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 had also been posted on Stackoverflow.
This seemingly recent (and great) addition to GitHub by Markus Konrad seems to address MANY Topic Modeling evaluation problems:
tmtoolkit - Text Mining and Topic modeling tool kit: