Record Display for the EPA National Library Catalog


OLS Field Name OLS Field Data
Main Title Optimizing a Photochemical Air Quality Model Gas-Phase Chemistry Solver for Parallel Processing.
Author Cheung, W. ; Young, J. O. ; Davis, E. W. ;
CORP Author North Carolina State Univ. at Raleigh. Dept. of Electrical and Computer Engineering.;Environmental Protection Agency, Research Triangle Park, NC. National Exposure Research Lab.
Publisher 1997
Year Published 1997
Report Number EPA-R-822076-01-2; EPA/600/A-97/017;
Stock Number PB97-192918
Additional Subjects Photochemistry ; Parallel processing(Computers) ; Computational grids ; Air pollution dispersion ; Photochemical reactions ; Environmental transport ; Euler equations of models ; Optimization ; Mathematical models ; Computerized simulation ; Algorithms ; QSSA(Quasi-Steady State Approximation) ; Air Quality Model
Internet Access
Description Access URL
Library Call Number Additional Info Location Last
NTIS  PB97-192918 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 12/22/1997
Collation 13p
In a testbed model based on EPA's Regional Oxidant Model, the Quasi-steady State Approximation (QSSA) gas-phase chemistry solver dominates the computation, which is typical of Eulerian grid cell air quality models. We report results from optimizing the testbed solver on a Cray T3D parallel system. We use a simple processor mapping to assign a block to grid cells to each T3D processing element (PE). To minimize execution time, programming optimization techniques, such as cache collision avoidance and loop unrolling, have been applied. Proper application of such techniques has a significant effect on performance, leading to improve speedup as compared with simply relying ng on optimizing compilers. PEs become idle while remaining Pes complete their tasks within a simulation time step. Based on experience with optimizing the QSSA on Cray vector supercomputers, a dynamic task allocation approach to deal with local imbalance is described and performance results are given.