SIMD Benchmark: Span vs Array

SumBench.cs

using BenchmarkDotNet.Attributes;
using System;
using System.Linq;
using System.Numerics;
using System.Runtime.InteropServices;

namespace SIMDBench
{
    public class SumBench
    {
        public static float Sum(Span<float> a)
        {
            var av = MemoryMarshal.Cast<float, Vector<float>>(a);
            var vSum = Vector<float>.Zero;

            foreach (var v in av)
                vSum += v;

            var sum = Vector.Dot(vSum, Vector<float>.One);

            a = a.Slice(av.Length * Vector<float>.Count);

            foreach (var f in a)
                sum += f;

            return sum;
        }

        // From https://github.com/giladfrid009/SimpleSIMD/blob/master/SimpleSIMD/Reduction/Sum.cs
        public static float Sum(float[] array)
        {
            Vector<float> vSum = Vector<float>.Zero;
            float sum;
            int vLen = Vector<float>.Count;
            int i;

            for (i = 0; i <= array.Length - vLen; i += vLen)
            {
                vSum += new Vector<float>(array, i);
            }

            sum = Vector.Dot(vSum, Vector<float>.One);

            for (; i < array.Length; i++)
            {
                sum += array[i];
            }

            return sum;
        }

        public float[] Data;

        [Params(10, 16, 100, 128, 1000, 1024, 60000, 65536)]
        public int N;

        [GlobalSetup]
        public void GlobalSetup()
        {
            Data = Enumerable.Range(0, N).Select(i => (float)i).ToArray();
        }

        [Benchmark]
        public float Span() => Sum(Data.AsSpan());

        [Benchmark(Baseline = true)]
        public float Array() => Sum(Data);
    }
}