computational needs can be put forward by climate and weather modelers, computational materials scientists, and biologists, for example. In the summer of 1998, NSF and DOE sponsored the "National Workshop on Advanced Scientific Computing," which described the opportunities that this level of computing power would create for the research programs funded by NSF and DOE.2 The good news is that, as a result of the enormous investment that ASCI is making in these machines, it is likely that computers of this power will become available to the general scientific community, and at substantially reduced cost.
The ASCI program is a direct result of President Clinton's vision, a vision shared by Congress as well, that the United States can ensure the safety and reliability of its nuclear stockpile without additional nuclear testing. DOE's ASCI program has been designed to create the leading-edge computational modeling and simulation capabilities that are needed to shift from a nuclear test-based approach to a computational simulation-based approach. There is some urgency to putting this simulation capability in place as the nuclear arsenal is getting older day by day—the last nuclear test was carried out in 1992, so by the year 2004, 12 years will have passed since the last test. In addition, nuclear weapons are designed for a given lifetime. Over 50 percent of the weapons in the U.S. arsenal will be beyond their design lifetime by the year 2004, and there is very little experience in aging beyond the expected design life of nuclear weapons. Finally, the individuals who have expertise in nuclear testing are getting older, and, by the year 2004, about 50 percent of the personnel with first-hand test experience will have left the laboratories. The year 2004 is a watershed year for DOE's defense programs.
The Accelerated Strategic Computing Initiative is an applications-driven effort with a goal to develop reliable computational models of the physical and chemical processes involved in the design, manufacture, and degradation of nuclear weapons. Based on detailed discussions with scientists and engineers with expertise in weapons design, manufacturing, and aging and in computational physics and chemistry, a goal of simulating full-system, three-dimensional nuclear burn and safety simulation processes by the year 2004 was established. A number of intermediate, applications-based milestones were identified to mark the progress from our current simulation capabilities to full-system simulation capabilities. Before developing the three-dimensional burn code, codes must be developed to simulate casting, microstructures, aging of materials, crash fire safety, forging, welding of microstructures, and so on.
We cannot meet the above simulation needs unless computing capability progresses along with the simulation capability. To this end, the first ASCI computing system, an Intel system ("Option Red"), was installed at Sandia National Laboratories in Albuquerque in 1997. Sandia and the University of New Mexico wrote the operating system for this machine and, by 1996, it had achieved more than 1 trillion arithmetic operations per second (teraflops) while still at the factory. It also had over one-half terabyte of memory, the largest of any computing system to date. Next, "Option Blue" resulted in the acquisition of two machines: an IBM system at LLNL ("Blue Pacific") and an SGI/Cray system at LANL ("Blue Mountain"). The IBM system achieved its milestone of over 1 teraflops on an application