New preconditioner strategy for solving block four-by-four linear systems: An application to the saddle-point problem from 3D Stokes equation

We have presented a fast method for solving a specific type of block four-by-four saddlepoint problem arising from the finite element discretization of the generalized 3D Stokes problem. We analyze the eigenvalue distribution and the eigenvectors of the preconditioned matrix. Furthermore, we suggested utilizing the preconditioned global conjugate gradient method (PGCG) as a block iterative solver for handling multiple right-hand sides within the sub-system and give some new convergence results. Numerical experiments have shown that our preconditioned iterative approach is very efficient for solving the 3D Stokes problem