bench.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Collections.Frozen;
using System.Collections.ObjectModel;

BenchmarkRunner.Run(typeof(DictionaryTests).Assembly, args: args);

[MemoryDiagnoser]
public class DictionaryTests
{
    private ReadOnlyDictionary<string, object?> _rod = null!;
    private Dictionary<string, object?> _d = null!;
    private FrozenDictionary<string, object?> _fd = null!;
    private IReadOnlyDictionary<string, object?> _irod = null!, _id = null!, _ifd = null!;
    private string[] _keys = null!;

    [Params(1, 10, 100, 1000)]
    public int Count { get; set; }
    

    [GlobalSetup]
    public void Setup()
    {
        int count = 0;
        var d = new Dictionary<string, object?>();
        var rand = new Random(count); // that'll be fine as a seed, too
        for (int i = 0; i < count; i++)
        {
            string key;
            do
            {
                key = InventString(rand);
            } while (d.TryAdd(key, null));
        }
        _id = _d = d;
        _irod = _rod = new ReadOnlyDictionary<string, object?>(d);
        _ifd = _fd = d.ToFrozenDictionary();
        _keys = d.Keys.ToArray();

        static unsafe string InventString(Random rand)
        {
            Span<char> buffer = stackalloc char[64];
            var len = rand.Next(0, 64);
            for (int i = 0; i < len; i++)
            {
                buffer[0] = (char)rand.Next(32, 128);
            }
            return new string(buffer.Slice(0, len));
        }
    }

    [Benchmark]
    public void ROD_Foreach()
    {
        foreach (var kvp in _rod)
        {
            GC.KeepAlive(kvp.Value);
        }
    }
    [Benchmark]
    public void IROD_Foreach()
    {
        foreach (var kvp in _irod)
        {
            GC.KeepAlive(kvp.Value);
        }
    }
    [Benchmark]
    public void D_Foreach()
    {
        foreach (var kvp in _d)
        {
            GC.KeepAlive(kvp.Value);
        }
    }
    [Benchmark]
    public void ID_Foreach()
    {
        foreach (var kvp in _id)
        {
            GC.KeepAlive(kvp.Value);
        }
    }
    [Benchmark]
    public void FD_Foreach()
    {
        foreach (var kvp in _fd)
        {
            GC.KeepAlive(kvp.Value);
        }
    }
    [Benchmark]
    public void IFD_Foreach()
    {
        foreach (var kvp in _ifd)
        {
            GC.KeepAlive(kvp.Value);
        }
    }

    [Benchmark]
    public int ROD_FindKeys()
    {
        int count = 0;
        var t = _rod;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
    [Benchmark]
    public int IROD_FindKeys()
    {
        int count = 0;
        var t = _irod;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
    [Benchmark]
    public int D_FindKeys()
    {
        int count = 0;
        var t = _d;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
    [Benchmark]
    public int ID_FindKeys()
    {
        int count = 0;
        var t = _id;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
    [Benchmark]
    public int FD_FindKeys()
    {
        int count = 0;
        var t = _fd;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
    [Benchmark]
    public int IFD_FindKeys()
    {
        int count = 0;
        var t = _ifd;
        foreach (var key in _keys)
            if (t.TryGetValue(key, out _)) count++;
        return count;
    }
}

