Interface vs direct calls

BenchInterfaceVsIndirectCalls.cs

// Gist that shows the difference of an interface call
// Two cases in this benchmark:
// - Dictionary that should not inline
// - List that should inline
// We are also using the enumerator to show the impact on allocation as well.

/*
             Method |      Mean |     Error |    StdDev | Gen 0/1k Op | Gen 1/1k Op | Gen 2/1k Op | Allocated Memory/Op |
------------------- |----------:|----------:|----------:|------------:|------------:|------------:|--------------------:|
  ProcessDictionary | 27.109 ns | 0.1258 ns | 0.1176 ns |           - |           - |           - |                   - |
 ProcessIDictionary | 51.636 ns | 0.3541 ns | 0.3312 ns |      0.0114 |           - |           - |                48 B |
        ProcessList |  1.237 ns | 0.0298 ns | 0.0265 ns |           - |           - |           - |                   - |
       ProcessIList | 24.101 ns | 0.1926 ns | 0.1802 ns |      0.0095 |           - |           - |                40 B |
*/
using System;
using System.Collections.Generic;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

namespace BenchDictionary
{
    [MemoryDiagnoser]
    public class Program
    {
        private static Dictionary<int, int> _values;
        private static List<int> _listValues;

        static Program()
        {
            _values= new Dictionary<int, int>();
            for (int i = 0; i < 10; i++)
            {
                _values.Add(i, i);
            }
            _listValues = new List<int>();
            _listValues.Add(0);
            _listValues.Add(1);
            _listValues.Add(2);
            
        }

        [Benchmark]
        public static int ProcessDictionary()
        {
            return _values[0] + _values[1] + _values[2] + _values.GetEnumerator().Current.Key;        }
        
        [Benchmark]
        public static int ProcessIDictionary()
        {
            return ((IDictionary<int, int>) _values)[0] + ((IDictionary<int, int>) _values)[1] + ((IDictionary<int, int>) _values)[2] + ((IDictionary<int, int>) _values).GetEnumerator().Current.Key;
        }
        
        [Benchmark]
        public static int ProcessList()
        {
            return _listValues[0] + _listValues[1] + _listValues[2] + _listValues.GetEnumerator().Current;
        }
        
        [Benchmark]
        public static int ProcessIList()
        {
            return ((IList<int>) _listValues)[0] + ((IList<int>) _listValues)[1] + ((IList<int>) _listValues)[2] + ((IList<int>) _listValues).GetEnumerator().Current;
        }

        static void Main(string[] args)
        {
            BenchmarkRunner.Run<Program>();
        }
    }
}