A preconditioner for the Schur complement matrix

A preconditioner for iterative solution of the interface problem in Schur Complement Domain Decomposition Methods is presented. This preconditioner is based on solving a problem in a narrow strip around the interface. It requires much less memory and computing time than classical Neumann-Neumann preconditioner and its variants, and handles correctly the flux splitting among subdomains that share the interface. The performance of this preconditioner is assessed with an analytical study of Schur complement matrix eigenvalues and several numerical experiments conducted in a sequential computational environment. Results in a production parallel finite element code are given in a companion paper [1].