A note on constraint preconditioners for nonsymmetric saddle point problems

Abstract

AbstractA class of constraint preconditioners for solving two‐by‐two block linear equations with the (1,2)‐block being the transpose of the (2,1)‐block and the (2,2)‐block being zero was investigated in a recent paper of Cao (Numer. Math. 2006; 103:47–61). In this short note, we extend his idea by allowing the (1,2)‐block to be not equal to the transpose of the (2,1)‐block. Results concerning the spectrum, the form of the eigenvectors and the convergence behaviour of a Krylov subspace method, such as GMRES are presented. Copyright © 2007 John Wiley & Sons, Ltd.