import java.util.concurrent.ExecutionException;

import java.util.concurrent.ForkJoinPool;

import java.util.concurrent.Future;

import java.util.concurrent.RecursiveTask;

import java.util.stream.IntStream;

/**

* @author wincher

* @date 2018/8/13

* <p> PACKAGE_NAME <p>

*/

public class CountTask extends RecursiveTask<Integer> {

private static final int THRESHOLD = 100;

private final int start;

private final int end;

public CountTask(int start, int end) {

this.start = start;

this.end = end;

}

int sum = 0;

@Override

protected Integer compute() {

// if task size is small enough

boolean canCompute = (end - start) <= THRESHOLD;

if (canCompute) {

for (int i = start; i <= end; i++) {

sum += i;

}

return sum;

}

// split

int middle = (end + start) / 2;

System.out.println("Middle: " + middle);

CountTask leftTask = new CountTask(start, middle);

leftTask.fork();

CountTask rightTask = new CountTask(1 + middle, end);

int rightValue = rightTask.compute();

int leftValue = leftTask.join();

sum = leftValue + rightValue;

return sum;

}

public static void main(String[] args) {

// ForkJoinPool forkJoinPool = new ForkJoinPool();

// CountTask task = new CountTask(1, 100);

// Future result = forkJoinPool.submit(task);

// try {

// long startTime = System.nanoTime();

// System.out.println(result.get() + " : " + (System.nanoTime() - startTime));

// } catch (InterruptedException e) {

// e.printStackTrace();

// } catch (ExecutionException e) {

// e.printStackTrace();

// }

long start = System.nanoTime();

long sum = 0;

// for (long i = 0; i < 100_000_000; i++) {

// sum += i;

// }

// System.out.println(sum + "time:" + ((System.nanoTime() - start) / 1_000_000));

// long fastest = Long.MAX_VALUE;

// long end;

// System.out.println("********");

// for (int i = 1; i <= 10; i++) {

// start = System.nanoTime();

// for (long ii = 0; ii < 100_000_000; ii++) {

// sum += ii;

// }

// end = (System.nanoTime() - start) / 1_000_000;

// fastest = (end < fastest) ? end : fastest;

// }

// System.out.println(sum + "time:" + fastest);

long fastest = Long.MAX_VALUE;

long end;

System.out.println("********");

for (int i = 1; i <= 10; i++) {

start = System.nanoTime();

IntStream.rangeClosed(1, 1_000_000_000).parallel().sum();

end = (System.nanoTime() - start) / 1_000_000;

fastest = (end < fastest) ? end : fastest;

}

System.out.println(sum + "time:" + fastest);

}

}