// See https://habr.com/ru/companies/skbkontur/articles/737858/

​

using System;

using System.Diagnostics;

using System.Linq;

using System.Numerics;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello");

        Console.WriteLine();

​

        Console.WriteLine($"Vector<byte>.IsSupported = {Vector<byte>.IsSupported}");

        Console.WriteLine($"Vector<sbyte>.IsSupported = {Vector<sbyte>.IsSupported}");

        Console.WriteLine($"Vector<short>.IsSupported = {Vector<short>.IsSupported}");

        Console.WriteLine($"Vector<ushort>.IsSupported = {Vector<ushort>.IsSupported}");

        Console.WriteLine($"Vector<int>.IsSupported = {Vector<int>.IsSupported}");

        Console.WriteLine($"Vector<uint>.IsSupported = {Vector<uint>.IsSupported}");

        Console.WriteLine($"Vector<long>.IsSupported = {Vector<long>.IsSupported}");

        Console.WriteLine($"Vector<ulong>.IsSupported = {Vector<ulong>.IsSupported}");

        Console.WriteLine($"Vector<Int128>.IsSupported = {Vector<Int128>.IsSupported}");

        Console.WriteLine($"Vector<UInt128>.IsSupported = {Vector<UInt128>.IsSupported}");

        Console.WriteLine($"Vector<nint>.IsSupported = {Vector<nint>.IsSupported}");

        Console.WriteLine($"Vector<nuint>.IsSupported = {Vector<nuint>.IsSupported}");

        Console.WriteLine($"nint.Size = {nint.Size}");

        Console.WriteLine();

        Console.WriteLine($"Is64BitOperatingSystem = {Environment.Is64BitOperatingSystem}");

        Console.WriteLine($"Is64BitProcess = {Environment.Is64BitProcess}");

        Console.WriteLine($"ProcessorCount = {Environment.ProcessorCount}");

        Console.WriteLine($"OSVersion = {Environment.OSVersion}");

        Console.WriteLine($".NET Version = {Environment.Version}");

        Console.WriteLine();

​

        Console.WriteLine($"Vector<long>.IsSupported = {Vector<long>.IsSupported}");

        Console.WriteLine($"Vector.IsHardwareAccelerated = {Vector.IsHardwareAccelerated}");

        Console.WriteLine($"Vector<long>.Count = {Vector<long>.Count}");

        Console.WriteLine();

​

        //var array = new long[16_000];

        var array = new long[1_600_000];

        {

            var random = new Random();

            for(var i = 0; i < array.Length; i++)

                array[i] = random.Next(100);

        }

        long sum = 0;

        var repeat = 100;

        {

            for(var r = 0; r < repeat; r++)

                sum = array.Sum();

            Stopwatch stopwatch = new Stopwatch();

            stopwatch.Start();

            for(var r = 0; r < repeat; r++)

                sum = array.Sum();

            stopwatch.Stop();

​

            Console.WriteLine($"Sum = {sum} for {stopwatch.ElapsedTicks:n0} ticks");

        }

        {

            for(var r = 0; r < repeat; r++)

                sum = SumSimd(array);

​

            Stopwatch stopwatch = new Stopwatch();

            stopwatch.Start();

            for(var r = 0; r < repeat; r++)

                sum = SumSimd(array);

            stopwatch.Stop();

​

            Console.WriteLine($"SumSimd = {sum} for {stopwatch.ElapsedTicks:n0} ticks");

        }

        {

            for(var r = 0; r < repeat; r++)

                sum = SumSimdParallel(array);

​

            Stopwatch stopwatch = new Stopwatch();

            stopwatch.Start();

            for(var r = 0; r < repeat; r++)

                sum = SumSimdParallel(array);

            stopwatch.Stop();

            Console.WriteLine($"SumSimdParallel = {sum} for {stopwatch.ElapsedTicks:n0} ticks");

        }

​

        Console.WriteLine("Goodbye");

    }

    public static long SumSimd(long[] array)

    {

        var vectorSize = Vector<long>.Count;

​

        var vectorSum = new Vector<long>(array);

        var span = array.AsSpan(vectorSize);

        while (span.Length >= vectorSize)

        {

            vectorSum += new Vector<long>(span);

            span = span.Slice(vectorSize);

        }

        return Vector.Dot(vectorSum, Vector<long>.One);

    }   

​

    public static long SumSimdParallel(long[] array)

    {

        var degreeOfParallelism = Math.Max(Vector<long>.Count, (int)BitOperations.RoundUpToPowerOf2((uint)Environment.ProcessorCount));

        var sums = new long[degreeOfParallelism];

        var len = array.Length / degreeOfParallelism;

        //Console.WriteLine($"degreeOfParallelism = {degreeOfParallelism}");

        //Console.WriteLine($"len = {len}");

        //Console.WriteLine($"Count = {Vector<long>.Count}");

​

        Parallel.For(0, degreeOfParallelism, idx =>

        {

            var vectorSize = Vector<long>.Count;

            var span = array.AsSpan(idx * len, len);

            var vectorSum = new Vector<long>(span);

            span = span.Slice(vectorSize);

            while (span.Length >= vectorSize)

            {

                vectorSum += new Vector<long>(span);

                span = span.Slice(vectorSize);

            }

            sums[idx] = Vector.Dot(vectorSum, Vector<long>.One);

        });

        return SumSimd(sums);

        //return -1;

    }   

}