Precon Precon Selected False Solver Solver Selected False SeqGS SeqGS Precon SeqSOR Selected False SeqSOR SeqSOR Precon SeqGS Selected False CGSolver CGSolver Solver BiCGSTABSolver LoopSolver GradientSolver Selected False BiCGSTABSolver BiCGSTABSolver Solver CGSolver LoopSolver GradientSolver Selected False LoopSolver LoopSolver Solver CGSolver BiCGSTABSolver GradientSolver Selected False GradientSolver GradientSolver Solver CGSolver BiCGSTABSolver LoopSolver Selected False pre pre= 0 6 pre + 1 3 post post= 0 6 post + 1 3 cells cells= 50 55 cells + 1 50