The first supercomputer to break the petaflop barrier — one trillion calculations per second — was decommissioned on Sunday.
Roadrunner was part of the National Nuclear Security Administration’s Advanced Simulation and Computing (ASC) program designed to provide key computer simulations for the Stockpile Stewardship Program.
During its five operational years it was a workhorse system providing computing power for stewardship of the US nuclear weapon stockpile as well as a wide variety of unclassified science projects.
The IBM system achieved petaflop speed in 2008, shortly after installation at Los Alamos National Laboratory.
"Roadrunner was a truly pioneering idea," said Gary Grider of the Laboratory's High Performance Computing Division. "Roadrunner got everyone thinking in new ways about how to build and use a supercomputer. Specialized processors are being included in new ways on new systems, and being used in novel ways. Our demonstration with Roadrunner caused everyone to pay attention."
Roadrunner's design was controversial in that it combined two different kinds of processors, making it a “hybrid”.
It had 6,563 dual-core general-purpose AMD Opterons processors, with each core linked to a special PowerXCell 8i graphics processor called a “Cell.” The Cell was an enhanced version of a specialized processor originally designed for the Sony Playstation 3, adapted specifically to support scientific computing.
Although other hybrid computers existed, none were at the supercomputing scale and many doubted that a hybrid supercomputer could work, making Roadrunner a leap of faith.
High-speed calculation was the primary goal in particular to address the long-standing gap in understanding of energy flow in a nuclear weapon and its relation to weapon yield.
In the area of general science, Roadrunner provided a platform to study a wide variety of scientific unknowns at an unprecedented scale including nanowire material behaviour, magnetic reconnection, laser backscatter, HIV phylogenetics, and a simulation of the universe at a 70-billion-particle scale.
"What Roadrunner did was exactly what it was intended to do: get the weapons codes moving toward new architectures," said Cheryl Wampler of the Weapons Physics directorate. "Roadrunner was challenging because the supercomputing future was challenging."
Future supercomputers will need to improve on Roadrunner’s energy efficiency to make the power bill affordable and learn how to cope with the sheer volume of data produced.
But advancements made possible by Roadrunner have informed current computing architectures and will help shape future designs.
"Even in death," said Grider, "we are trying to learn from Roadrunner."
After the machine is shut off but before it is dismantled, researchers will have a about one month to do experiments on operating system memory compression techniques for an ASC relevant application, and optimized data routing to help guide the design of future capacity cluster computers.
"These are things we never could try while Roadrunner was running production problems," Grider added.