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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.examples;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.sql.SparkSession;
import java.util.ArrayList;
import java.util.List;
/**
* Computes an approximation to pi
* Usage: JavaSparkPi [slices]
*/
public final class JavaSparkPi {
public static void main(String[] args) throws Exception {
SparkSession spark = SparkSession
.builder()
.appName("JavaSparkPi")
.getOrCreate();
JavaSparkContext jsc = new JavaSparkContext(spark.sparkContext());
int slices = (args.length == 1) ? Integer.parseInt(args[0]) : 2;
int n = 100000 * slices;
List<Integer> l = new ArrayList<>(n);
for (int i = 0; i < n; i++) {
l.add(i);
}
JavaRDD<Integer> dataSet = jsc.parallelize(l, slices);
int count = dataSet.map(new Function<Integer, Integer>() {
@Override
public Integer call(Integer integer) {
double x = Math.random() * 2 - 1;
double y = Math.random() * 2 - 1;
return (x * x + y * y <= 1) ? 1 : 0;
}
}).reduce(new Function2<Integer, Integer, Integer>() {
@Override
public Integer call(Integer integer, Integer integer2) {
return integer + integer2;
}
});
System.out.println("Pi is roughly " + 4.0 * count / n);
spark.stop();
}
}
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