Question

I’m writing a method to compute the running time for an algorithm. The algorithm is run a specified number of trials and then I compute the running time using System.currentTimeMillis(). However whenever I call the method the value always ends up being zero. Any direction towards fixing this problem is appreciated.

public long runTime(algorithm alg, int[] array, int trials)
{

    long initialTime = System.currentTimeMillis();

    for(int i = 0; i < trials; i++)
    {
        alg.runAlgorithm(array); 
    }

    return ((System.currentTimeMillis() - initialTime) / (long) trials);
}

Answer 1

((System.currentTimeMillis() - initialTime) / (long) trials);

It seems the Algorithm is taking less than a 1 ms to complete its loop, and so you need to break it even to smaller unit… Using nanoTime() may do the work for u…

Eg:

public long runTime(algorithm alg, int[] array, int trials)
{

    long initialTime = System.nanoTime();

    for(int i = 0; i < trials; i++)
    {
        alg.runAlgorithm(array); 
    }

    return ((System.nanoTime() - initialTime) / (long) trials);
}