Spark下的PageRank实现

val sc = new SparkContext(...)
val links = sc.parallelize(Array(("A",Array("D")),("B",Array("A")),("C",Array("A","B")),("D",Array("A","C"))),2).map(x => (x._1,x._2)).cache()

var ranks = sc.parallelize(Array(("A",1.0),("B",1.0),("C",1.0),("D",1.0)),2)

val iterations_num = 50

for(i <- 1 to iterations_num){
	val contribs = links.join(ranks,2).flatMap{
		case(url,(links,rank)) => links.map(dest => (dest,rank/links,size))
	}

	ranks = contribs.reduceByKey(_ + _,2).mapValues(0.15 + 0.85 * _)
}

ranks.saveAsTextFile(...)val sc = new SparkContext(...)
val links = sc.para