Computational Infrastructure for Geodynamics (CIG) is a community-driven organization that advances Earth science by developing and disseminating software for geophysics and related fields.
Rayleigh is a CIG-developed code, targeted at the geodynamo, that solves the magnetohydrodynamic (MHD) equations in a rotating 3-D spherical shell under the Boussinesq and anelastic approximations. The code is pseudo-spectral in nature, meaning that all state variables are represented by a basis function expansion throughout large portions of the calculation. In Rayleigh, this expansion is carried out using spherical harmonics on spherical surfaces and Chebyshev polynomials in radius. Derivatives are calculated to very high accuracy using the properties of these basis functions. This high-accuracy, a major advantage of a pseudo-spectral approach, comes with a price, however. As the fluid system is evolved in time, Rayleigh transitions repeatedly between the spectral, basis-function configuration, where derivatives are calculated, and the physical-space configuration, where basis-functions have been summed and where nonlinear terms are calculated.
This repeated cycling between data configurations can incur significant communications overhead. Rayleigh's unique parallel design substantially mitigates this issue, enabling the efficient use of large-scale supercomputing resources, such as TACC's Stampede 2 ...
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Ryan Orvedahl, UC Davis
Nick Featherstone, Southwest Research Institute
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