For example, the neural variational document model (NVDM;Miao et al., 2016) allows θ i ∈ R K and achieves normalization by taking the softmax of θ i B.
the experiments in Srivastava and Sutton (2017) found the performance of the NVDM to be slightly worse than LDA in terms of perplexity, and dramatically worse in terms of topic coherence.