Scientists have for some time postulated that
"dark matter" could partially account for evidence of missing mass in
the universe, while the hypothetical form of energy known as "dark
energy" is the most popular way to explain recent observations that the
universe appears to be expanding at an accelerating rate and accounts
for 74 percent of the total mass-energy of the universe according to
the standard model of cosmology. To better understand these two
mysterious cosmic constituents scientists at the Los Alamos National
Laboratory (LANL) are using Roadrunner, the worldâs fastest supercomputer, to model one of the largest simulations of the distribution of matter in the universe.
Even though itâs looking at only a small
segment of the âoeaccessibleâ universe, the âoeRoadrunner Universeâ model
requires a petascale computer because, like the universe, itâs
mind-bendingly large. The modelâs basic unit is a particle with a mass
of approximately one billion suns (in order to sample galaxies with
masses of about a trillion suns), and it includes 64 billion and more
of those particles.
According to Salman Habib, of the Laboratoryâs
Nuclear and Particle Physics, Astrophysics and Cosmology group the
Roadrunner Universe model will help scientists really understand how to
more completely and more accurately describe the observable universe,
to assist in the design of future experiments and interpret
observations from ongoing observations like the Sloan Digital Sky
âoeWe are particularly interested in the Large Synoptic Survey Telescope (LSST) in Chile, in which LANL
is an institutional member, and DOE and NASAâs Joint Dark Energy
Mission (JDEM),â said Habib. âoeTo do the science in any sort of
reasonable amount of time requires a petascale machine at the least.â
The Roadrunner Universe model relies on a
hierarchical grid/particle algorithm that best matches the physical
aspects of the simulation to the hybrid architecture of Roadrunner.
Habib and his team wrote an entirely new computer code that
aggressively exploits Roadrunner's hybrid architecture and makes full
use of the PowerXCell 8i computational accelerators. They also created
a dedicated analysis and visualization software framework to handle the
huge simulation database.
âoeOur effort is aimed at pushing the current
state of the art by three orders of magnitude in terms of computational
and scientific throughput,â said Habib. Iâm confident the final
database created by Roadrunner will be an essential component of dark
universe science for years to come.â
As previously reported, the Roadrunner supercomputer was the first to break the petaflop barrier and it is being used for a number of projects aside from Habibâs teamâs efforts to model the origins of the unseen universe.
Other projects selected to use Roadrunner
include building the worldâs largest HIV evolutionary tree that may
lead researchers to new vaccine focus areas, simulating laser plasma
interactions to understand inertial confinement fusion,
and examining how nanowires break under stress to see how the movement
of single atoms can change a materialâs mechanical or electrical
properties. Sounds like it has plenty to keep it busy.