/**
 * A Simple class to illustrate the problems with timing tasks, even on
 * computers with known loading
 * 
 * @author gtowell Created: Sep 2020 Modified: Mar 1, 2021 gtowell Modified: Sep
 *         8, 2021 gtowell
 */
public class Timer {
    private static final int REPS = 2; // number of trials
    private static final int NANOS_SEC = 1000000000; // nanosec per sec

    /**
     * A very silly function that does a lot of work based on the size of the input
     * array. However, it never actually looks at the contents of that array
     * 
     * @param data the input array (content ignored)
     * @return a largely meaningless value
     */
    public double doSomething(int[] data) {
        double k = 0;
        for (long i = 0; i < data.length; i++) {
            for (long j = 0; j < data.length; j++) {
                k += Math.sqrt(i * j);
            }
        }
        return k;
    }

    /**
     * The main, Does a timing test doubling the size of the input for every step
     * 
     * @param args
     */
    public static void main(String[] args) {
        Timer timer = new Timer();
        long data[] = new long[REPS];
        for (int j = 1000; j < 65001; j = j * 2) {
            for (int i = 0; i < REPS; i++) {
                long start = System.nanoTime();
                timer.doSomething(new int[j]);
                long finish = System.nanoTime();
                data[i] = (finish - start);
                System.out.println(String.format("%d %.4f", j, (double) (finish - start) / NANOS_SEC));
            }
        }
    }
}