Using SSE in c# is it possible?

Question

I was reading a question about c# code optimization and one solution was to use c++ with SSE. Is it possible to do SSE directly from a c# program?

Answer 1

Modern C# Supports SIMD/SSE instructions well and makes them fairly simple to use. Not all instructions are yet supported.

Here is an example of an SSE .Sum() of an array of uint[]:

    using System.Numerics;

    private static ulong SumSseInner(this uint[] arrayToSum, int l, int r)
    {
        var sumVectorLower = new Vector();
        var sumVectorUpper = new Vector();
        var longLower      = new Vector();
        var longUpper      = new Vector();
        int sseIndexEnd = l + ((r - l + 1) / Vector.Count) * Vector.Count;
        int i;
        for (i = l; i < sseIndexEnd; i += Vector.Count)
        {
            var inVector = new Vector(arrayToSum, i);
            Vector.Widen(inVector, out longLower, out longUpper);
            sumVectorLower += longLower;
            sumVectorUpper += longUpper;
        }
        ulong overallSum = 0;
        for (; i <= r; i++)
            overallSum += arrayToSum[i];
        sumVectorLower += sumVectorUpper;
        for (i = 0; i < Vector.Count; i++)
            overallSum += sumVectorLower[i];
        return overallSum;
    }

This particular function is part of an open source and free nuget package, HPCsharp, available on nuget.org, which I maintain.