ON SQUARING KRYLOV SUBSPACE ITERATIVE METHODS FOR NONSYMMETRIC LINEAR SYSTEMS

Abstract. The Biorthogonal Lanczos and the Biconjugate Gradients methods have been proposed as iterative methods to approximate the solution of nonsymmetric and indefinite linear systems. Sonneveld [19] obtained the Conjugate Gradient Squared by squaring the matrix polynomials of the Biconjugate Gra dients method. Here we square the Biorthogonal Lanczos, the Biconjugate Residual and the Biconjugate Orthodir(2) methods. We make theoretical and experimental comparisons