A class of constraint preconditioners for nonsymmetric saddle point matrices

We consider the use of a class of constraint preconditioners for the application of the Krylov subspace iterative method to the solution of large nonsymmetric, indefinite linear systems. The eigensolution distribution of the preconditioned matrix is determined and the convergence behavior of a Krylov subspace method such as GMRES is described. The choices of the parameter matrices and the implementation of the preconditioning step are discussed. Numerical experiments are presented. This work is supported by NSFC Projects 10171021 and 10471027.