MinFt/Client/Assets/Scripts/Tools/Beta.cs

namespace System
{
    public class Beta
    {
        //[UnityEditor.MenuItem("Tools/TestBeta")]
        //void TestBeta()
        //{
        //    List<double> doubles = new List<double>();
        //    for (int i = 0; i < 10000; i++)
        //    {
        //        doubles.Add(Beta.Sample(100, 900));
        //    }
        //    doubles.Sort();
        //    for (int i = 0; i < doubles.Count; i++)
        //    {
        //        int s = (int)(doubles[i] * 100);
        //        Debug.Log(s);
        //    }
        //}
        static double GammaSampleUnchecked(System.Random rnd, double shape, double rate)
        {
            if (double.IsPositiveInfinity(rate))
            {
                return shape;
            }

            double num = shape;
            double num2 = 1.0;
            if (shape < 1.0)
            {
                num = shape + 1.0;
                num2 = System.Math.Pow(rnd.NextDouble(), 1.0 / shape);
            }

            double num3 = num - 1.0 / 3.0;
            double num4 = 1.0 / System.Math.Sqrt(9.0 * num3);
            double num6;
            double num7;
            double num5;
            do
            {
                num5 = NormalSampleUnchecked(rnd, 0.0, 1.0);
                for (num6 = 1.0 + num4 * num5; num6 <= 0.0; num6 = 1.0 + num4 * num5)
                {
                    num5 = NormalSampleUnchecked(rnd, 0.0, 1.0);
                }

                num6 = num6 * num6 * num6;
                num7 = rnd.NextDouble();
                num5 *= num5;
                if (num7 < 1.0 - 0.0331 * num5 * num5)
                {
                    return num2 * num3 * num6 / rate;
                }
            }
            while (!(System.Math.Log(num7) < 0.5 * num5 + num3 * (1.0 - num6 + System.Math.Log(num6))));
            return num2 * num3 * num6 / rate;
        }
        static double NormalSampleUnchecked(System.Random rnd, double mean, double stddev)
        {
            double x;
            double y;
            while (!PolarTransform(rnd.NextDouble(), rnd.NextDouble(), out x, out y))
            {
            }

            return mean + stddev * x;
        }
        static bool PolarTransform(double a, double b, out double x, out double y)
        {
            double num = 2.0 * a - 1.0;
            double num2 = 2.0 * b - 1.0;
            double num3 = num * num + num2 * num2;
            if (num3 >= 1.0 || num3 == 0.0)
            {
                x = 0.0;
                y = 0.0;
                return false;
            }

            double num4 = Math.Sqrt(-2.0 * Math.Log(num3) / num3);
            x = num * num4;
            y = num2 * num4;
            return true;
        }
        public static double Sample(double alpha, double beta)
        {
            System.Random rng = new System.Random();
            double num;
            double num2;
            if (alpha == beta)
            {
                num = GammaSampleUnchecked(rng, alpha, 1.0);
                num2 = GammaSampleUnchecked(rng, beta, 1.0);
                if (num == 0.0 && num2 == 0.0)
                {
                    if (rng.NextDouble() < 0.5f)
                    {
                        return 1;
                    }

                    return 0;
                }
            }
            else
            {
                do
                {
                    num = GammaSampleUnchecked(rng, alpha, 1.0);
                    num2 = GammaSampleUnchecked(rng, beta, 1.0);
                }
                while (num == 0.0 && num2 == 0.0);
            }

            return num / (num + num2);
        }
    }
}