diff --git a/examples/src/main/scala/spark/examples/SparkPageRank.scala b/examples/src/main/scala/spark/examples/SparkPageRank.scala new file mode 100644 index 0000000000000000000000000000000000000000..4e41c026a41bb4ccdccee6156fd656811bcf4784 --- /dev/null +++ b/examples/src/main/scala/spark/examples/SparkPageRank.scala @@ -0,0 +1,50 @@ +package spark.examples + +import spark.SparkContext._ +import spark.SparkContext + + +/** + * Computes the PageRank of URLs from an input file. Input file should + * be in format of: + * URL neighbor URL + * URL neighbor URL + * URL neighbor URL + * ... + * where URL and their neighbors are separated by space(s). + */ +object SparkPageRank { + def main(args: Array[String]) { + if (args.length < 3) { + System.err.println("Usage: PageRank <master> <file> <number_of_iterations>") + System.exit(1) + } + var iters = args(2).toInt + val ctx = new SparkContext(args(0), "PageRank", System.getenv("SPARK_HOME"), Seq(System.getenv("SPARK_EXAMPLES_JAR"))) + val lines = ctx.textFile(args(1), 1) + val links = lines.map{s => + val parts = s.split("\\s+") + (parts(0), parts(1)) + }.distinct().groupByKey().cache() + var ranks = links.mapValues(v => 1.0) + + for (i <- 1 to iters) { + val contribs = links.join(ranks).values.flatMap{ case (urls, rank) => + val size = urls.size + urls.map(url => (url, rank / size)) + } + + ranks = contribs.groupByKey().mapValues{ranks => + val sumRanks = ranks.foldLeft(0.0)(_ + _) + 0.15 + sumRanks * 0.85 + } + } + + val output = ranks.collect() + output.foreach(tup => println(tup._1 + " has rank: " + tup._2 + ".")) + + ctx.stop() + System.exit(0) + } +} +