Figure 3From: Systematic benchmark of substructure search in molecular graphs - From Ullmann to VF2Refinement of Ullmann algorithm. Ullmann refinement step. For a mapping of node i to atom j, all adjacent nodes x must have at least one valid mapping y. If this condition is not fulfilled, the mapping (i,j) is invalid and the corresponding matrix entry at (i,j) is set to zero.Back to article page