LoadsPerCycleTest

LoadsPerCycleTest.cs

   public class CpuLoadLimitTests
    {
        private readonly int[] _data = new int[100_000_000];

        [Benchmark(Baseline = true)]
        public unsafe int Sum_Simple()
        {
            var s0 = 0;
            var s1 = 0;
            var s2 = 0;
            var s3 = 0;

            fixed (int* data = &_data[0])
            {
                for (var i = 0; i < _data.Length; i += 4)
                {
                    var p = &data[i];

                    s0 += p[0];
                    s1 += p[1];
                    s2 += p[2];
                    s3 += p[3];
                }

                return s0 + s1 + s2 + s3;
            }
        }

        [Benchmark]
        public unsafe int Sum_Tricky()
        {
            var s0 = 0;
            var s1 = 0;
            var s2 = 0;
            var s3 = 0;

            fixed (int* data = &_data[0])
            {
                for (var i = 0; i < _data.Length; i += 4)
                {
                    var p = (long*)data;
                    var f = *p;
                    var s = *p + 1;
 
                    s0 += (int)(f >> 32);
                    s1 += (int)(f & 0xFFFF_FFFF);
                    s2 += (int)(s >> 32);
                    s3 += (int)(s & 0xFFFF_FFFF);

                    p += 2;
                }

                return s0 + s1 + s2 + s3;
            }
        }
    }