“…However, the first estimation step poses significant challenges as it boils down to a hard density regression problem (Dunson et al,
2007). For example, to estimate
(or equivalently
), a line of works (Deb et al,
2021; Scott et al,
2015; Tansey et al,
2018) proceeds by assuming a fixed alternative density, i.e.
to make way for the application of an EM algorithm.…”