Different approaches to computing document similarity, compared quantitatively using the Reuters-21578 corpus. This blog post has more details:

Document Similarity using various Text Vectorizing Strategies

• Make a data folder under the project directory.
• Download and expand the Reuters-21578 corpus into this folder. This will create a data/reuters-21578 folder under the project directory.
• Run the parse-input.py script, this will parse the corpus data and produce two flat files, one for text and another for tags in the data directory, called text.tsv and tags.tsv respectively.
• Generate vectors for the tags by running the tag-sims.py script. This will generate a tag-vecs.tsv file in the data directory.
• Generate vectors for a vectorizer by running one of the *-sims.py scripts, which will generate a corresponding *-vecs.csv or *-vecs.mtx file depending on whether the generated vectors are dense or sparse.
• Compute the correlation coefficient between the tag vectors and the text vectors by running the calc-pearson.py script.