When the cpp token PVP is set, ordering of the complex coefficients within the arrays is along diagonals of m (zonal wavenumber), and n (total wavenumber) space. Level index "k" (not to be confused with spectral truncation parameter "K") is the slowest varying index of these arrays. Spectral space computations on a vector computer are done most efficiently with this ordering scheme because it results in the longest possible vector lengths. Arrays ncoefi, nm, and nco2 in /comspe/ define lengths and starting addresses within the various spectral arrays. A pictorial representation of the structure of the spectral space arrays is presented in Figure 3.6.
When PVP is not set, spectral data ordering is changed in order to optimize
performance on cache-based architectures, and to facilitate message-passing.
The storage arrangement in this case is depicted in Figure
3.5
Questions on these pages can be sent to... erik@ucar.edu .
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