CppCon 2014

What is the link between C++11/14, parallelism and the open question of the origin of the accelerated expansion of the Universe ? Answer: numerical cosmology and all the techniques to make the best out of supercomputers to shed a new light on unsolved problem in physics. In this talk, I will present the numerical lessons coming from the Full Universe Run, a numerical experiment realized in 2012 on the entire Curie thin-nodes Supercomputer to simulate the evolution of cosmological structures during the last 13.7 billion years. I will focus on how this experiment has changed our view on software design in astrophysics and how we started to implement new approaches using C++11, template metaprogramming, constant expressions and std::thread in order to maximize both genericity and performance. I will also discuss optimization issues related to data locality, cache efficiency and spatial trees which are extensively used in our domain. I will also try to give some inputs on the cultural challenges raised by the introduction of C++11/14 in our domain. This talk will be concluded by thoughts on the needs of computational physicists and how C++17 may help us to solve some of the open problems we are currently facing.