[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

examples/src/main/java/org/apache/spark/examples/JavaHdfsLR.java

@@ -30,12 +30,25 @@ import java.util.regex.Pattern;
 
 /**
  * Logistic regression based classification.
+ *
+ * This is an example implementation for learning how to use Spark. For more conventional use,
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 public final class JavaHdfsLR {
 
   private static final int D = 10;   // Number of dimensions
   private static final Random rand = new Random(42);
 
+  static void showWarning() {
+    String warning = "WARN: This is a naive implementation of Logistic Regression " +
+            "and is given as an example!\n" +
+            "Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD " +
+            "or org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS " +
+            "for more conventional use.";
+    System.err.println(warning);
+  }
+
   static class DataPoint implements Serializable {
     DataPoint(double[] x, double y) {
       this.x = x;
@@ -109,6 +122,8 @@ public final class JavaHdfsLR {
       System.exit(1);
     }
 
+    showWarning();
+
     SparkConf sparkConf = new SparkConf().setAppName("JavaHdfsLR");
     JavaSparkContext sc = new JavaSparkContext(sparkConf);
     JavaRDD<String> lines = sc.textFile(args[0]);

examples/src/main/java/org/apache/spark/examples/JavaPageRank.java

@@ -45,10 +45,21 @@ import java.util.regex.Pattern;
  * URL         neighbor URL
  * ...
  * where URL and their neighbors are separated by space(s).
+ *
+ * This is an example implementation for learning how to use Spark. For more conventional use,
+ * please refer to org.apache.spark.graphx.lib.PageRank
  */
 public final class JavaPageRank {
   private static final Pattern SPACES = Pattern.compile("\\s+");
 
+  static void showWarning() {
+    String warning = "WARN: This is a naive implementation of PageRank " +
+            "and is given as an example! \n" +
+            "Please use the PageRank implementation found in " +
+            "org.apache.spark.graphx.lib.PageRank for more conventional use.";
+    System.err.println(warning);
+  }
+
   private static class Sum implements Function2<Double, Double, Double> {
     @Override
     public Double call(Double a, Double b) {
@@ -62,6 +73,8 @@ public final class JavaPageRank {
       System.exit(1);
     }
 
+    showWarning();
+
     SparkConf sparkConf = new SparkConf().setAppName("JavaPageRank");
     JavaSparkContext ctx = new JavaSparkContext(sparkConf);
 

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")
 

examples/src/main/scala/org/apache/spark/examples/LocalFileLR.scala

@@ -25,7 +25,8 @@ import breeze.linalg.{Vector, DenseVector}
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.classification.LogisticRegression
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 object LocalFileLR {
   val D = 10   // Numer of dimensions
@@ -41,7 +42,8 @@ object LocalFileLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use the LogisticRegression method found in org.apache.spark.mllib.classification
+        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/LocalLR.scala

@@ -25,7 +25,8 @@ import breeze.linalg.{Vector, DenseVector}
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.classification.LogisticRegression
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 object LocalLR {
   val N = 10000  // Number of data points
@@ -48,7 +49,8 @@ object LocalLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use the LogisticRegression method found in org.apache.spark.mllib.classification
+        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkHdfsLR.scala

@@ -32,7 +32,8 @@ import org.apache.spark.scheduler.InputFormatInfo
  * Logistic regression based classification.
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.classification.LogisticRegression
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 object SparkHdfsLR {
   val D = 10   // Numer of dimensions
@@ -54,7 +55,8 @@ object SparkHdfsLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use the LogisticRegression method found in org.apache.spark.mllib.classification
+        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkLR.scala

@@ -30,7 +30,8 @@ import org.apache.spark._
  * Usage: SparkLR [slices]
  *
  * This is an example implementation for learning how to use Spark. For more conventional use,
- * please refer to org.apache.spark.mllib.classification.LogisticRegression
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 object SparkLR {
   val N = 10000  // Number of data points
@@ -53,7 +54,8 @@ object SparkLR {
   def showWarning() {
     System.err.println(
       """WARN: This is a naive implementation of Logistic Regression and is given as an example!
-        |Please use the LogisticRegression method found in org.apache.spark.mllib.classification
+        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
         |for more conventional use.
       """.stripMargin)
   }

examples/src/main/scala/org/apache/spark/examples/SparkPageRank.scala

@@ -28,13 +28,28 @@ import org.apache.spark.{SparkConf, SparkContext}
  * URL         neighbor URL
  * ...
  * where URL and their neighbors are separated by space(s).
+ *
+ * This is an example implementation for learning how to use Spark. For more conventional use,
+ * please refer to org.apache.spark.graphx.lib.PageRank
  */
 object SparkPageRank {
+
+  def showWarning() {
+    System.err.println(
+      """WARN: This is a naive implementation of PageRank and is given as an example!
+        |Please use the PageRank implementation found in org.apache.spark.graphx.lib.PageRank
+        |for more conventional use.
+      """.stripMargin)
+  }
+
   def main(args: Array[String]) {
     if (args.length < 1) {
       System.err.println("Usage: SparkPageRank <file> <iter>")
       System.exit(1)
     }
+
+    showWarning()
+
     val sparkConf = new SparkConf().setAppName("PageRank")
     val iters = if (args.length > 0) args(1).toInt else 10
     val ctx = new SparkContext(sparkConf)

examples/src/main/scala/org/apache/spark/examples/SparkTachyonHdfsLR.scala

@@ -32,11 +32,24 @@ import org.apache.spark.storage.StorageLevel
 /**
  * Logistic regression based classification.
  * This example uses Tachyon to persist rdds during computation.
+ *
+ * This is an example implementation for learning how to use Spark. For more conventional use,
+ * please refer to either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+ * org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS based on your needs.
  */
 object SparkTachyonHdfsLR {
   val D = 10   // Numer of dimensions
   val rand = new Random(42)
 
+  def showWarning() {
+    System.err.println(
+      """WARN: This is a naive implementation of Logistic Regression and is given as an example!
+        |Please use either org.apache.spark.mllib.classification.LogisticRegressionWithSGD or
+        |org.apache.spark.mllib.classification.LogisticRegressionWithLBFGS
+        |for more conventional use.
+      """.stripMargin)
+  }
+
   case class DataPoint(x: Vector[Double], y: Double)
 
   def parsePoint(line: String): DataPoint = {
@@ -51,6 +64,9 @@ object SparkTachyonHdfsLR {
   }
 
   def main(args: Array[String]) {
+
+    showWarning()
+
     val inputPath = args(0)
     val sparkConf = new SparkConf().setAppName("SparkTachyonHdfsLR")
     val conf = new Configuration()