rather than placing a few large bets on projects that could have an important impact.

This chapter has focused on the tangible aspects of supercomputing and the actions needed to improve them. However, one should not neglect the intangible assets of the supercomputing enterprise. Supercomputing has attracted the brightest minds and drawn broad support because of the reality as well as the perception that it is a cutting-edge, world-changing endeavor. The reality has not changed. There are difficult fundamental computer science and engineering problems that need to be solved in order to continue pushing the performance of supercomputers at the current rate. Clearly, fundamental changes will be needed in the way supercomputers are built and programmed, to overcome these problems. Supercomputers are becoming essential to research in an ever-growing range of areas; they are solving fundamental scientific problems and are key to progress on an increasing range of societal issues. Computational science is becoming an increasingly challenging intellectual pursuit as the ad hoc use of numerical recipes is replaced by a deeper understanding of the relation between the physical world and its discrete representation. The reality is there, but, arguably, the perception has dimmed. As some uses of high-performance computing become easier and more common, it becomes easier to forget the incredibly difficult and immensely important challenges of supercomputing.

Initiatives to buttress the research on supercomputing technologies and the use of supercomputers in science and engineering should address the perception as well as the reality. It is important that research programs be perceived as addressing grand challenges: The grand engineering challenge of building systems of incredible complexity that are at the forefront of computer technology and the grand scientific challenges addressed by these supercomputers. It is also important that government agencies, supercomputing centers, and the broad supercomputing community do not neglect cultivating an image they may take too much for granted.