[SPARK-13545][MLLIB][PYSPARK] Make MLlib LogisticRegressionWithLBFGS's default parameters consistent in Scala and Python

## What changes were proposed in this pull request?
* The default value of ```regParam``` of PySpark MLlib ```LogisticRegressionWithLBFGS``` should be consistent with Scala which is ```0.0```. (This is also consistent with ML ```LogisticRegression```.)
* BTW, if we use a known updater(L1 or L2) for binary classification, ```LogisticRegressionWithLBFGS``` will call the ML implementation. We should update the API doc to clarifying ```numCorrections``` will have no effect if we fall into that route.
* Make a pass for all parameters of ```LogisticRegressionWithLBFGS```, others are set properly.

cc mengxr dbtsai
## How was this patch tested?
No new tests, it should pass all current tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #11424 from yanboliang/spark-13545.

1 files changed, 5 insertions, 3 deletions

diff --git a/python/pyspark/mllib/classification.py b/python/pyspark/mllib/classification.py
index b4d54ef61b..53a0df27ca 100644
--- a/python/pyspark/mllib/classification.py
+++ b/python/pyspark/mllib/classification.py
@@ -326,7 +326,7 @@ class LogisticRegressionWithLBFGS(object):
     """
     @classmethod
     @since('1.2.0')
-    def train(cls, data, iterations=100, initialWeights=None, regParam=0.01, regType="l2",
+    def train(cls, data, iterations=100, initialWeights=None, regParam=0.0, regType="l2",
               intercept=False, corrections=10, tolerance=1e-6, validateData=True, numClasses=2):
         """
         Train a logistic regression model on the given data.
@@ -341,7 +341,7 @@ class LogisticRegressionWithLBFGS(object):
           (default: None)
         :param regParam:
           The regularizer parameter.
-          (default: 0.01)
+          (default: 0.0)
         :param regType:
           The type of regularizer used for training our model.
           Allowed values:
@@ -356,7 +356,9 @@ class LogisticRegressionWithLBFGS(object):
           (default: False)
         :param corrections:
           The number of corrections used in the LBFGS update.
-          (default: 10)
+          If a known updater is used for binary classification,
+          it calls the ml implementation and this parameter will
+          have no effect. (default: 10)
         :param tolerance:
           The convergence tolerance of iterations for L-BFGS.
           (default: 1e-6)