Scalabiliity of the Leeds Dynamo Code for Geodynamo Simulations
Abstract
The Leeds Dynamo Code uses a conventional pseudospectral method in which the dependent variables are represented as toroidal and poloidal scalars expanded in spherical harmonics. Radial variations are represented by variable order, variable spacing, finite differences and time-stepping is by a predictor-corrector method. There are separate Boussinesq and anelastic versions, with options for a rotating inner core with different electrical conductivity and a laterally varying heat flux through the upper surface (core-mantle boundary). The code has already been used for several published studies of thermal core-mantle interactions, including locking of the dynamo to mantle anomalies, and planetary and astrophysical studies. The time-limiting step is the Legendre transform. Simple parallelisation is in radius, when the finite difference method allows for almost perfect scaling when the number of cores is less than the number of radial grid points. This will become a significant restriction because the number of grid points rarely exceeds a few hundred and computers with much larger numbers of cores are becoming available. A new parallelisation in colatitude as well as radius is currently being tested. The slow Legendre transform is a matrix multiplication, an n-cubed process with n-squared scalars, so the code is expected to show weak scalability (which scales well as the problem size increases with the number of cores, the relevant case). The code is running on the University of Texas machine Stampede, which is currently ranked 6th in the top 500. It is an interesting heterogeneous machine with 16 conventional cores and an Intel coprocessor with 61 cores on each node. Testing on this machine will explore the effectiveness of the coprocessor in performing the Legendre transform as a standardmatrix multiplication.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGP51A1068G
- Keywords:
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- 1510 GEOMAGNETISM AND PALEOMAGNETISM Dynamo: theories and simulations;
- 0550 COMPUTATIONAL GEOPHYSICS Model verification and validation