Performance comparison of Generic and non Generic List after JIT compilation

Performance of generic and non-generic list is well known. But there is a catch. We should always consider results which comes after JIT compilation. The difference between the test run of the code snippet and running the code after JIT does its job may surprise you.

1. Now what happens when you run the test application for performance comparison.
2. When you run the application, JIT runs i.e. Just in Time compiler.
3. JIT compiles the application, optimize the code and finds the best approach to executes the code.
4. All these JIT steps are time consuming which are included in first execution, so the execution time is always way more than actual run time
5. So how you can calculate the actual run time? Simple, to check the performance of your test application with test data, call code snippet in a loop.

Example

private static void GenericListPerformance()

{

     var genList = new List<int>() { 10, 100, 13, 19, 14, 100, 99 };

     var nonGenList = new ArrayList() { 10, 100, 13, 19, 14, 100, 99 };

     var stWatch = Stopwatch.StartNew();

     genList.Sort();

     stWatch.Stop();

     Console.WriteLine("Generic List sorting "+ stWatch.Elapsed.TotalMilliseconds.ToString());

     stWatch = Stopwatch.StartNew();

     nonGenList.Sort();

     stWatch.Stop();

Console.WriteLine("Non Generic List sorting "+ stWatch.Elapsed.TotalMilliseconds.ToString());

}

Here I have created a simple method to compare the two list ArrayList and List<T>. I have used Stopwatch which is present in System.Diagnostics namespace of .net framework and then printed the messages with time.

static void Main(string[] args)

{

         for (int i = 0; i < 5; i++)

            {

                Console.WriteLine(string.Format("<--------Call Number {0} -------->",i));

                GenericListPerformance();

                Console.WriteLine();

            }

}

Now this is where I have used the actual concept. I have called the same method in main inside a loop which runs 5 times. So, when it run for first time JIT can optimize the code and find the best approach to run this code. Later, JIT will use the native code and give us the best results.

Result

See the results.

For first run the execution time is-

For Generic - 0.0263
For Non-Generic – 0.233

And later it came to be line

Generic – 0.0012, 0.0013, 0.0011, 0.0013
Non-Generic – 0.0032, 0.0026, 0.0026, 0.0029

Therefor, we should always consider the JIT time

Subscribe to my blog if you want to get notified about more detailed analysis of topics. Comment if you have any question or want me to do some analysis on the topic you want.

Thanks