A high resolution parallel Legendre transform algorithm
The spectral weather forecasting model at ECMWF is a sophisticated parallel program which uses global memory for the large shared data structure which contains the spectral representation of the atmosphere. In this paper the structure of this model is described and the section of the program which updates and references the shared spectral data structure is isolated. This extract, the Legendre transforms, contains all the critical parallel structure in the model. These transform algorithms are described and their relative performance on the Cray X-MP and the ETA 10 is presented.
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