Find element in array

find_element.cs

using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Jobs;
using BenchmarkDotNet.Running;

#pragma warning disable CS8618

var summary = BenchmarkRunner.Run<MainTest>();

[SimpleJob(RuntimeMoniker.Net70, baseline: true)]
[WarmupCount(2)]
[IterationCount(2)]
[MemoryDiagnoser]
public class MainTest
{
    const int N          = 1_000_000;
    const int ITERATIONS = 10000;

    int[] src;

    [IterationSetup]
    public void Setup()
    {
        src = Enumerable.Range(0, N).Concat(Enumerable.Range(0, N)).Append(-1).ToArray();
    }

    [Benchmark]
    public int TestForEach()
    {
        var r = 0;
        for (var iteration = 0; iteration < ITERATIONS; iteration++)
        {
            r = 0;
            foreach (var s in src)
                r ^= s;
        }

        return r;
    }

    [Benchmark]
    public unsafe int TestVector128()
    {
        var r = 0;
        for (var iteration = 0; iteration < ITERATIONS; iteration++)
        {
            fixed (int* srcPtr = src)
            {
                var pointer = srcPtr;
                var acc     = Vector128<int>.Zero;
                for (var i = 0; i < src.Length / 4; i++, pointer += 4)
                    acc = Sse2.Xor(acc, Vector128.Load(pointer));

                r = 0;
                for (var i = 0; i < 4; i++)
                    r ^= acc.GetElement(i);
            }

            for (var i = src.Length / 4 * 4; i < src.Length; i++)
                r ^= src[i];
        }

        return r;
    }

    [Benchmark]
    public unsafe int TestVector256()
    {
        var r = 0;
        for (var iteration = 0; iteration < ITERATIONS; iteration++)
        {
            fixed (int* srcPtr = src)
            {
                var pointer = srcPtr;
                var acc     = Vector256<int>.Zero;
                for (var i = 0; i < src.Length / 8; i++, pointer += 8)
                    acc = Avx2.Xor(acc, Vector256.Load(pointer));

                r = 0;
                for (var i = 0; i < 8; i++)
                    r ^= acc.GetElement(i);

                for (var i = src.Length / 8 * 8; i < src.Length; i++)
                    r ^= src[i];
            }
        }

        return r;
    }
}