Distributions of cross-match (orange) vs. training-set (blue) sources of RRAB type in the sky (panel a), in Galactic coordinates (degrees), and in the G-band magnitude (panel b). The source sampling helped reduce the number of sources for training and smoothed both magnitude and sky distributions (with intended over-densities in the regions of the Galactic bulge and Magellanic Clouds), while semi-supervised sources filled the under-represented region in the cross match centred around the Galactic longitude of 300°.