The BiConjugate Gradient Stabilized method (Bi-CGSTAB) was developed to solve nonsymmetric linear systems while avoiding the often irregular convergence patterns of the Conjugate Gradient Squared method (see Van der Vorst [207]). Instead of computing the CGS sequence , Bi-CGSTAB computes where is an th degree polynomial describing a steepest descent update.

**Figure:** The Preconditioned BiConjugate Gradient Stabilized Method

Mon Nov 20 08:52:54 EST 1995