Increase in the cumulative halo mass function from simulations for the two f(R) scenarios, ${\overline{f}}_{,R0}={10}^{-5}$ (F5, top row) and ${\overline{f}}_{,R0}={10}^{-6}$ (F6, bottom row), relative to the reference ACDM cosmology. The enhancement factor B_n = n/n_ACDM is measured for different codes (different line styles) at two different redshifts, z = 1 (left panels) and z = 0.667 (right panels). The bottom panel of each plot shows the relative agreement of the individual measurements, using MG–Arepo as a common reference.