package futures;

import java.util.concurrent.*;

public class FibExec {
    final static ExecutorService exec =
            Executors.newFixedThreadPool(400);

    static int fcall(int n) throws Exception {
        if (n < 2)
            return n;
        Future<Integer> f1 = exec.submit(() -> fcall(n - 1));
        int n2 = fcall(n - 2);
        return f1.get() + n2;
    }

    public static void main(String[] args) throws Exception {
        for (int n = 0; n <= 45; n++) {
            final int fibn = n;
            Future<Integer> fib = exec.submit(() -> fcall(fibn));
            long t1 = System.currentTimeMillis();
            int f = fib.get();
            long t2 = System.currentTimeMillis();
            double tm = 1e-3*(t2-t1);
            System.out.printf("fib(%d)=%d, time=%f%n", n, f, tm);
        }
        exec.shutdown();
    }
}