Each distinct structure at the DFT level is put in a separate 'bin'. The bins test, Δabins, is a measure of how well the priority list avoids prioritizing duplicate conformers. The 150 molecules in the DFT dataset have 15342 conformers at FF level. In the 15342 re-optimization calculations at the DFT level, 2280 (or 14.9%) did not lead to a unique structure. There are 13062 unique structures, thus 13062 bins, in the complete dataset. The number of populated bins for a particular selection of conformers from partial optimizations divided by the total number of distinct structures at the DFT level is labelled rbins (Figure ). A plot of rbins vs ropt plot (Figure .B) shows how rbins increases with ropt, the fraction of the total number of structures that has been re-optimized. For the optimal order, rbins should increase linearly with ropt and plateau at rbins = 1. The plot of rbins vs ropt for a proposed priority list is always under the line of the DFT list. The bins test, Δabins, is the area between the optimal order and the actual result in a rbins vs ropt plot. A proposed priority list with a small Δabins value is desirable as conformers with unique structures are prioritized and duplicate conformers are avoided like in the DFT list. CONFPASS tries to minimize Δabins.