Two-level additive Schwarz preconditioners for P1 nonconforming finite elements for nonsymmetric and indefinite problems

摘要

Two-level additive Schwarz preconditioners are developed for P1 nonconforming finite element approximation of second-order nonsymmetric and indefinite elliptic problems. The convergence factor is shown to be independent of the number of subspaces when this preconditioner is used with GMRES method.