Convergence of the halo mass function in Nyx simulations with the Reeber halo finding code. Solid lines demonstrate how Reeber’s distribution of halo masses change when increasing the spatial resolution in Nyx runs. As expected, we observe the differences only at the low-mass end, since coarse grids cannot capture well small halos, while the agreement on the high-mass end is good. The dashed lines show results of a FOF halo finder when the linking length parameter is chosen to match approximately the iso-density contour used in Reeber. FOF results are used as a validation here, showing that Reeber results converge to the ‘correct’ answer.