how to evaluate lda2vec model performance

[YWP-2019]

As we know, Plexity can evaluate lda model performance.
What about lda2vec? Is there any code can be referenced?
thanks!

[JennieGerhardt]

why the loss is not reduce during training?

[leyuan]

@wp-y in the paper, the author uses NPMI (normalized pointwise mutual information) also known as coherence score (C_v).