What, Exactly, Is a Supercomputer?

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Lawrence Livermore National Laboratory

Sequoia supercomputer

It’s official: The United States is home to the world’s fastest supercomputer. But what exactly are supercomputers and why should we care about them?

I decided to go straight to the source — Mike McCoy, program director for advanced simulation and computing at Lawrence Livermore National Laboratory. He’s the man in charge of Sequoia, the record-breaking supercomputer that’s been grabbing headlines and making techies drool over the last few days. Prepare to look at your MacBook Pro in shame.

What is a supercomputer?

Exactly what it sounds like: an extremely powerful computer. Sequoia, a third-generation Blue Gene machine from IBM, runs on 1.6 million processor cores. It can reach speeds of up to 20 petaflops — a petaflop, by the way, equals 1015 operations per second, which means that Sequoia can perform 20 x 1015 operations every second.

The whole shebang requires 3,000 gallons of water per minute to cool it down. As you might imagine, it takes a lot of energy to keep this machine going, using 6 or 7 megawatts on average with peak usage approaching 9 1/2 megawatts. (One megawatt equals 1 million watts).

“That might seem like a lot, because that’s $6 or $7 million a year in power,” says McCoy, “but if we hadn’t worked closely with IBM that could have easily been north of 10 megawatts.” Those 1.6 million cores are located on 96 different racks, each of which weighs nearly 5,000 pounds and gives off an average of 100 kilowatts of energy, the amount needed to power about 50 single-family homes.

Who uses them?

Researchers. Every six months, Lawrence Livermore National Laboratory gets around 20 to 25 proposals from different national laboratories and accepts around 10 of them. At any given time there are usually one to four projects using the supercomputer. Priority is given to whatever project is deemed most important, and less intensive computer tasks are performed by smaller, less expensive computers.

Researchers aren’t booking time with Sequoia to play Minesweeper. This is some complicated stuff, ranging from research on how to implode tiny capsules of hydrogen with a laser to simulate what happens inside of the sun to modeling physical systems such as aircraft engines, Earth’s climate and the human vascular system.

Since serious policy decisions can be based on results from these calculations, they have to be extremely accurate — not an easy task when you’re talking about 1.6 million processor cores that need to communicate, synchronize and, most importantly, not break down.

“Imagine if you had to work on a million PCs every day and every one of them had to work,” says McCoy. “Chances are that one of them would fail. If your results depended on every one of them working, you wouldn’t be able to get any work done.”

How much does a supercomputer cost?

So, you’re in the market for a top-of-the-line supercomputer. Aside from the $6 to $7 million in annual energy costs, you can expect to pay anywhere from $100 million to $250 million for design and assembly, not to mention the maintenance costs.

How much faster can supercomputers get?

Why does Sequoia require 1.6 million processor cores? Because processors aren’t getting any faster.

“The laws of physics are hunting us down,” says McCoy. “One of the things that make processors work faster is increasing the frequency of the processors. We found that we can’t increase the frequency like we used to simply because the amount of heat generated would melt the computer.”

If we can’t make processors faster, we just have to add more processors, which would explain why supercomputers keep getting bigger and bigger. But is a supercomputer with 100 million cores using using 100 megawatts of energy even practical?

Probably not, which is why researchers are hoping investment in new technologies can help us eventually reach exascale levels of computing, which would mean speeds of up to 1018operations per second.

How long do these supercomputers last?

Not very long. In fact, the average supercomputer has a shorter lifespan than your average Xbox 360. “The computer will be world-class for maybe 2 or 2 ½ years,” says McCoy. “It’s a useful resource for about 5 years. Then, historically speaking, it makes no sense to keep them because the cost of maintenance and power is so much it makes more sense to go out and get a new system.”