scikit-learn/scikit-learn — pull request #1806 by yanirs (2013-03-24 03:56:39+00:00)
Title: Addressing issue #1802 (Gradient Boosting Out-of-bag Estimates)

Changed oob_score_ to be calculated based only on trees where the OOB instances weren't used for training.
Not entirely sure about the correctness of doing it this way, but it seems to make the OOB scores more reliable (based on local testing).