方法：蒙特卡罗法，又叫随机抽样或统计
步骤
1.构造一个边长为1的正方形和1/4的圆（正方形面积1大于圆面积π/4）
2.随机向正方形内随机找n个点，计算每一个点到圆心的距离，小于1的就是圆内的点，假设数量是count
3. 4*count/n的值就是π的值，spark中的pi就是用这种方法算的
代码语言：javascript
复制
val sparkSession = SparkSession.builder().master("local).getOrCreate()
val sc = sparkSession.sparkContext
val slices = 6
val n = 600000
val count = spark.parallelize(1 to n, slices).map { i =>
val x = random * 2 - 1
val y = random * 2 - 1
if ( x*x + y*y < 1) 1 else 0
}.reduce(_ + _)
val pi = 4.0 * count / n
println(pi)
sparkSession.stop()代码语言：javascript
复制
object WordCount {def main(args: Array[String]): Unit = {
val conf = new SparkConf().setAppName("wordcount")
val sc = new SparkContext(conf)
val input = sc.textFile("/data/spark/demo/word_count")
val lines = input.flatMap(line => line.split(" "))
val count = lines.map(word => (word, 1)).reduceByKey(_ + _)
val output = count.saveAsTextFile("/data/spark/demo/word_count_result")
}
}File - Project Structure - Artifacts - "+" - Jar - from modules
Build - Build Artifacts
./bin/spark-submit
--mater spark://localhost
--class WordCount /data/spark/demo/jar/spark-demo.jar
参考
