Preconditioned iterative solution of scattering from rough surfaces

Extensions to the functionally identical forward-backward (FB) and method of ordered multiple interactions iterative techniques have been introduced that improve the convergence characteristics with specific scattering geometries. These extensions are shown to be mathematically equivalent to applying preconditioners to the discretized integral equation that is iteratively solved. The same preconditioners can be used with any iterative solution technique. Numerical examples show that the generalized minimal residual (GMRES) and bi-conjugate gradient-stable (BICGSTAB) algorithms give similarly rapid convergence when applied to a preconditioned discretized integral equation.