Scaling of computational time with number of bodies. The setup is the same as in Sect. 3.1. The surface density is kept constant at 10 g cm⁻². The number of planetesimals increases from 1000 to 10 000. Shown are the total computational time to integrate 10⁴ yr with thesequential approach (sequential; orange), the group approach (grouping; blue), and, for comparison, with mercury (grey diamond). Also shown is a power-law fitting to find the scaling with N for our model (blue and orange lines).