VectorizedQueryTest.cs

using System;
using System.Diagnostics;
using Mono.Simd;

namespace VectorizedQueryTest
{
    class Program
    {
        static void Main(string[] args)
        {
            // SELECT * FROM Table WHERE ColumnA < ColumnB
            int rowCount = 10000000; // 10M
            var rand = new Random();
            var rowids = new int[rowCount];
            var columna = new int[rowids.Length];
            var columnb = new int[rowids.Length];
            var result = new int[rowids.Length + 1];
            var pos = 0;

            for (int i = 0; i < rowids.Length; i++)
            {
                rowids[i] = i;
                columna[i] = rand.Next();
                columnb[i] = rand.Next();
            }

            // Start of performance measuring.
            var watch = new Stopwatch();
            watch.Start();

            var columnbVector = new Vector4i();
            var columnaVector = new Vector4i();
            var rowIdBlock = new int[4];

            for (int i = 0; i < rowids.Length; i += 4)
            {
                columnaVector.X = columna[i];
                columnaVector.Y = columna[i + 1];
                columnaVector.Z = columna[i + 2];
                columnaVector.W = columna[i + 3];

                columnbVector.X = columnb[i];
                columnbVector.Y = columnb[i + 1];
                columnbVector.Z = columnb[i + 2];
                columnbVector.W = columnb[i + 3];

                var mask = columnbVector.CompareGreaterThan(columnaVector);
                // To compare greater than or equals, compare equals, compare greater than, and then and the two masks together. Use bitwise OR.

                rowIdBlock[0] = rowids[i];
                rowIdBlock[1] = rowids[i + 1];
                rowIdBlock[2] = rowids[i + 2];
                rowIdBlock[3] = rowids[i + 3];
                SIMD_Process(mask, rowIdBlock, result, ref pos);
            }
            result[pos] = 0;
            watch.Stop(); // 197 milliseconds to process 10M rows.

            Debug.WriteLine(watch.Elapsed);
            Console.WriteLine(watch.Elapsed);
            Console.ReadKey();
        }

        public static void SIMD_Process(Vector4i mask, int[] rowids, int[] result, ref int pos)
        {
            if ((mask.X | mask.Y | mask.Z | mask.W) == 0) return;

            const int S = 4;
            
            for (int j = 0; j < S; j++)
            {
                var tmp = mask[j] & 1;
                result[pos] = rowids[j];
                pos += tmp;
            }
        }
    }
}