The combinatorial problem that occurs in SMARTY is exacerbated in SMIRKY since multiple atoms may require decorators or alpha or beta substituents. It is difficult to identify a specific reason SMIRKY does not reach a 100% partial score for some of the torsion types and the five missing bond types. This suggests that the combinatorial problem described above (Section 3.2.2) is the most likely source of failure. Thus it seems likely that chemical perception sampling tools in future force field parameterization will need improved move sets with higher acceptance rates.