title: Fastest Count Vectorizer Implementation
body: <p>I'm looking for an implementation of n-grams count vectorization that is more efficient than scikit-learn's <code>CountVectorizer</code>.  I've identified the <code>CountVectorizer.transform()</code> call as a huge bottleneck in a bit of software, and can dramatically increase model throughput if we're able to make this part of the pipeline more efficient.  Fit time is not important, we're only concerned with transform time.  The end output must be a <code>scipy.sparse</code> vector.  If anyone has any leads for potential alternatives it would be much appreciated.</p>