Researchers used Frontier Supercomputer to Unveil the Largest Universe Simulation Ever

The world’s largest simulation of the universe lays a new computational basis for simultaneous extreme-scale dark matter and astrophysical investigations.

Researchers used the Frontier supercomputer to carry out the largest astrophysical simulation to date, simulating both atomic and dark matter across cosmos-sized scales. This was enabled by advancements in HACC, a code developed to run on exascale-class supercomputers, now capable of executing quintillion calculations per second. This breakthrough in cosmological hydrodynamics simulations will help in matching observational data with theoretical models.

Universe Simulation Breakthrough

The cosmos just expanded—at least in the dominion of computer simulations. Last month, experts at the Department of Energy’s Argonne National Laboratory harnessed the power of the world’s quickest supercomputer to carry out the largest astrophysical simulation of the cosmos ever accomplished.

This revolutionary simulation was made possible by the Frontier supercomputer at Oak Ridge National Laboratory. The calculations set a new standard for cosmological hydrodynamics, providing a pioneering approach to modelling both dark matter and atomic matter simultaneously. The simulation’s scale matches that of colossal telescope surveys, a competence that was earlier out of reach at this magnitude.

Advanced Cosmological Simulations at Exascale

“There are two components in the universe: dark matter — which as far as we know, only interacts gravitationally — and conventional matter, or atomic matter.” said project lead Salman Habib (division director for Computational Sciences at Argonne). “So, if we want to know what the universe is up to, we need to simulate both of these things: gravity as well as all the other physics including hot gas, and the formation of stars, black holes and galaxies,” he said. “The astrophysical ‘kitchen sink’ so to speak. These simulations are what we call cosmological hydrodynamics simulations.”

Overcoming Computational Challenges

Not unexpectedly, the cosmological hydrodynamics simulations are considerably more computationally expensive and much more difficult to perform compared to simulations of an expanding cosmos that only involve the effects of gravity. “For example, if we were to simulate a large chunk of the universe surveyed by one of the big telescopes such as the Rubin Observatory in Chile, you’re talking about looking at huge chunks of time — billions of years of expansion,” said Habib. “Until recently, we couldn’t even imagine doing such a large simulation like that except in the gravity-only approximation.”

Leveraging High-Performance Computing

The supercomputer code employed in the simulation is called HACC, short for Hardware/Hybrid Accelerated Cosmology Code. It was developed roughly 15 years ago for petascale machines. In 2012 and 2013, HACC was a finalist for the Association for Computing Machinery’s Gordon Bell Prize in computing.

Later, HACC was significantly upgraded as part of ExaSky, a special Habib led project within the Exascale Computing Project, or ECP (a $1.8 billion DOE initiative that ran from 2016 to 2024). The project brought together thousands of specialists to develop advanced scientific applications and software tools for the upcoming wave of exascale-class supercomputers capable of executing more than a quintillion, or a billion-billion, calculations per second.