One task which can require substantial computing time in RMG is molecule comparison, which is done to identify if two molecules in RMG are the same chemical species. Part of the challenge is because RMG uses localized resonance structures to represent molecules, so simply comparing two structures may not be sufficient to determine whether or not they are the same. Instead, all of the resonance structures must be compared. Therefore, the standard approach to comparing molecules was to generate all resonance structures for the two species and comparing them to each other using graph isomorphism. To confirm that two molecules are the same, the comparison can return as soon as a matching pair of resonance structures is found. However, to confirm that two molecules are different, all combinations of resonance structures must be checked.