Amplification factor of the matter power spectra from simulations of 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 amplification factor B_P = P/P_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.