In addition to the model parameters, hyperparameters are re-sampled after each training iteration following the discount and strength hyperparameter resampling in a hierarchical Pitman-Yor process (Teh, 2006).
we resample ⟨d p , θ p ⟩, the pair of discount and strength parameters for phrases from a distribution: where [ ] denotes a generalized Pochhammer symbol, and c ⟨s,t⟩ the number of customers of phrase pair ⟨s, t⟩.