Cosmological simulations on supercomputers

Simulations of astrophysical problems capable of answering questions like "How did the Milky Way form?" or "What is the origin of the spin of terrestrial planets?" require weeks of processing with sustained Teraflop, or even Petaflop, performance. This can be achieved only by utilizing supercomputers with thousands of processors. To meet this challenge, we have developed ChaNGa (former ParallelGravity), a parallel simulator for cosmological interaction based on the Charm++ parallel framework.ChaNGa is one of the first cosmological simulators to attempt scaling to thousands of processors. The approach used, based on parallelization via Charm++, has enabled unprecedented performance results on current large machines. We have scaled relatively small-sized simulations, which are the hardest ones to parallelize, to thousands of processors on various platforms. We will show the infrastructure of both the Charm++ framework and the ChaNGa simulator, together with the key features to scale to large configurations and corresponding results.