SPARK-3716 [GraphX] Update Analytics.scala for partitionStrategy assignment

Previously, when the val partitionStrategy was created it called a function in the Analytics object which was a copy of the PartitionStrategy.fromString() method. This function has been removed, and the assignment of partitionStrategy now uses the PartitionStrategy.fromString method instead. In this way, it better matches the declarations of edge/vertex StorageLevel variables.

Author: NamelessAnalyst <NamelessAnalyst@users.noreply.github.com>

Closes #2569 from NamelessAnalyst/branch-1.1 and squashes the following commits:

c24ff51 [NamelessAnalyst] Update Analytics.scala

graphx/src/main/scala/org/apache/spark/graphx/lib/Analytics.scala

@@ -45,17 +45,6 @@ object Analytics extends Logging {
     }
     val options = mutable.Map(optionsList: _*)
 
-    def pickPartitioner(v: String): PartitionStrategy = {
-      // TODO: Use reflection rather than listing all the partitioning strategies here.
-      v match {
-        case "RandomVertexCut" => RandomVertexCut
-        case "EdgePartition1D" => EdgePartition1D
-        case "EdgePartition2D" => EdgePartition2D
-        case "CanonicalRandomVertexCut" => CanonicalRandomVertexCut
-        case _ => throw new IllegalArgumentException("Invalid PartitionStrategy: " + v)
-      }
-    }
-
     val conf = new SparkConf()
       .set("spark.serializer", "org.apache.spark.serializer.KryoSerializer")
       .set("spark.kryo.registrator", "org.apache.spark.graphx.GraphKryoRegistrator")
@@ -66,7 +55,7 @@ object Analytics extends Logging {
       sys.exit(1)
     }
     val partitionStrategy: Option[PartitionStrategy] = options.remove("partStrategy")
-      .map(pickPartitioner(_))
+      .map(PartitionStrategy.fromString(_))
     val edgeStorageLevel = options.remove("edgeStorageLevel")
       .map(StorageLevel.fromString(_)).getOrElse(StorageLevel.MEMORY_ONLY)
     val vertexStorageLevel = options.remove("vertexStorageLevel")
@@ -106,7 +95,7 @@ object Analytics extends Logging {
 
         if (!outFname.isEmpty) {
           logWarning("Saving pageranks of pages to " + outFname)
-          pr.map{case (id, r) => id + "\t" + r}.saveAsTextFile(outFname)
+          pr.map { case (id, r) => id + "\t" + r }.saveAsTextFile(outFname)
         }
 
         sc.stop()
@@ -128,7 +117,7 @@ object Analytics extends Logging {
         val graph = partitionStrategy.foldLeft(unpartitionedGraph)(_.partitionBy(_))
 
         val cc = ConnectedComponents.run(graph)
-        println("Components: " + cc.vertices.map{ case (vid,data) => data}.distinct())
+        println("Components: " + cc.vertices.map { case (vid, data) => data }.distinct())
         sc.stop()
 
       case "triangles" =>
@@ -146,7 +135,7 @@ object Analytics extends Logging {
           minEdgePartitions = numEPart,
           edgeStorageLevel = edgeStorageLevel,
           vertexStorageLevel = vertexStorageLevel)
-        // TriangleCount requires the graph to be partitioned
+          // TriangleCount requires the graph to be partitioned
           .partitionBy(partitionStrategy.getOrElse(RandomVertexCut)).cache()
         val triangles = TriangleCount.run(graph)
         println("Triangles: " + triangles.vertices.map {