Number of regular grid cells to be visited for each reference cell with a side length Lcell, given a spherical range searching with the maximum distance of R_max, and a periodic box that is sufficiently large. Here, 𝔑_tot = 𝔑_inner + 𝔑_edge, where 𝔑_inner and 𝔑_edge indicate the number of cells that are fully and partially inside the query range, which correspond to the yellow and pink regions in Fig. C.1, respectively. The dashed and dotted black lines show analytical formulae that fit the numerical results in the small-cell limit well.