Figure 13.

GROMACS performance with FMM electrostatics for the 50 675 atom periodic salt water system (left) and for the 108 663 atom aerosol/multidroplet benchmark (right). Encircled numbers indicate FMM tree depth. With p = 8 as indicated by the dashed vertical line, FMM offers an accuracy of the electrostatic interactions that is comparable to the “default” PME parameter set (i.e., r_c = 1.0 nm, PME grid spacing s = 0.12 nm, fourth order interpolation, see Figure 9). Benchmarks were run with 20 OpenMP threads on the CPU.