List <T> vs array perfomance

Question

I am trying to set List <int> value

List< int > a;
//...
a[i] = X;

ilspy shows that the setup compiles to:

callvirt instance void class [mscorlib]System.Collections.Generic.List`1<int32>::set_Item(int32, !0)

But this code

int[] b;
//...
b[i] = Y;

compiles to

stelem.i4

And it was 7 times faster with my standard.

As I understand it, a virtual call is more expensive than a stele. Is it possible to use List <T> with perfomace array

Update

the code:

   static void Main(string[] args)
    {
        int N = int.Parse(args[0]);
        int M = int.Parse(args[1]);

        var sw = new Stopwatch();
        sw.Start();
        int[] a = new int[N];
        for (int k = 0; k < M; ++k)
        {
            for (int i = 0; i < N; ++i)
            {
                a[i] = i * 2;
                a[i] -= i;
                a[i] += 1;
            }
        }
        sw.Stop();
        Console.WriteLine(sw.ElapsedMilliseconds + ":" + a[N - 1]);

        var b = new List<int>(N);
        for (int i = 0; i < N; ++i)
        {
            b.Add(0);
        }
        sw.Restart();
        for (int k = 0; k < M; ++k)
        {
            for (int i = 0; i < N; ++i)
            {
                b[i] = i * 2;
                b[i] -= i;
                b[i] += 1;
            }
        }
        sw.Stop();
        Console.WriteLine(sw.ElapsedMilliseconds + ":" + b[N - 1]);
    }

Launch and output:

> ./Console.exe 1000000 100

166:1000000
1467:1000000

Answer 1

No.

List<T>wraps an array, and it has some necessary overhead (primarily because it is a class). Also, operations, such as inserting and deleting, are expensive, especially when this causes a reordering of all the other elements in the list.

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