The last time the country was in a similar position was three years ago. The fastest machine - Titan, at Oak Ridge National Laboratory in Tennessee - is an upgrade of Jaguar, the system which held the top spot in 2009.
The supercomputer will be used to help develop more energy-efficient engines for vehicles, model climate change and research biofuels. It can also be rented to third-parties, and is operated as part of the US Department of Energy's network of research labs.
The Top 500 list of supercomputers was published by Hans Muer, professor of computer science at Mannheim, who has been keeping track of developments since 1986. It was released at the SC12 supercomputing conference in Salt Lake City, Utah.
Titan leapfrogged the previous champion IBM's Sequoia - which is used to carry out simulations to help extend the life of nuclear weapons - thanks to its mix of central processing unit (CPU) and graphics processing unit (GPU) technologies.
According to the Linpack benchmark it operates at 17.59 petaflop/sec - the equivalent of 17,590 trillion calculations per second. GPU processors are designed to carry out hundreds of calculations in parallel The benchmark measures real-world performance - but in theory the machine can boost that to a "peak performance" of more than 20 petaflop/sec.
Source: BBC News
