Spark-Persist

import org.apache.spark.{SparkConf, SparkContext}

/**
  * Created by MC on 2018/6/11.
  * 本文介绍将程序加载到内存
  *
  */
object PersisTest {
  def WordCount(sc : SparkContext): String ={
    val start = System.currentTimeMillis()
    val file = sc.textFile("D://B/c.txt")
//    val rdd1 = file.flatMap(_.split(" ")).map((_,1)).reduceByKey(_ + _).sortByKey().persist().collect()
    val flatMap = file.flatMap(_.split("\\s"))
    val map = flatMap.map((_,1))
  //.persist是将程序久化的内存
    val rsp = map.reduceByKey(_ + _).sortByKey().persist()
    val key = rsp.foreach(println(_))
    val end = System.currentTimeMillis()
    println("--------------"+(end-start)+"--------------")
    key.toString()
    val end1 = System.currentTimeMillis()
    println("--------------"+(end1-end)+"--------------")
    key.toString()
    val end2 = System.currentTimeMillis()
    println("--------------"+(end2-end1)+"--------------")
    key.toString()
  }
  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setMaster("local").setAppName("GroupTopN")
    val sc = new SparkContext(conf)
    var result: String = ""
      result=WordCount(sc)
    println(result)
    sc.stop
  }
}
    //运行结果
//第一次运行计算
//    --------------464--------------
//运行计算并加载到内存
//    --------------757--------------
//直接读取内存
//      --------------15--------------

//运行结果

(Job,1)
(My,3)
(Second,,1)
(So,1)
(Thank,1)
(Third,1)
(a,4)
(an,1)
(and,5)
(architect,1)
(be,2)
(become,1)
(believe,1)
(big,1)
(can,4)
(crazy.,1)
(data,1)
(data,,1)
(dream,1)
(excellent,1)
(family,,1)
(find,1)
(first,1)
(for,1)
(from,1)
(future.,1)
(great,1)