National Center for Computational Sciences

Venerable vector system retired as next generation comes on line

ORNL’s Phoenix supercomputer, still one of the fastest vector systems in the world, was taken out of service at the beginning of October to make way for petascale systems capable of 1,000 trillion calculations a second (1 petaflop).

Installed in 2003 with a peak performance of 3.2 trillion calculations a second (3.2 teraflops), Phoenix was ORNL’s most powerful system when the lab’s Leadership Computing Facility was established in 2004. It has been upgraded in the years since and in its latest configuration had more than 1,000 multistreaming vector processors and a peak performance of more than 18 teraflops. In its 5½ years at ORNL, Phoenix rose as high as No. 17 on the TOP500 list of the world’s fastest supercomputers.

At the time it was installed, supercomputing was still dominated by Japan’s Earth Simulator, but both systems have long been surpassed. In fact, Phoenix is being removed from ORNL’s computer room to make way for two systems that are each more than 300 times as powerful as that 3.2-teraflop configuration. The NCCS’s Cray XT5 Jaguar system will boast a peak performance of 1 petaflop, while the National Institute for Computational Sciences’ Cray XT5 Kraken system will peak at just under that level.

In its time Phoenix was critically important to progress in fields such as computational fluid dynamics, climate science, fusion studies, astrophysics, and materials science. “Many of our users loved working on Phoenix,” said NCCS Director of Science Doug Kothe. “It was a fantastic machine.”

ORNL’s Anthony Mezzacappa and colleagues used the system to advance the world’s understanding of core-collapse supernovae. The team first discovered that the shockwave created by a star’s collapsing iron core becomes unstable and wobbly before it blows most of the star into space. Later it showed that this instability is very possibly responsible for the pulsar that is all that remains of the star.

“My heart sank a little when Phoenix was finally turned off, and not just for sentimental reasons,” said Bronson Messer of the NCCS, a member of Mezzacappa’s team who first used Phoenix while he was a postdoctoral researcher at the University of Chicago. “The machine was remarkably capable even at the end of its tenure and allowed us to perform supernova simulations—ranging from the birth of pulsars to the signature of galactic supernovae in terrestrial neutrino detectors—with amazing efficiency.”

Climate scientists moved to Phoenix and found it to be a great advance over earlier systems used to provide data for the IPCC AR4.

“We saw a factor-of-15 increase in speed over current production,” noted John Drake, chief computational scientist for the Climate End Station at ORNL. “It was a great machine for climate simulation.”

ORNL’s Thomas Schulthess and colleagues used Phoenix to make a major breakthrough in materials science, showing that a model known as the 2D Hubbard model correctly describes high-temperature superconductors where more conventional density functional theory fails. The team’s discovery moved forward a line of research that may eventually prove revolutionary in areas such as electric-power generation, electronics, and transportation.

“We did important work on Phoenix,” said ORNL’s Thomas Maier, a member of Schulthess’s team.

Kothe noted that while Phoenix’s passing marks the end of an era, the system is moving out for the best of reasons.

“We hate to see this great vector hardware and software leave,” he acknowledged, “but we expect these petascale systems to enable unprecedented advances in computational research, and we’ll very likely see more vector hardware in next-generation systems.”