  We introduce an algorithm that is able to find the facets of Coulomb diamonds
in quantum dot arrays. We simulate these arrays using the constant-interaction
model, and rely only on one-dimensional raster scans (rays) to learn a model of
the device using regularized maximum likelihood estimation. This allows us to
determine, for a given charge state of the device, which transitions exist and
what the compensated gate voltages for these are. For smaller devices the
simulator can also be used to compute the exact boundaries of the Coulomb
diamonds, which we use to assess that our algorithm correctly finds the vast
majority of transitions with high precision.