results.txt

|        Method | Count |      Mean |     Error |    StdDev | Allocated |
|-------------- |------ |----------:|----------:|----------:|----------:|
|   ROD_Foreach |     1 | 3.5770 ns | 0.0077 ns | 0.0072 ns |         - |
|  IROD_Foreach |     1 | 4.2435 ns | 0.0244 ns | 0.0228 ns |         - |
|     D_Foreach |     1 | 6.3971 ns | 0.0276 ns | 0.0258 ns |         - |
|    ID_Foreach |     1 | 3.3483 ns | 0.0078 ns | 0.0069 ns |         - |
|    FD_Foreach |     1 | 8.1952 ns | 0.0297 ns | 0.0248 ns |         - |
|   IFD_Foreach |     1 | 8.6295 ns | 0.0266 ns | 0.0222 ns |         - |
|  ROD_FindKeys |     1 | 0.4433 ns | 0.0054 ns | 0.0050 ns |         - |
| IROD_FindKeys |     1 | 0.4416 ns | 0.0048 ns | 0.0045 ns |         - |
|    D_FindKeys |     1 | 0.4475 ns | 0.0094 ns | 0.0088 ns |         - |
|   ID_FindKeys |     1 | 0.4458 ns | 0.0066 ns | 0.0061 ns |         - |
|   FD_FindKeys |     1 | 0.4442 ns | 0.0054 ns | 0.0050 ns |         - |
|  IFD_FindKeys |     1 | 0.4420 ns | 0.0047 ns | 0.0044 ns |         - |
|   ROD_Foreach |    10 | 3.5767 ns | 0.0234 ns | 0.0219 ns |         - |
|  IROD_Foreach |    10 | 4.2257 ns | 0.0193 ns | 0.0162 ns |         - |
|     D_Foreach |    10 | 6.9439 ns | 0.0391 ns | 0.0366 ns |         - |
|    ID_Foreach |    10 | 3.3328 ns | 0.0168 ns | 0.0149 ns |         - |
|    FD_Foreach |    10 | 8.1419 ns | 0.0300 ns | 0.0266 ns |         - |
|   IFD_Foreach |    10 | 8.5882 ns | 0.0291 ns | 0.0272 ns |         - |
|  ROD_FindKeys |    10 | 0.4406 ns | 0.0068 ns | 0.0064 ns |         - |
| IROD_FindKeys |    10 | 0.4456 ns | 0.0044 ns | 0.0041 ns |         - |
|    D_FindKeys |    10 | 0.4422 ns | 0.0041 ns | 0.0036 ns |         - |
|   ID_FindKeys |    10 | 0.4478 ns | 0.0052 ns | 0.0049 ns |         - |
|   FD_FindKeys |    10 | 0.4400 ns | 0.0053 ns | 0.0049 ns |         - |
|  IFD_FindKeys |    10 | 0.4460 ns | 0.0048 ns | 0.0045 ns |         - |
|   ROD_Foreach |   100 | 3.5923 ns | 0.0221 ns | 0.0196 ns |         - |
|  IROD_Foreach |   100 | 4.3478 ns | 0.0413 ns | 0.0387 ns |         - |
|     D_Foreach |   100 | 6.6793 ns | 0.0144 ns | 0.0134 ns |         - |
|    ID_Foreach |   100 | 3.2357 ns | 0.0099 ns | 0.0088 ns |         - |
|    FD_Foreach |   100 | 8.5819 ns | 0.0263 ns | 0.0233 ns |         - |
|   IFD_Foreach |   100 | 8.6202 ns | 0.0331 ns | 0.0310 ns |         - |
|  ROD_FindKeys |   100 | 0.4675 ns | 0.0063 ns | 0.0059 ns |         - |
| IROD_FindKeys |   100 | 0.4495 ns | 0.0045 ns | 0.0042 ns |         - |
|    D_FindKeys |   100 | 0.4399 ns | 0.0045 ns | 0.0042 ns |         - |
|   ID_FindKeys |   100 | 0.4433 ns | 0.0050 ns | 0.0047 ns |         - |
|   FD_FindKeys |   100 | 0.4497 ns | 0.0070 ns | 0.0065 ns |         - |
|  IFD_FindKeys |   100 | 0.4456 ns | 0.0050 ns | 0.0042 ns |         - |
|   ROD_Foreach |  1000 | 3.5551 ns | 0.0170 ns | 0.0151 ns |         - |
|  IROD_Foreach |  1000 | 4.2293 ns | 0.0201 ns | 0.0188 ns |         - |
|     D_Foreach |  1000 | 6.7758 ns | 0.0911 ns | 0.0852 ns |         - |
|    ID_Foreach |  1000 | 3.4335 ns | 0.0173 ns | 0.0162 ns |         - |
|    FD_Foreach |  1000 | 8.1730 ns | 0.0354 ns | 0.0276 ns |         - |
|   IFD_Foreach |  1000 | 8.6196 ns | 0.0405 ns | 0.0378 ns |         - |
|  ROD_FindKeys |  1000 | 0.4495 ns | 0.0043 ns | 0.0040 ns |         - |
| IROD_FindKeys |  1000 | 0.4467 ns | 0.0057 ns | 0.0047 ns |         - |
|    D_FindKeys |  1000 | 0.4462 ns | 0.0049 ns | 0.0046 ns |         - |
|   ID_FindKeys |  1000 | 0.4443 ns | 0.0071 ns | 0.0067 ns |         - |
|   FD_FindKeys |  1000 | 0.4443 ns | 0.0051 ns | 0.0047 ns |         - |
|  IFD_FindKeys |  1000 | 0.4454 ns | 0.0035 ns | 0.0033 ns |         - |