Chempy abundance predictions (for the medians of the marginalized posterior PDFs, ), compared to the observed stellar abundances. The top row compares the predicted (red, green) and observed (blue) abundances for the Sun, after optimizing for Sun+ constraints; the central panel shows an analogous comparison for the B-stars, and the bottom panel for Arcturus. Predictions for the default yield set are shown in green; for the alternate yield set in red. The log likelihood coming from each individual element as well as the sum of all are indicated. In general, the default and alternate yield sets fit comparably well (or poorly). The predictions for some elements, for example, Na, K, Ti, and V are poor, for both yield sets and for Sun+ and Arcturus+. This implies that some abundances simply cannot be reproduced in the context of GCE models, even if a model as flexible as Chempy is applied.