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Massively Parallel, Three-Dimensional Transport Solutions for the k-Eigenvalue Problem

Gregory G. Davidson, Thomas M. Evans, Joshua J. Jarrell, Steven P. Hamilton, Tara M. Pandya, Rachel N. Slaybaugh

Nuclear Science and Engineering / Volume 177 / Number 2 / June 2014 / Pages 111-125

Technical Paper /

We have implemented a new multilevel parallel decomposition in the Denovo discrete ordinates radiation transport code. In concert with Krylov subspace iterative solvers, the multilevel decomposition allows concurrency over energy in addition to space-angle, enabling scalability beyond the limits imposed by the traditional Koch-Baker-Alcouffe (KBA) space-angle partitioning. Furthermore, a new Arnoldi-based k-eigenvalue solver has been implemented. The added phase-space concurrency combined with the high-performance Krylov and Arnoldi solvers has enabled weak scaling to O(105) cores on the Titan XK7 supercomputer. The multilevel decomposition provides a mechanism for scaling to exascale computing and beyond.