We discuss the scaling behavior of a state-of-the-art Configuration Interaction code for nuclear physics on modern multicore computer architectures. In the CI approach, the quantum many-body problem is expressed as a large sparse symmetric eigenvalue problem, of which the lowest eigenvalues and eigenvectors have to be computed. We compare the performance of the pure MPI version with the hybrid MPI/OpenMP code on Cray XT4 and XT5 platforms. For large core counts (typically 5,000 and above), the hybrid version is more efficient than pure MPI.
Pieter Maris, Masha Sosonkina, James P. Vary, Esmo