NERSCPowering Scientific Discovery Since 1974

NERSC Initiative for Scientific Exploration (NISE) 2011 Awards

Hybrid OpenMP/MPI approach to R-matrix scattering

Connor Balance, Auburn University

Associated NERSC Project: Computational Atomic Physics for Fusion Energy (m41)
Principle Investigator: Michael Pindzola, Auburn University

NISE Award: 600,000 Hours
Award Date: June 2011

The R-matrix/RMPS method has been employed successfully for a wide range of electron-impact excitation/ionisation cases as well as single-photon ionisation. One of the most time demanding aspects of each calculation is the formation of the R-matrix itself, which must be carried out for each incident electron/photon energy. This is effectively achieved by use of DGEMM for a user defined number of slices, with the MPI gathering and mapping the result to a global matrix. Currently, this is achieved via multi-level MPI parallelisation, but we would like to investigate an OpenMP/MPI approach. In this study, the energies of the incoming electron/photon would still be distributed over a number of nodes using MPI, but the formation of the R-matrix shall be carried out via OpenMP utilizing the cores of a particular node. It is hoped that by confining the intensive communication between cores to within an node, that this shall provide an additional speed-up our code base, allowing us to run at a higher scale in future calculations.