Fig. 4

Alignment of a pair of clusters. This figure shows how AligNet aligns two clusters which corresponds to Step 2 of our algorithm. The clusters in this example are, respectively, the first in the list of clusters of G, which are shown on the left in Fig. 3 and the seventh in the list of clusters of G^′, which are shown on the right in Fig. 3. We show in the picture all the steps needed to align the cluster of G with the cluster of G^′. From top to bottom in this figure, we can see that AligNet first aligns the centers of the clusters, which are the nodes highlighted in blue. Then, AligNet aligns the neighbors of the centers (second row). Next, AligNet aligns the neighbors of the neighbors. In each step we show in a different colour the nodes that are aligned in the present step. Notice that, in this example, there are two nodes that remain unmatched