Question

Even though it is good to check performance of code in terms of algorithmic analysis and Big-Oh! notation i wanted to see how much it takes for the code to execute in my PC. I had initialized a List to 9999count and removed even elements out from the them. Sadly the timespan to execute this seems to be 0:0:0. Surprised by the result there must be something wrong in the way i time the execution. Could someone help me time the code correct?

        IList<int> source = new List<int>(100);
        for (int i = 0; i < 9999; i++)
        {
            source.Add(i);
        }

        TimeSpan startTime, duration;
        startTime = Process.GetCurrentProcess().Threads[0].UserProcessorTime;

        RemoveEven(ref source);
        duration = Process.GetCurrentProcess().Threads[0].UserProcessorTime.Subtract(startTime);

        Console.WriteLine(duration.Milliseconds);
        Console.Read();

Answer 1

The most appropriate thing to use there would be Stopwatch – anything involving TimeSpan has nowhere near enough precision for this:

var watch = Stopwatch.StartNew();
// something to time
watch.Stop();
Console.WriteLine(watch.ElapsedMilliseconds);

However, a modern CPU is very fast, and it would not surprise me if it can remove them in that time. Normally, for timing, you need to repeat an operation a large number of times to get a reasonable measurement.

Aside: the ref in RemoveEven(ref source) is almost certainly not needed.