Solving a Model with the MLFMM To solve a model with the multilevel fast multipole method (MLFMM), you must activate MLFMM for the model. On the Solve/Run tab, in the Solution Settings group, click the Solver Settings icon. On the Solver settings dialog, click the MLFMM / ACA tab. Click Solve model with the multilevel fast multipole method (MLFMM). Figure 1. The Solver Settings dialog (MLFMM / ACA tab). Click OK to close the dialog.