By Amanda Onion
N E W Y O R K, June 2
— Forget multitasking — imagine how good you could become at doing one thing if that were all you ever did.
Developers have taken that idea and applied it to something much more capable of performing boring, repetitive tasks — the computer. The result is GRAPE 6, a supercomputer that will reportedly become the most powerful computer in the world. But don’t expect to put it on your desktop, unless all you want to do is compute gravitational force.
“A general computer with comparable speed would take up an entire auditorium,” explains Piet Hut, a professor of Astrophysics at the Institute of Advanced Study and co-developer of the new computer. “Here, there is no program, no intelligence. It just computes.”
The GRAPE History
Developers at the University of Tokyo began work on the GRAPE (an acronym for “gravity pipeline” and an intended pun on the Apple line of computers) in 1989. GRAPE 6’s predecessors include the GRAPE 4, which has already contributed to big findings in the field of astrophysics.
Attached to a PC, the supercomputer receives data at one end of a credit card-sized chip. The information ranging from the mass, size and location of any particle in space then enters through one of 16 pipelines inside the chip. Once each pipeline is filled with data, the computed results are immediately spit out the other end and fed into the PC.
David Ayd, a supercomputing manager at IBM, says the GRAPE 6 computer appears to be based on a very old model.
“In the 1970s and ’80s these vector models were developed in Japan for problems like simulating weather and plane mechanics,” he said. “The difference today is that the computers can do the jobs at 100 times the speed or faster.” Still, in July of 1995, the GRAPE 4 became the world’s fastest computer, breaking the 1 teraflop barrier with a peak speed of 1.08 TFLOPS.
FLOPS, short for floating-point operations per second, are a common measurement for microprocessors. Supercomputers are usually rated in terms of megaflops, gigaflops, teraflops and even petaflops.
A Massive FLOP
On Thursday Hut and others presented one board of the computer to the new Rose Center for Earth and Space in New York for the use of the center’s 12 astrophysicists. The board consists of 18 credit-card-sized chips which each contain six data pipelines. The single board, which is small enough to fit into a briefcase, can compute at a rate of 500 billion FLOPS. The final GRAPE model, when it’s finished in a year and a half, will consist of 200 of these boards and will operate at a speed of more than 100 trillion point operations per second.
That kind of speed becomes very useful when it comes to understanding the cosmos.
“If you take a large cluster of stars, it’s fundamentally impossible to figure out what happens because you need to calculate each star’s gravitational pull on every other star,” said Michael Shara, the curator-in-charge of the Astrophysics Department at the American Museum of Natural History (AMNH). “For a cluster of 1 million stars, that’s a trillion calculations every second.”
On its own, GRAPE 6 isn’t very useful. Instead, it must be plugged into another computer that effectively serves as its accountant. The regular computer takes care of the mundane data, such as calculating how many stars there are and their locations. It then feeds the appropriate information to GRAPE to calculate gravitational forces.
Shara says GRAPE’s capability to calculate gravity frame by frame, has already changed the face of astrophysical theories.
“It’s like those car crash tests,” he said. “The laboratory crashes allow you to observe what happens to each car during the crash. But it’s not realistic. It’s better to look at a whole city over a long period of time to see all the possible outcomes of a collision.”
Off the Charts
Astrophysicists, he explains, have commonly focused their calculations on smaller regions of the universe simply because calculating the gravitational pull of so many elements is daunting. With GRAPE 6, it becomes possible not only to chart the probable paths of, say, two stars, but entire galaxies. That’s a lot of number crunching considering the Milky Way galaxy is packed with about 400 billion stars, including the sun.
“It’s like a third branch of astrophysics has opened up in recent years,” said Mordecai Mark Mac Low, associate curator of astrophysics at the AMNH. “We’ve had theorists, observers and now we have computational astrophysicists.”
Some, however, caution that in the world of supercomputers, the GRAPE 6 isn’t really a contender. Ayd points out that supercomputers generally have more than one function. “You can’t use these simple computers for many things and that’s a drawback,” he says.
Still, from inside the domed theater of the AMNH’s Hayden Planetarium, it’s easy to appreciate the narrow effectiveness of the GRAPE 6. During a recent demonstration, astrophysicists projected graceful visualizations of stars colliding, galaxies converging and moons forming — as calculated by this very single-minded computer.
Frank Summers, an astrophysicist at AMNH, says the newly calculated visualizations represent only the beginning.
“Give us the largest computer you can build and we’ll fill it with our calculations,” he said. “We have the entire universe to compute.” 
|
|
W E B L I N K S
American Museum of Natural History
 A R C H I V E
Read Past Cutting Edge Columns
|
HOME
