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Section site map: News |
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News | |
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2005 News Stories
NewsHarnessing TeraGrid to the Sky: Understanding Dark EnergyUnderstanding dark energy, the mysterious effect that seems to counteract gravity, is one of the most pressing topics in modern cosmology. One of its consequences - known as the Integrated Sachs Wolfe (ISW) effect - is that the energy of light from the cosmic microwave background (CMB) is expected to increase (blue-shift) as it passes through large structures like galaxy clusters. Verifying and quantifying this effect requires correlating CMB data with the presence of such structures, as captured for example in the Sloan Digital Sky Survey (SDSS), the most complete survey of one quarter of the sky. A major new initiative, the National Virtual Observatory (NVO) sponsored through an NSF Information Technology Research project, has the objective of providing tools that allow researchers to explore the data at different wavelengths and extract useful scientific information. Only by collating data from multiple sources can science realize the full potential of this information. The TeraGrid will faciliatate effective use of NVO by making it possible to distribute computations transparently across diverse computers, located in different parts of the country. For example, one way of establishing errors on the ISW measurements is to generate data statistically similar to that of the CMB and analyze those as well. Many such independent tests are required, a task well suited to a large Condor pool. Some powerful TeraGrid resources, however, such as the TCS at PSC, do not have individual processors directly network accessible, a requirement for the traditional use of Condor. This problem was solved by GridShell, developed by Ed Walker and others from the Texas Advanced Computing Center. GridShell allows the processors of a massively parallel system to be directly addressed ?to act as a Condor pool ? with no system changes. It runs completely as user code. Using GridShell (and with assistance from PSC's Jeff Gardner), University of Pittsburgh cosmologists Andrew Connolly and Ryan Scranton ran tens of thousands of comparisons with data statistically similar to the CMB data. They used TeraGrid systems at PSC, TACC and NCSA. The proof of concept and development work with this application under GridShell shows that systems such as the TCS can be used in this manner. With GridShell, jobs were scheduled independently among these distributed TeraGrid systems, which appeared to the user as one large machine. 
Figure 1: CMB temperature map from the Wilkinson Microwave Anisotropy Probe |
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The TeraGrid project is funded by the National Science Foundation and includes 11 partners: Please email help@teragrid.org with questions or comments or fill out the online feedback form. |
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