Initialisation- (orange) and simulation runtime (blue) vs. particle count N, as in Fig. 4. Dashed lines are guidelines with slopes of 1, 2, and 3. The initialization time is respectively linear and quadratic in N for N < 1/є and N > 1/є, in accordance with the estimates in Table 2. However, because only mergers were simulated, there were at most N collisions, which results in a runtime of O(N³) instead of O(N⁴).