Second, the potentially competitive methods compared to our MG algorithms are the proposed smoothers used as solvers. Below we shall compare our smoothers SFP1, SFP2, and A-SFP when used as standalone methods with the corresponding MG(SFP1), MG(SFP2), and MG(A-SFP), which are three different MGs with the framework of Algorithm 2 but with a different selection of smoothers. We show the test results in Table 2.