[SPARK-3443][MLLIB] update default values of tree:

Adjust the default values of decision tree, based on the memory requirement discussed in https://github.com/apache/spark/pull/2125 :

1. maxMemoryInMB: 128 -> 256
2. maxBins: 100 -> 32
3. maxDepth: 4 -> 5 (in some example code)

jkbradley

Author: Xiangrui Meng <meng@databricks.com>

Closes #2322 from mengxr/tree-defaults and squashes the following commits:

cda453a [Xiangrui Meng] fix tests
5900445 [Xiangrui Meng] update comments
8c81831 [Xiangrui Meng] update default values of tree:

1 files changed, 2 insertions, 2 deletions

diff --git a/python/pyspark/mllib/tree.py b/python/pyspark/mllib/tree.py
index a2fade61e9..ccc000ac70 100644
--- a/python/pyspark/mllib/tree.py
+++ b/python/pyspark/mllib/tree.py
@@ -138,7 +138,7 @@ class DecisionTree(object):
 
     @staticmethod
     def trainClassifier(data, numClasses, categoricalFeaturesInfo,
-                        impurity="gini", maxDepth=4, maxBins=100):
+                        impurity="gini", maxDepth=5, maxBins=32):
         """
         Train a DecisionTreeModel for classification.
 
@@ -170,7 +170,7 @@ class DecisionTree(object):
 
     @staticmethod
     def trainRegressor(data, categoricalFeaturesInfo,
-                       impurity="variance", maxDepth=4, maxBins=100):
+                       impurity="variance", maxDepth=5, maxBins=32):
         """
         Train a DecisionTreeModel for regression.