Experience on the parallelization of the OASIS3 coupler
Italo Epicoco, Silvia Mocavero, Giovanni Aloisio · 2010
This work describes the optimization and parallelization of the OASIS3 coupler. Performance evaluation and profiling have been carried out by means of the CMCC-MED coupled model, developed at the Euro-Mediterranean Centre for Climate Change (CMCC) and currently running on a NEC SX9 cluster. Our experiments highlighted that extrapolation (accomplished by the extrap function) and interpolation (implemented from the scriprmp function) transformations take the most time. Optimization concerned I/O operations reducing coupling time by 27%. Parallelization of OASIS3 represents a further step towards overall improvement of the whole coupled model. Our proposed parallel approach distributes fields over a pool of available processes. Each process applies coupling transformations to its assigned fields. This approach restricts parallelization level to the number of coupling fields. However, it can be fully combined with a parallelization approach considering the geographical domain distribution. Finally a quantitative comparison of the parallel coupler with the OASIS3 pseudo-parallel version is proposed.