Collaborative Research: Advanced Parallel Computing Techniques with Applications to Computational Cosmology

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This project is advancing the state of art in both computational cosmology and parallel computing simultaneously and synergetically. Breakthroughs in cosmology, which improve our understanding of the formation of galaxies and planets, are enabled by advances in parallel computing being made in this project. Parallel machines with over hundred thousand powerful processors are now being built. NSF's widely accessible TeraScale facilities have already deployed a 3,000 processor machine in 2001. At the same time algorithmic advances have made it possible to solve problems at a much faster rate. Yet the complexity of algorithms combined with the difficulty of parallelizing them on such large machines remains a hindrance to advances in Science and Engineering. This project explores an object based methodology that is simplifying the process of developing highly efficient parallel applications. This approach allows users to write applications at the level of natural entities in the application domain, without explicit regard to which processors will house such entities andcarry out associated computations. To make this possible, the "runtime system" must be able to make fine-grained resource allocation decisions automatically. Advances in parallel computing are being sought to that end. Specifically, application developers may specify a program in terms of a collection of millions of objects that communicate with each other in several stylized patterns. In addition, parallel components can be plugged in and out of running computations, and exchange data with each other in a exible manner. Based on this infrastructure, this project is building a framework that makes it easy to build "particle-oriented" parallel programs. In addition to computational cosmology, which predomi-nately involves simulations that represent galaxies, dark matter, stars, planetary bodies and gas as particles, such programs are used in other fields as well. The framework contains highly efficient parallel algorithms that operate on collections of billions of particles, spread across machines with tens of thousands of processors. These advances are being used to carry out scientific studies in cosmology. Large, detailed simulations of structure formation powered by parallel computers are necessary to make quantitative predictions from cosmological theories. By calculating the non-linear gravitational and gas dynamics of the formation of galaxies and clusters of galaxies, we are creating galaxy catalogues, X-ray maps, and other observables that can be compared directly with new satellite and ground-based data, and thereby constrain the parameters of cosmological theories. These parameters include the amount and nature of the dark matter, the existence and equation of state of any dark energy, the total amount of baryons, and the nature of the initial uctuations in the Universe. Similar simulation studies are being used to study how planets form from a proto-solar disk in order to create an ab initio theory of planet formation. The software developed via this project is being made available to a wide community of researchers. Also, the research results of simulations can be downloaded or visualized via the web.