Incomplete double-cone factorizations of centrosymmetric matrices arising in spectral methods.

We develop structure-preserving incomplete LU type factorizations for preconditioning centrosymmetric matrices and use them to numerically solve centrosymmetric and nearly centrosymmetric linear systems arising from spectral methods for partial differential equations. Our algorithm builds in part on direct solution techniques previously developed for this type of linear systems, featuring double-cone factorizations. We illustrate our findings on discretizations of model problems involving the Poisson, diffusion, Helmholtz, and biharmonic equations in one, two, and three dimensions. [ABSTRACT FROM AUTHOR]