Two supercomputers, called Q and Green Destiny, at the U.S. Energy Department’s Los Alamos National Laboratory illustrate two of the main approaches to supercomputing — raw power versus efficiency, the New York Times reported today (see GSN, April 4).

Los Alamos researchers plan to use the computing powers of Q — rated at 30 teraops, which means it can perform 30 trillion calculations per second — to conduct a full-scale replication of the physics involved in a nuclear explosion (see GSN, April 9).

“Obviously with the various treaties and rules and regulations, we can't set one of these off anymore,” said Chris Kemper, deputy leader of the Los Alamos computing, communications and networking division.  “In the past we could test in Nevada and see if theory matched reality.  Now we have do to it with simulations.”

One drawback to Q, however, is the power that it needs to run, the Times reported.  The supercomputer uses three megawatts of electricity on its own and another two megawatts to power its cooling system.  Combined, that amount of electricity is enough to power about 5,000 homes, according to the Times.

The Green Destiny supercomputer is rated at 160 gigaops, which means that it can perform only billions of operations per second.  Its advantages, however, include a lower price and greater efficiency than Q, according to the Times.  At a cost of $335,000, Green Destiny is cheaper than Q, which costs $215 million plus $93 million for housing expenses.

Green Destiny also requires much less power, the Times reported.  It only uses about five kilowatts of electricity, a thousandth of that used by Q.  Even if Green Destiny were expanded to its maximum of 30 teraops, it would still only use about one megawatt, according to the Times.

“Bigger and faster machines simply aren't good enough anymore,” said Wu-Chung Feng, leader of the Green Destiny project at Los Alamos.  The time has come to question the doctrine of “performance at any cost,” he said.

The more power a supercomputer uses leads to an increase in heat, according to the Times.  If the operating temperature is increased by 18 degrees Fahrenheit, then reliability will be reduced by half, Feng said.  Because of this, Q is expected to only be able to operate for a few hours at a time before it will need rebooting, the Times reported.

While researchers could keep on increasing the raw power of supercomputers, it could lead to greater losses of reliability and efficient power use, Feng said.

“There are two paths now for supercomputing,” he said.  “We’re not saying this is a replacement for a machine like Q but that we need to look in this direction” (George Johnson, New York Times, June 25).

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