Fertility: We also add a fertility model P θ f ert to the translation model using the formula: where, P 0 represents the base distribution (which is set to uniform) in a Chinese Restaurant Process (CRP) 1 for the fertility model and C −i represents the count of events occurring in the history excluding the observation at position i. φ i is the number of source words aligned to (i.e., generated by) the target word e i .
this makes the complexity far worse (in practice) since the dimensionality of the feature vectors d is a much higher value than |V e |.