A Simple Approach to Enhance I/O Performance in the WRF-CMAQ Two-Way Coupled Model
The I/O scheme in the current model does not make use of any parallel file system or parallel I/O approach. In addition, the I/O takes about 15% - 28% of the entire simulation. The new approach not only utilizes parallel I/O capability offerred by pnetCDF or netCDF4 but goes one step further to aggregate the data locally, i.e. along column dimension or row dimension among MPI processes in the spatial domain. This approach not only reduces the I/O traffic contention but also aggregated data enhances the I/O efficiency. In terms of I/O time, we have shown this method is about 6 to 10 times faster than the current existing I/O scheme in the model and about 20% - 3 times faster than strict application of pnetCDF. We are currently testing the same idea with netCDF4.