For this type of thing I've had much better results with LDA in the python package gensim. It is less prone to mis-matches based on similar keywords (since it i

For this type of thing I've had much better results with LDA in the python package gensim. It is less prone to mis-matches based on similar keywords (since it is context based) the problem with LDA is that for it to be most effective you need to have a taxonomy available for the documents, but you might be able to build a corpus or two out of sites like stack overflow.