.Net ImmutableList<T> Benchmarks

benchmark_ms_ImmutableList.cs

const int SIZE = 1_000_000;
const int HALF_SIZE = 500_000;

[Benchmark]
public void ms_mutable_list()
{
    var ms_list = new List<int>();
    for (int i = 0; i < SIZE; i++) ms_list.Add(i);
}

[Benchmark]
public void ms_builder_good()
{
    var ms_list = ImmutableList<int>.Empty;
    var builder = ms_list.ToBuilder();

    for (int i = 0; i < SIZE; i++)builder.Add(i);
    
    ms_list = builder.ToImmutableList();
}

[Benchmark]
public void ms_builder_bad()
{
    var ms_list = ImmutableList<int>.Empty;
    for (int i = 0; i < SIZE; i++) 
    {
        var builder = ms_list.ToBuilder();
        builder.Add(i);
        ms_list = builder.ToImmutableList(); 
    }
}

[Benchmark]
public void ms_builder_unpack()
{
    var ms_list = ImmutableList<int>.Empty;
    var builder = ms_list.ToBuilder();

    for (int i = 0; i < HALF_SIZE; i++) builder.Add(i);

    ms_list = builder.ToImmutableList();

    builder = ms_list.ToBuilder();

    for (int i = HALF_SIZE; i < SIZE; i++) builder.Add(i);

    ms_list = builder.ToImmutableList();
}