Pollard’s Rho factoring algorithm in C#

Pollard’s rho algorithm is used to factor composite integers. Suppose you have 8633, 89 *97 are the factors.

Here is the code:

static void Main(string[] args)

        {

            Int64 a = p.PollardRho(12187823);

        }

        public Int64 customFunct(Int64 param, Int64 mod)//Custom number generator

        {

            return ((param * param + 1 )% mod);

        }

        public Int64 PollardRho(Int64 number)

        {

            Int64 a = 2, b = 2, tmp;//initail starting values

            while(true)

            {

            a = customFunct(a,number);//get first number

            b = customFunct(customFunct(b,number),number);//get second double run custom func

            tmp = GCD(Math.Abs(b-a), number);// if a =  b mod d(divisor one of the divisors of our number) then a-b is multiple of d and number is multiple of d 

            if (tmp > 1)

                break;

            }

            return tmp;

        }

        public Int64 GCD(Int64 x, Int64 y)//Greatest Common Divisor

        {

            if (x == 0)//Find it? return

                return y;

            if (y == 0)//Find it? return

                return x;

            x = x % y;// take the mod of the large val to small one if the order is wrong in the next recursive loop it will be correct

            return GCD(y, x);//Parameters changed place

        }

I put comments on the code and included usage.The code includes a custom function you may experiment with and a greatest common divisor calculator.