Topic models evaluation in Gensim

Question

I've been experimenting with LDA topic modelling using Gensim. I couldn't seem to find any topic model evaluation facility in Gensim, which could report on the perplexity of a topic model on held-out evaluation texts thus facilitates subsequent fine tuning of LDA parameters (e.g. number of topics). It would be greatly appreciated if anyone could shed some light on how I can perform topic model evaluation in Gensim. This question has also been posted on metaoptimize.

Answer 1

Found the answer on the gensim mailing list.

In short, the bound() method of LdaModel computes a lower bound on perplexity, based on a held-out corpus.