The Oak Ridge National Laboratory's new supercomputer is coming together, piece by piece. A team from IBM, the computer's manufacturer, has already begun installing computer cabinets for Summit, the country's next step between our current computing capabilities and a national goal to create the world's first exascale computer by 2021.

Oak Ridge Leadership Computing Facility project director Buddy Bland expects the rest of Summit's parts will arrive by February.

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"Then we would expect the machine to be built up and accepted sometime next summer," Bland said.

Test period

Once it's up and running, the lab will have what Bland calls a period of "early science," to allow the laboratory to explore the extent of the machine's capability.

The test period will allow ORNL scientists to look for any problems in the machine's set-up while they work on high-impact science experiments.

"We will try to run some big problems," Bland said, like testing and creating stronger, lighter manufacturing materials; using sound waves to model the inside of the Earth; and astrophysics projects exploring the origins of the universe.

"For instance, we'll be looking into why supernovae explode," he said. "When stars explode, they create all of the elements we find in the universe, everything that's part of you and me and part of this planet gets created."

The machine will become a user facility by early 2019. Scientists and researchers can then apply to use it to run their own experiments.

The guts

What makes Summit better for big science is what's inside, of course. Like Titan, Oak Ridge's current supercomputer, Summit will feature both central processing units and graphical processing units (GPUs) for what is called GPU-accelerated computing.

According to the units' manufacturer, NVIDIA, coupling the processors allows for accelerated analysis, deep learning, and engineering applications.

Central processing units, or CPUs, perform operations on most home computers and are well suited to querying data and performing mathematical equations. GPUs, on the other hand, were originally designed for the video-game industry.

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"They make very photorealistic video games, so when you're playing your video game, it looks like the real world and things behave like the real world," Bland said.

"It's got all of the equations to model, like how fast things accelerate due to gravity, what happens to a ball when you throw it, or how light reflecting off a pond looks."

But it's not just for video games anymore. Scientists can take the same hardware that understands how the world works and use it to make faster, more high-resolution simulations than they could with CPUs.

Titan has one GPU to each CPU inside. Summit will contain six GPUs to every three CPUs within the computer.

"Many of these projects we are doing today on Titan, but you can't get all of the science you would like to be able to do out of them," Bland said. "We find all kinds of new science by using much higher resolutions."

For example, when ORNL scientists used supercomputing to simulate the exploding star Bland mentioned, the higher resolution helped scientists understand phenomena they had been seeing for decades, but could not explain.

"You can understand effects that would never show up," Bland said. "In the past, they would do a simulation of a star exploding in two dimensions. They would just treat it as a big circle, and just assume that, as a sphere, it would be symmetric all the way around.

"For the first time, we were able to do a simulation of a star exploding in three dimensions and we found that it wasn't symmetric all the way around. When a star starts collapsing in on itself and then explodes out, you've got these rolling and tumbling things."

Getting hot

But when a computer model advances from two to three dimensions, it increases the number of calculations the computer needs to make exponentially, and it needs to make them fast.

Concerning speed, Titan is able to make about 27 quadrillion calculations per second, measured as 27 petaflops. Summit will expand that capability to around 200 petaflops.

But all of that power means Summit will use more energy and generate more heat than its predecessors. In fact, Bland said, Summit will produce more heat per square centimeter than tiles on the bottom of a spaceship re-entering Earth's atmosphere.

So in lieu of a fan — like the one you might hear whirring away inside your home computer — Summit will be cooled by water pumped through plates that sit on top of the computer's chips.

"You need a way of getting all that heat out of there, or else it's just going to melt," Bland said. "Water is a better coolant than air."

The water is funneled out as the chips heat it up. Then the water is cooled back down to room temperature and funneled back through in a closed loop, sort of like a radiator.

In all, Summit will use up to 15 megawatts, equivalent to the power 9,000 to 18,000 homes would consume, depending on the time of day. At peak, Titan uses about 9 megawatts, according to ORNL.

Titan will remain online for a little while during the transition to Summit. Bland estimates that at peak, the computers will use a combined 18 megawatts during the transition.

Generations

Summit, or as much of it as exists right now, has its own room at the Oak Ridge Leadership Computing Facility, just off the main room where its big brother Titan resides now.

"Big" really only pertains to age, though. Summit will be larger than Titan. Once Titan is decommissioned, ORNL will either put it up for excess auction or send the supercomputer back to its manufacturer, Cray.

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Titan's room will then be prepared to house the nation's first exascale computer, which will likely be bigger than both before it.

And though the supercomputers get larger, Bland, who has been at the laboratory since 1984, said it's not uncommon for them to get smaller, either.

He has seen around 30 supercomputers come and go. The first one he remembers, built in 1985, took up about the same amount of space as the office he works in now, but only made about 180 million calculations per second.

iPhones on the market today are about 10 times as powerful and can fit in a jeans pocket.

Computer technology moves quickly, and the fastest computers now will ultimately be trumped by the fastest computers built in the future.

"Summit will come in 2017, Titan came in 2012. Just five years of newer electronics make Summit that much more powerful," Bland said.

And the yet-unnamed exascale computer ORNL hopes to build by 2021 will be 50 times faster than the fastest supercomputer in use today.