Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/4677#discussion_r25206507
--- Diff: docs/mllib-ensembles.md ---
@@ -427,6 +427,17 @@ We omit some decision tree parameters since those are
covered in the [decision t
* **`algo`**: The algorithm or task (classification vs. regression) is set
using the tree [Strategy] parameter.
+#### Validation while training
+
+Gradient boosting can overfit when trained with more trees. In order to
prevent overfitting, it is useful to validate while
+training. The method runWithValidation has been provided to make use of
this option. It takes a pair of RDD's as arguments, the
+first one being the training dataset and the second being the validation
dataset.
+
+The training is stopped when the improvement in the validation error is
not more than a certain tolerance
+(supplied by the validationTol argument in BoostingStrategy). In practice,
the validation error
--- End diff --
I'd keep the backticks: ``` `validationTol` ``` (same for
BoostingStrategy). But the asterisks for bold are not needed.
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