After the α 1 -group, we group cells with increasing numbers based on the observation that N GLST decreases with distance, and the rate of change also decreases (Fig. ). We group them in powers of 2. Since the number of cells in the simulation box may not fit exactly in this way, after any grouping, if the number of remaining cells are less than the next power of 2, we combine them with the current group and divide them into two groups in increasing number of cells. For example, 5 non-neighboring cells are grouped into {1, 2, 2 ¯}, 10 cells into {1, 2, 3 ¯, 4 ¯}, and 20 cells into {1, 2, 4, 6 ¯, 7 ¯}, and so on. Here, the numbers with underlines denote grouping not in powers of 2.