using System;

using System.Numerics;

using System.Security.Cryptography;

using System.Text;

using System.Threading;

​

namespace TestAb

{

    class Program

    {

        static void Main(string[] args)

        {

            Test64();

            Test128();

        }

​

        private static void Test64()

        {

            int a = 0;

            int b = 0;

            for (int i = 0; i < 100_000_000; i++)

            {

                if (ComputeFeatureValue64(Guid.NewGuid().ToString()) == 0)

                {

                    a++;

                }

                else

                {

                    b++;

                }

            }

​

            Console.WriteLine($"64bit: a: {a}, b:{b}");

        }

​

        private static void Test128()

        {

            int a = 0;

            int b = 0;

            for (int i = 0; i < 100_000_000; i++)

            {

                if (ComputeFeatureValue(Guid.NewGuid().ToString()) == 0)

                {

                    a++;

                }

                else

                {

                    b++;

                }

            }

​

            Console.WriteLine($"128bit: a: {a}, b:{b}");

        }

​

        private static readonly ThreadLocal<MD5> ThreadMd5 = new ThreadLocal<MD5>(MD5.Create);

​

        private static int ComputeFeatureValue64(string userId)

        {

            var input = $"{userId}123";

            var inputHash = ThreadMd5.Value.ComputeHash(Encoding.UTF8.GetBytes(input));

​

            var featureValue = (byte)BigInteger.Abs(new BigInteger(inputHash) % new BigInteger(100) + 1);

            return featureValue > 50 ? 0 : 1;

        }

​

        private static byte ComputeFeatureValue(string userId)

        {

            var input = $"{userId}123";

            var inputHash = ThreadMd5.Value.ComputeHash(Encoding.UTF8.GetBytes(input));

​

            var featureValue = (float)(new BigInteger(inputHash, true) % 100);

​

            return featureValue + 1f > 50 ? (byte)0 : (byte)1;

        }

    }

}

​