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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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/**

 * @test

 * @summary Calculates Fibonacci numbers "recursively" via threads and compares

 *     the result with the classical calculation.

 *     This test is skipped on 32-bit Windows: limited virtual space on Win-32

 *     make this test inherently unstable on Windows with 32-bit VM data model.

 * @requires !(os.family == "windows" & sun.arch.data.model == "32")

 * @modules java.base/jdk.internal.misc

 * @library /test/lib

 * @run main/othervm Fibonacci 15

 */

import jdk.test.lib.Asserts;

public class Fibonacci extends Thread {

    private int index;

    private int value;

    private Fibonacci left;

    private Fibonacci right;

    public Fibonacci(int i) {

        index = i;

    }

    private int getValue() {

        return value;

    }

    @Override

    public void run() {

        if (index == 0 || index == 1) {

            // base cases, 0 Fibonacci number = 0, 1 Fibonacci number = 1

            value = index;

        } else {

            // inductive cases

            left = new Fibonacci(index - 2);

            right = new Fibonacci(index - 1);

            left.start();

            right.start();

            try {

                left.join();

                right.join();

            } catch (InterruptedException e) {

                throw new Error("InterruptedException for index " + index, e);

            }

            // compute and terminate

            value = left.getValue() + right.getValue();

        }

    }

    public static int traditionalFibonacci(int n) {

        int n1 = 0, n2 = 1, nn = 0;

        if (n == 0 || n == 1) {

           nn = n;

        }

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

            nn = n2 + n1;

            n1 = n2;

            n2 = nn;

        }

        return nn;

    }

    public static void main(String[] args) throws Error,AssertionError {

        int expected;

        int number;

        Fibonacci recursiveFibonacci;

        if (args.length != 1) {

            throw new Error("Error: args.length must be 1");

        }

        number = Integer.parseInt(args[0]);

        recursiveFibonacci = new Fibonacci(number);

        recursiveFibonacci.start();

        try {

            recursiveFibonacci.join();

        } catch (InterruptedException e) {

            throw new Error("InterruptedException in main thread", e);

        }

        expected = traditionalFibonacci(number);

        System.out.println("Fibonacci[" + number + "] = " + expected);

        Asserts.assertEQ(recursiveFibonacci.getValue(), expected,

                          "Unexpected calculated value: " + recursiveFibonacci.getValue() + " expected " + expected );

    }

}