ToolkitHighPerformanceBM.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using Microsoft.Toolkit.HighPerformance.Helpers;
using System;
using System.Threading.Tasks;

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

    [MemoryDiagnoser]
    public class BM {

        private double[] _array;

        [Params(10_000, 100_000, 1_000_000)]
        public int Size;

        [GlobalSetup]
        public void Setup() => _array = new double[Size];

        [Benchmark]
        public void SingleThreaded() {
            for (int i = 0; i < _array.Length; i++) _array[i] += 2;
        }

        [Benchmark]
        public void Parallel_For() => Parallel.For(0, _array.Length, i => _array[i] += 2);

        [Benchmark(Baseline = true)]
        public void ParallelHelper_ForEach() => ParallelHelper.ForEach<double, AddTwo>(_array);

        private readonly struct AddTwo : IRefAction<double> {
            public void Invoke(ref double x) => x += 2;
        }
    }

}