Top panel: ratio of the power spectrum for three-, five- and seven-point gradient in blue, orange and green lines respectively using multigrid, with respect to RAMSES (with AMR disabled and also using multigrid). Because RAMSES does not stop exactly at z = 0 we rescaled its power spectrum the linear growth factor. The grey shaded area show the ±1% limits. Bottom panel: ratio of the power spectrum using the PySCo FFT_7pt solver w.r.t PySCo multigrid. The dark grey shaded area show the 10^–5 limits. In any case we use a TSC algorithm.