Relative error in potential and forces for both the HO (left) and the CylSP methods (right) for the prolate models with a different c/a at r = 0.01. Left panels: the red, blue, and green lines are the results for the HO method with (n_max, l_max) = (16,12), (12,12), and (6,4), respectively. Right panels: the red, blue, and green lines represent the results for the CylSP method with R_min = 0.1, 0.01, and the value given by AGAMA, respectively. From top to bottom: the radius r is along the x-, x-, y-, and z-axes, respectively.