Provably Optimal Parallel Transport Sweeps on Semi-Structured Grids
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abstract
We have found provably optimal algorithms for full-domain discrete-ordinate transport sweeps on regular grids in 3D Cartesian geometry. We describe these algorithms and sketch a "proof that they always execute the full eight-octant sweep in the minimum possible number of stages for a given P x Py Pz partitioning. Computational results demonstrate that our optimal scheduling algorithms execute sweeps in the minimum possible stage count. Observed parallel efficiencies agree well with our performance model. An older version of our PDT transport code achieves almost 80% parallel efficiency on 131,072 cores, on a weak-scaling problem with only one energy group, 80 directions, and 4096 cells/core. A newer version is less efficient at present-we are still improving its implementation - but achieves almost 60% parallel efficiency on 393,216 cores. These results conclusively demonstrate that sweeps can perform with high efficiency on core counts approaching 106.
Adams, M. P., Adams, M. L., Hawkins, W. D., Smith, T., Rauchwerger, L., Amato, N. M., ... Brown, P.
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Adams, Michael P||Adams, Marvin L||Hawkins, W Daryl||Smith, Timmie||Rauchwerger, Lawrence||Amato, Nancy M||Bailey, Teresa S||Falgout, Robert D||Kunen, Adam||Brown, Peter
