The US military's Roadrunner supercomputer has become the first machine to calculate at more than a quadrillion (1015) operations per second, thereby crossing the petaflop barrier.

The record was technically set on 25 May, in IBM's laboratories in Poughkeepsie, New York, using the LINPACK standard benchmark for comparing supercomputer performance. In early June, however, it achieved petaflop performance on a real-life application of modelling the human cortex, says David Turek, vice-president for 'deep computing' at IBM.

It thus beats the record of IBM's Blue Gene/L machine, based at the Lawrence Livermore National Laboratory in California, which managed about 500 teraflops (1012).

Roadrunner was built to run calculations to ensure the safety of the US nuclear stockpile, and is due to be delivered next month to the Los Alamos National Laboratory in New Mexico for that purpose. In the meantime, it will also run other calculations, including plasma physics, molecular dynamics and climate change.