That Old PlayStation Can Aid Science

Gaurav Khanna with a supercomputer he built at the University of Massachusetts Dartmouth physics department. Credit Dominick Reuter for The New York Times

This spring, Gaurav Khanna noticed that the University of Massachusetts Dartmouth physics department was more crowded than usual. Why, he wondered, were so many students suddenly so interested in science?

It wasn’t a thirst for knowledge, it turns out. News of Dr. Khanna’s success in building a supercomputer using only PlayStation 3 video game consoles had spread quickly; the students, a lot of them gamers, just wanted to gape at the sight of nearly 200 consoles stacked on one another.

“It caused quite a stir around here,” Dr. Khanna said.

A black hole physicist and associate director of the university’s Center for Scientific Computing and Visualization Research, Dr. Khanna first networked 16 PlayStation 3 consoles in 2007 to help model black hole collisions.

His research is focused on finding and studying gravitational waves, vibrations that ripple through space-time. The waves, first predicted by Einstein’s theory of general relativity, form after a particularly violent astrophysical event, like two black holes smashing together. Because black holes cannot be observed through telescopes, Dr. Khanna uses supercomputers to create simulations of these collisions.

The 200 Playstation 3 consoles that comprise the supercomputer are housed in a refrigerated shipping container. Credit Dominick Reuter for The New York Times

Supercomputers have become an increasingly important tool for scientists and engineers, who rely on them to crunch large numbers and solve calculations too large for one processor to attempt. According to Dr. Khanna, a supercomputer performs at least 10 times as well as a single desktop computer. He refers to supercomputers as the “third pillar” of science, behind theory and experimentation.

“Science has become expensive,” he said. “There’s simply not that much money going around, either at the university or the federal level. Supercomputing allows scientists to make up for the resources they don’t have.”

Making a supercomputer requires a large number of processors — standard desktops, laptops or the like — and a way to network them. Dr. Khanna picked the PlayStation 3 for its viability and cost, currently, $250 to $300 in stores. Unlike other game consoles, the PlayStation 3 allows users to install a preferred operating system, making it attractive to programmers and developers. (The latest model, the PlayStation 4, does not have this feature.)

“Gaming had grown into a huge market,” Dr. Khanna said. “There’s a huge push for performance, meaning you can buy low-cost, high-performance hardware very easily. I could go out and buy 100 PlayStation 3 consoles at my neighborhood Best Buy, if I wanted.”

That is just what Dr. Khanna did, though on a smaller scale. Because the National Science Foundation, which funds much of Dr. Khanna’s research, might not have viewed the bulk buying of video game consoles as a responsible use of grant money, he reached out to Sony Computer Entertainment America, the company behind the PlayStation 3. Sony donated four consoles to the experiment; Dr. Khanna’s university paid for eight more, and Dr. Khanna bought another four. He then installed the Linux operating system on all 16 consoles, plugged them into the Internet and booted up the supercomputer.

 

Lior Burko, an associate professor of physics at Georgia Gwinnett College and a past collaborator with Dr. Khanna, praised the idea as an “ingenious” way to get the function of a supercomputer without the prohibitive expense.

“Dr. Khanna was able to combine his two fields of expertise, namely general relativity and computer science, to invent something new that allowed for not just a neat new machine, but also scientific progress that otherwise might have taken many more years to achieve,” Dr. Burko said.

In 2009, Dr. Khanna published a paper in the journal Parallel and Distributed Computing and Systems demonstrating the cell processor of the PlayStation 3 was able to speed up scientific calculations over a traditional computer processor by a factor of nearly 10. The first results of simulations made using the PlayStation 3 supercomputer, detailing the behavior of gravitational waves arising from rotating black holes, were published the same year in the journal Classical and Quantum Gravity.

Dr. Khanna’s observations caught the attention of the Air Force Research Laboratory in Rome, N.Y., whose scientists were investigating PlayStation 3 processors. In 2010, the lab built its own PlayStation 3 supercomputer using 1,716 consoles to conduct radar image processing for urban surveillance. “Our PS3 supercomputer is capable of processing the complex computations required to create a detailed image of an entire city from radar data,” said Mark Barnell, the director of high performance computing at the Air Force Research Laboratory. The lab later entered into a cooperative research-and-development agreement with Dr. Khanna’s team, donating 176 PlayStation 3 consoles.

His team linked the consoles, housing them in a refrigerated shipping container designed to carry milk. The resulting supercomputer, Dr. Khanna said, had the computational power of nearly 3,000 laptop or desktop processors, and cost only $75,000 to make — about a tenth the cost of a comparable supercomputer made using traditional parts.

Dr. Khanna has since published two more papers on black hole collisions with results from simulations on the PlayStation 3 supercomputer. Later this year, another 220 consoles from the Air Force lab will arrive. While the plan is to use the consoles to perform more involved and accurate simulations of black hole systems, Dr. Khanna has invited colleagues from other departments to use the supercomputer for their own projects: An engineering team, for example, has signed on to conduct simulations that will help design better windmill blades and ocean wave energy converters, and the university’s math department would like to use the supercomputer as a tool to attract students into areas like computational math and science.

But the PlayStation 3 supercomputer isn’t suited to all scientific applications. Its biggest limitation is memory: The consoles have very little compared with traditional supercomputers, meaning they cannot handle large-scale calculations. One alternative is to switch to an even better processor, like PC graphics cards. These are also low-cost and extremely powerful — each card is the equivalent of 20 PlayStation 3 consoles in terms of performance.

“The next supercomputer we’re going to build will probably be made entirely of these cards,” Dr. Khanna said. “It won’t work for everything, but it will certainly cover a large set of scientific and engineering applications, especially if we keep improving on it.”