High Performance Computing has seen extraordinary growth in peak performance from Megaflops to Teraflops in the past decades. This increase in performance has been accompanied by a large shift away from the original national security user base of the 1970s and 1980s to more commercially oriented applications (e.g., bioinformatics and entertainment). In addition, there has been a significant increase in the difficulty of using these systems, which is now the domain of highly specialized experts. In response to these trends the DARPA High Productivity Computing Systems (HPCS) program was established to produce a new generation of economically viable, high productivity computing systems for the national security and for the industrial user communities. The primary technical goals of the program are to produce petascale computers that can better run national security applications and are usable by a broader range of scientists and engineers. The HPCS program is fostering many technological innovations, and two of the more noteworthy include: the concept of a "flatter" memory hierarchy (to accelerate a whole new set of applications) and high level programming languages (to allow a new set of users to take advantage of petascale systems).

Beyond just producing petascale systems that are easier to use, the HPCS program has also funded a team of researchers to explore how to better measure productivity. This special double issue of CTWatch Quarterly features 17 articles on the topic written by folks who have devoted themselves to these questions for the past few years. The articles are broken down into two groups. The first group "User Productivity Challenges" consists of a series of broader and more easily accessible articles that seek to highlight the user experience with HPC Technologies and the current issues therein. The second group "System Productivity Technologies" is made up of more deeply technical articles that describe specific technologies for enhancing productivity. Although CTWQ is not a traditional technical journal and would not normally carry articles in the second group, we felt it was important to try to present a more complete and balanced picture of the HPCS Productivity effort and give it the kind of wide exposure that CTWQ's on-line publication model makes possible.

The articles deal with the question of productivity from a number of perspectives. Tools are then provided for folks who want to look at productivity from an organizational perspective, from an individual programmer perspective, or from the perspective of a hardware or software innovator. From the technology innovator's perspective I think we have provided two particularly useful tools. The HPC Challenge benchmarks developed under HPCS is a suite of benchmarks that allows hardware designers to get credit for innovating above and beyond the design space defined by the Top500 benchmark. The HPC software development measurement system developed under HPCS allows software designers to conduct detailed experiments with programmers and determine precisely where the users spend their time.

The productivity of HPC users intrinsically deals with some of the brightest people on the planet, solving very complex problems, using the most complex computers in the world. Anyone who truly wants to get insight into such a complex situation must be prepared to invest some time in the endeavor. However, I am confident that those who do will find the effort rewarding.