Algebraic Schwarz preconditioning for the Schur complement: application to the time-harmonic Maxwell equations discretized by a discontinuous Galerkin method
Résumé
we primary study parallel algebraic additive Schwarz preconditioning technique for the Schur complement in the context of frequency domain electromagnetic wave propagation problems. For that purpose, the system of 2D and 3D time-harmonic Maxwell equations in first order (or mixed) form is discretized using a discontinuous Galerkin method formulated on an unstructured tetrahedral mesh. The resulting large sparse non-Hermitian complex coefficient linear system is solved by a parallel algebraic domain decomposition. More precisely, we will consider numerical techniques based on a non-overlapping decomposition of the graph associated with the sparse matrix to solve a condensed system. Although the Schur complement system is usually more tractable than the original problem by an iterative Krylov subspace technique, preconditioning treatment is still required. The numerical and parallel performance of different variants of algebraic Additive Schwarz parallel preconditioners for the Schur complement will be illustrated on a set of test problems. Furthermore, preliminary comparisons of this purely algebraic approach with continuous discrete Schwarz approach will be presented.