Power spectrum boost from f (R) gravity w.r.t. to the Newtonian case. Blue and orange lines refer respectively to multigrid and FFT Poisson solvers with PySCo (in any case, the scalaron field equation is solved with non-linear multigrid), while black lines show the e-MANTIS emulator. In dotted, dashed and solid lines we use n_cells = 512³, 1024³ and 2048³. Top, middle and bottom panels have the values |f_R0| = 10^–4, 10^–5 and 10^–6. In any case we use a seven-point gradient operator.