[SPARK-4047] - Generate runtime warnings for example implementation of PageRank

Based on SPARK-2434, this PR generates runtime warnings for example implementations (Python, Scala) of PageRank.

Author: Varadharajan Mukundan <srinathsmn@gmail.com>

Closes #2894 from varadharajan/SPARK-4047 and squashes the following commits:

5f9406b [Varadharajan Mukundan] [SPARK-4047] - Point users to LogisticRegressionWithSGD and LogisticRegressionWithLBFGS instead of LogisticRegressionModel
252f595 [Varadharajan Mukundan] a. Generate runtime warnings for
05a018b [Varadharajan Mukundan] Fix PageRank implementation's package reference
5c2bf54 [Varadharajan Mukundan] [SPARK-4047] - Generate runtime warnings for example implementation of PageRank

1 files changed, 8 insertions, 0 deletions

diff --git a/examples/src/main/python/pagerank.py b/examples/src/main/python/pagerank.py
index b539c4128c..a5f25d78c1 100755
--- a/examples/src/main/python/pagerank.py
+++ b/examples/src/main/python/pagerank.py
@@ -15,6 +15,11 @@
 # limitations under the License.
 #
 
+"""
+This is an example implementation of PageRank. For more conventional use,
+Please refer to PageRank implementation provided by graphx
+"""
+
 import re
 import sys
 from operator import add
@@ -40,6 +45,9 @@ if __name__ == "__main__":
         print >> sys.stderr, "Usage: pagerank <file> <iterations>"
         exit(-1)
 
+    print >> sys.stderr,  """WARN: This is a naive implementation of PageRank and is
+          given as an example! Please refer to PageRank implementation provided by graphx"""
+
     # Initialize the spark context.
     sc = SparkContext(appName="PythonPageRank")