The most computationally intensive computer program ever
developed has been put to work simulating the quantum behaviour
of atoms. The simulations help scientists at the US government's
Department of Energy determine the reliability of the country's
ageing stockpile of nuclear weapons without actually detonating
the weapons. The program, called Qbox, runs on the world's most
powerful supercomputer, Blue Gene/L, built by IBM and installed
at Lawrence Livermore National Laboratory in California, US. It
performs very complex quantum calculations to simulate the
behaviour of thousands of atoms in three dimensions. Researchers
at Lawrence Livermore and IBM fine-tuned Qbox to make the most
of Blue Gene/L's number-crunching abilities. They rewrote key
parts of the program to let the supercomputer's processors
tackle the relevant equations more efficiently. "The programmers
spent a lot of time finding out where the critical routines were
and how to distribute them across Blue Gene," says Jim Sexton, a
member of the r