The Centre for Computational Astrophysics (CfCA) operates supercomputers for astronomical simulations. The Cray XC30 system named “ATERUI”, installed at the NAOJ Mizusawa campus in April 2013, is the National Astronomical Observatory of Japan’s (NAOJ’s) 4th-generation supercomputer for numerical simulation. This system is a scalar type massively parallel supercomputer. With the theoretical peak performance of 502 Tflops, ATERUI was the world’s fastest supercomputer dedicated to astronomical simulation. It accelerated our understanding in various fields of astrophysics, but astronomers’ requirements for computer performance have become higher and higher.
Upgrade of ATERUI
Responding to the increasing demand, ATERUI had “surgery” to introduce a new “brain” 11th-30th September, 2014. In this operation, the old CPUs were exchanged with new CPUs. The number of cabinets decreased from 8 to 6, and the interconnects between CPUs were reconnected. Although the number of cabinets decreased, the theoretical peak performance approximately doubled from 502 Tflops to 1058 Tflops(=1.058 Pflops). This means that the upgraded computer can perform one thousand trillion calculations per second. This marks the best performance in the world for an astronomical simulation supercomputer. ATERUI became the first petaflops supercomputer operated by NAOJ.
The renewed ATERUI has started operation from 1st October, 2014 and 127 researchers have been using this new system. The users include researchers and graduate students not only in NAOJ, but also in universities and other institutes in Japan, and Japanese researchers abroad. ATERUI runs various simulations: the formation of planets, the birth and death of stars, the activity of the Sun, the evolution of black holes, the formation of galaxies and clusters of galaxies and the large scale structure of the universe.
For example, in simulations of supernovae and mergers of binary neutron stars, the complicated high-energy physics has to be considered. These simulations need huge computing power, and the new ATERUI will conduct more realistic simulations for these complicated phenomena. In addition, smaller time steps for calculations provide more accurate behaviours for phenomena. The new ATERUI will be able to follow more accurately the motions of particles like stars and fluids like interstellar gas or plasma gas. Moreover, higher spatial resolution provides fine structure for celestial objects and the structure of the universe. For example, one simulation with new ATERUI can provide various views of the universe ranging from the large-scale structure down to the scale of individual galaxies.
Professor Eiichiro Kokubo, the CfCA project director says, “Supercomputers for astronomical researches can be called ‘telescopes for theoretical astronomy’ because they illustrate astrophysical phenomena that telescopes cannot see. New visions of the Universe which have never been seen before will be revealed by more realistic simulations using the new ATERUI”.
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