title: Lucene ranking - how to use new 4.0 scoring models
body: <p>desperately trying to implement a new feature in the Lucene, I'm turning to you.
  Basically some additional scoring models have been added to the Lucene in this JIRA isse: <a href="https://issues.apache.org/jira/browse/LUCENE-2959" rel="nofollow">https://issues.apache.org/jira/browse/LUCENE-2959</a></p>
  
  <p>Pardon my ignorance, but I really don't understand how to get that "version" of the lucene as described in that link, so that I can use it for my own needs. The authors in that link mention that they've implemented new ranking models such as BM25, but I don't know where to get the source code, nor how to implement or run the Lucene with these new functionalities. If you have knowhow on this, your help will be highly appreciated.</p>
  
  <p>thanks in advance,</p>
  
  <p>Nik</p>