199-Excitation Tests. We next consider the performance of λAPC-tPBE on the entire set of 199 excitations in the QUESTDB database that meet the selection criteria criteria of section 2.3. For this larger test, we used only four values of λ (i.e., N trial = 4) to generate active spaces: λ = 0.25, 0.5, 0.75, and 1.25. These values of λ were chosen based on their good performance on the 30-excitation tests (see the Supporting Information for more discussion of this point).