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	SCHEDULE: NOV 11-17, 2006 Parallel I/O Advancements in Air Quality Modeling Systems Session: Poster Reception Event Type: Poster Time: 5:15pm - 7:15pm Author(s): Todd Kordenbrock, Ron Oldfield, Jeffrey Young Location: Ballroom Corridor Abstract: This poster presents an overview of and the performance results of recent I/O advancements in the parallel CMAQ framework. These optimizations were developed as part of a collaboration between the EPA and Sandia National Laboratories. netCDF provides a portable file format and an easily understood API, but it does not support concurrent writes by multiple processes. In a cluster environment, this leaves two basic options: create a file per process or funnel all the data through a single node. Neither of these options are optimal. Using a slightly modified API, parallel-netCDF (pnetCDF) enables high performance parallel I/O using the MPI-IO collective I/O optimizations while maintaining the netCDF file format. We have created a thin wrapper around pnetCDF that makes it simple for users to enable the new parallel I/O features at compile time. Using parallel I/O has improved the write performance of the CMAQ air-quality modeling code by up to 48%. Chair/Author Details: Todd Kordenbrock Sandia National Laboratories Ron Oldfield Sandia National Laboratories Jeffrey Young National Oceanic and Atmospheric Administration
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