ArrayEnumerationBenchmark.cs

using System;
using System.Buffers;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;

namespace Benchs.Arrays;

[SimpleJob(RuntimeMoniker.Net60)]
[SimpleJob(RuntimeMoniker.NetCoreApp31)]
[SimpleJob(RuntimeMoniker.Net461)]
[MeanColumn]
public class ArrayRandomReadBenchmark
{
    [Benchmark(Baseline = true)]
    public int ArrayIndex()
    {
        var sum = 0;
        foreach (var index in _indices)
        {
            sum += _array[index];
        }

        return sum;
    }

    [Benchmark]
    public int BlackMagic()
    {
        var sum = 0;
        ref var data = ref GetArrayDataReference(_array);
        foreach (var index in _indices)
        {
            sum += Unsafe.Add(ref data, index);
        }

        return sum;
    }

    [Benchmark]
    public int MemoryIndex()
    {
        var sum = 0;
        foreach (var index in _indices)
        {
            sum += _memory.Span[index];
        }

        return sum;
    }

    [Benchmark]
    public unsafe int UnsafeFixed()
    {
        var sum = 0;
        foreach (var index in _indices)
        {
            fixed (int* arrayPtr = &_array[0])
            {
                sum += *(arrayPtr + index);
            }
        }

        return sum;
    }

    [Benchmark]
    public unsafe int UnsafePined()
    {
        var sum = 0;
        foreach (var index in _indices)
        {
            sum += *((int*)_memoryHandle.Pointer + index);
        }

        return sum;
    }

    #region Configuration

    private int[] _array = null!;
    private ReadOnlyMemory<int> _memory;
    private ReadOnlyMemory<int> _pinedMemory;
    private MemoryHandle _memoryHandle;
    private int[] _indices = null!;

    [GlobalSetup]
    public void Init()
    {
        const int count = 1021;

        _array = new int[count];
        _memory = new ReadOnlyMemory<int>(_array);
        _pinedMemory = new ReadOnlyMemory<int>(_array);
        _memoryHandle = _pinedMemory.Pin();

        var rnd = new Random(1234);
        for (var i = 0; i < count; i++)
        {
            _array[i] = rnd.Next(0, 10);
        }

        _indices = new int[count];
        for (var i = 0; i < count; i++)
        {
            _indices[i] = rnd.Next(0, _array.Length - 1);
        }
    }

    [GlobalCleanup]
    public void Clear()
    {
        _memoryHandle.Dispose();
    }

    #endregion

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static ref T GetArrayDataReference<T>(T[] array) =>
        ref Unsafe.As<byte, T>(ref Unsafe.As<RawArrayData>(array).Data);

    [StructLayout(LayoutKind.Sequential)]
    private sealed class RawArrayData
    {
        public IntPtr Length;
        public byte Data;
    }
}