For variables that we prefer to be binary but have softened to continuous variables using sparse Beta or Dirichlet priors, we can straightforwardly strengthen the preference to be binary by modifying the objective function to favor the prior more heavily.
under a Dirichlet(ρ<1) prior we will introduce a scaling parameter τ t ≥ 1 to the prior log likelihood: τ t log P (β) with partial derivative τ t ρ−1 β kc , which adds extra weight to the sparse Dirichlet prior in the objective.