Sum factorization of the static condensed Helmholtz equation in a three-dimensional spectral element discretization

We propose a factorization technique for the Helmholtz operator of a static condensed, three-dimensional, cartesian spectral-element discretization, that yields linear complexity in the number of degrees of freedom. We then compare its performance to a reference implementation of the conventional, unfactorized approach. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)