scikit-learn/scikit-learn — pull request #2528 by ogrisel (2013-10-16 14:31:20+00:00)
Title: [WIP] Release the GIL at tree building time

Good news! Thanks to Gilles releasing the GIL on most splitter methods, we can now release the GIL for most of the tree construction as well.

I did a bench and I get a 10x speedup on a 12 cores machine with a python thread pool (individual trees build in 6s).