EvilLimitRange.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using devDept.Geometry;
using Xunit;
using Xunit.Abstractions;

namespace Weingartner.EyeShot.Spec
{
    public class PerformanceSpec 
    {
        private readonly ITestOutputHelper output;

        public PerformanceSpec(ITestOutputHelper output)
        {
            this.output = output;
        }

        void LimitRange(double a, ref double i, double b)
        {
            if (i < a)
            {
                i = a;
            }else
            if (i > b)
            {
                i = b;
            }

        }

        public interface Ord<T>
        {
            int Compare(T a, T b);
        }

        public struct OrdDouble : Ord<double>
        {
            public int Compare(double a, double b)
            {
                if (a < b)
                    return -1;
                if (a > b)
                    return 1;
                return 0;
            }
        }

        void LimitRangeGeneric<TOrd,T>(T a, ref T i, T b) 
            where TOrd : struct, Ord<T>
        {
            if (default(TOrd).Compare(i,a)<0)
            {
                i = a;
            }else
            if (default(TOrd).Compare( i,b )>0)
            {
                i = b;
            }
        }

        [Fact]
        public void LimitRangeIsEvil()
        {
            var s = Stopwatch.StartNew();
            var sum = 0.0;
            for (int i = 0; i < 1000000; i++)
            {
                var value = (double) i;
                Utility.LimitRange( -1, ref value, 1);
                sum += value;
            }
            output.WriteLine( $"Evil time = {s.ElapsedMilliseconds}" );
            output.WriteLine( $"Sum = {sum}" );

            sum = 0;
            s = Stopwatch.StartNew();
            for (int i = 0; i < 1000000; i++)
            {
                var value = (double) i;
                LimitRange( -1, ref value, 1);
                sum += value;
            }
            output.WriteLine( $"Good time = {s.ElapsedMilliseconds}" );
            output.WriteLine( $"Sum = {sum}" );

            sum = 0;
            s = Stopwatch.StartNew();
            for (int i = 0; i < 1000000; i++)
            {
                var value = (double) i;
                LimitRangeGeneric<OrdDouble,double>( -1, ref value, 1);
                sum += value;
            }
            output.WriteLine( $"Generic time = {s.ElapsedMilliseconds}" );
            output.WriteLine( $"Sum = {sum}" );
        }
    }
}

Result.txt

Evil time = 32
Sum = 999999
Good time = 1
Sum = 999999
Generic time = 1
Sum = 999999