Computing the Sky at Extreme Scales

The Exascale Universe

Cosmological structure formation from the HACC code’s ‘Q Continuum’ run on Titan. Smooth and featureless initial conditions evolve under gravity in an expanding universe to eventually form a complex ‘cosmic web’. The video shows a tiny fraction of the full simulation.

Modern cosmological observations have led to a remarkably successful model for the dynamics of the Universe. Three key ingredients — dark energy, dark matter, and inflation — are signposts to further breakthroughs, as all reach beyond the known boundaries of the particle physics Standard Model. A new generation of sky surveys will lead to key insights into these questions as well as provide new measurements, such as of neutrino masses; new discoveries, such as of primordial gravitational waves and modifications of general relativity are eagerly awaited.  Sophisticated, large-scale simulations of cosmic structure formation are essential to this scientific enterprise. Not only do they shed light on some of the deepest puzzles in all of physical science, but rank among the very largest and most scientifically rich simulations run on supercomputers today.

Two orders of magnitude gains in performance and increases in memory size will be required to address the new end-to-end challenge on exascale timescales, to be met by a comprehensive program using the HACC and Nyx codes. The extreme-scale framework, HACC, is designed for high performance, scalability, and the ability to run on all supercomputing platforms. The Eulerian AMR code Nyx will complement the Lagrangian nature of HACC; the two codes will be used to develop a joint program for verification of gravitational evolution, gasdynamics, and subgrid models in cosmological simulations at very high dynami


HACC code paper, Habib et al.

Nyx code paper, Almgren et  al.