use of our time and computing budget. It also gives us a first look at the performance of the MPAS atmosphere model. As seen in the Figure, the average run time dropped from 1 to 3 cores, showing better performance with more computing power, but increased again when 4 cores were being used. This is most likely due to any performance gain by further parallelization of the model being diminished by more time spent in communication between the tasks. These are the kind of insights that we hope to find later in our performance analysis, but on a much bigger scale, and will investigate using profiling tools to pinpoint where performance is lost.
With the experiences gained from the last few weeks, we are now ready to start the proper performance analysis of MPAS, next up is debugging some of the automation scripts and running small scale simulations for our first real scenario. So, stay tuned for more updates!