QED on the connection machine

Physicists believe that the world is described in terms of gauge theories. A popular technique for investigating these theories is to discretize them onto a lattice and simulate numerically by a computer, yielding so-called lattice gauge theory. Such computations require at least 1014 floating-point operations, necessitating the use of advanced architecture supercomputers such as the Connection Machine made by Thinking Machines Corporation. Currently the most important gauge theory to be solved is that describing the sub-nuclear world of high energy physics: Quantum Chromo-dynamics (QCD). The simplest example of a gauge theory is Quantum Electro-dynamics (QED), the theory which describes the interaction of electrons and photons. Simulation of QCD requires computer software very similar to that for the simpler QED problem. Our current QED code achieves a computational rate of 1.6 million lattice site updates per second for a Monte Carlo algorithm, and 7.4 million site updates per second for a microcanonical algorithm. The estimated performance for a Monte Carlo QCD code is 200,000 site updates per second (or 5.6 Gflops/sec).