How to compute the optimal parameters of the parameterized PMHSS preconditioner?

Based on the preconditioned modified Hermitian and skew-Hermitian splitting (PMHSS) iteration method and its alternating-directional variant, a parameterized PMHSS (P2MHSS) preconditioner is proposed for a class of block two-by-two systems of linear equations. To optimize the preconditioning effect of the P2MHSS preconditioner, practical formulas for computing the optimal parameters of the P2MHSS preconditioner are derived by employing the scaled norm minimization method. Finally, we test the feasibility and the effectiveness of the P2MHSS preconditioner.