How to calculate the average of multiple Stopwatch times?

Question

So basically what i'm trying to do is calculate the average of all the Stop Watch times that my for loop produces and out put it to the Console. i know how to take an average but i dont know how to apply it to Stopwatch times. Please help?

for (int index = 0; index < iterations; index++)
        {
            // loop to generate an array of random numbers      
            for (int count = 0; count < arrayOfInts.Length; count++)
            {
                arrayOfInts[count] = r.Next(numitems);
            }
            // a random array has been created start the clock and sort it
            Stopwatch elpased = new Stopwatch();
            elpased.Start();
            selectionSort(arrayOfInts);
            elpased.Stop();

            if (iterations == iterations) 
            {

                var average = elpased.Elapsed;

                Console.WriteLine ("Time for ___ sort to complete: " + elpased.Elapsed.ToString ());
            }
            }



            Console.ReadLine();
    }

This is what i have so far.

Possible duplicate of [Find average of collection of timespans](http://stackoverflow.com/questions/8847679/find-average-of-collection-of-timespans) — Random Davis, Oct 21 '16 at 16:50
You said you know how to take the average but you're not actually taking the average. — Brandon, Oct 21 '16 at 16:51
@zzzzBov If it was a type that overrode the `==` operator and returned false based on whatever custom logic you felt like, i.e. `return false;` . — Servy, Oct 21 '16 at 17:00

score 4 · Answer 1 · edited Jul 18 '22 at 13:39

I'd suggest to use ElapsedTicks instead. And you need to store the ticks for each iteration and calculate the average afterwards:

List<long> ticks = new List<long>();
for (int index = 0; index < iterations; index++)
{
    // loop to generate an array of random numbers      
    for (int count = 0; count < arrayOfInts.Length; count++)
    {
        arrayOfInts[count] = r.Next(numitems);
    }
    
    // a random array has been created start the clock and sort it
    Stopwatch elapsed = new Stopwatch();
    elapsed.Start(); 
    selectionSort(arrayOfInts);
    elpased.Stop();
    ticks.Add(elapsed.Elapsed.Ticks);
}

double avg = ticks.Average(); // create average of ticks
TimeSpan averageTimeSpan = new TimeSpan((long)avg); // cast needed from double to long

There is a little more elegant way to produce your random number array:

arrayOfInts = Enumerable.Range(0, count).Select(i => r.Next(numitems)).ToArray();

And because LINQ uses deferred execution you could even pre-declare this "query" and call ToArray() in the iteration:

List<long> ticks = new List<long>();
IEnumerable<int> randomQuery = Enumerable.Range(0, count).Select(i => r.Next(numitems));

for (int index = 0; index < iterations; index++)
{
     //creates NEW random numbers each time, because of deferred execution
     arrayOfInts = randomQuery.ToArray(); 

     ...

Another suggestion is to let the Stopwatch measure the whole time and divide the result by iterations. Stopwatches can be resumed:

IEnumerable<int> randomQuery = Enumerable.Range(0, count).Select(i => r.Next(numitems));
Stopwatch elapsed = new Stopwatch(); // only ONE instance needed
for (int index = 0; index < iterations; index++)
{
     arrayOfInts = randomQuery.ToArray();
     elapsed.Start(); // resumes without a reset
     selectionSort(arrayOfInts);
     elpased.Stop();
}
TimeSpan averageTimeSpan = new TimeSpan(elapsed.ElapsedTicks/iterations);

Thank you very much, i made modifications to it to fix my needs. — Nnacheta Nnyagu, Oct 21 '16 at 17:35
I was trying to do something similar but was getting numbers reported that just didn't make sense. Turns out `Elapsed.Ticks` should be used instead of `ElapsedTicks` for reasons described [here](http://geekswithblogs.net/BlackRabbitCoder/archive/2012/01/12/c.net-little-pitfalls-stopwatch-ticks-are-not-timespan-ticks.aspx). — Ocelot20, Dec 22 '17 at 17:00

How to calculate the average of multiple Stopwatch times?

1 Answers1