Effect of the number of bins per component N on the wall-clock time T (top panels) and the wall-clock time per step T_{per step} (bottom panels) for the adaptive time step. From the left, the panels show the results for the (a) one-component constant kernel, (b) one-component additive kernel, (c) two-component constant kernel, and (d) two-component additive kernel. In each plot, different colors correspond to the direct method, or the different values of θ_c for the tree methods. The tree method was calculated with k_c = 1 000 000. The lines were fit by the least squares method, using the logarithmic values of N and T.