Comparison of MGR and GRAPPA (four genomes). We start from an unrooted tree with four leaves and select one of the two internal nodes to be the identity permutation 1 2 … n (n = 30 and n = 100). We then perform k reversals on each branch of the tree to obtain the genomes G ₁,G ₂, G ₃, and G ₄as the four leaves of the tree. The simulations were repeated 10 times for every ratio #reversals/#markers = 5k/n. (a) and (b) show the average difference between the number of reversals on the tree recovered by the algorithm and the number of reversals on the actual tree (equal to 5k). (c) and (d) show the average reversal distance between the best (i.e., closest) internal node in the solution recovered and the identity permutation.