Parameterized rotated block preconditioning techniques for block two-by-two systems with application to complex linear systems

In this paper, based on the rotated block triangular preconditioning technique, we present a class of parameterized rotated block preconditioners to accelerate Krylov subspace iterative methods with coefficient matrices of nonsymmetric sub-blocks. The parameterized rotated block preconditioners can be seen as a generalization of the rotated block triangular preconditioners. The eigen-properties of the corresponding preconditioned matrices are analyzed. Numerical experiments are used to demonstrate the feasibility and effectiveness of the parameterized rotated block preconditioners.