using System;
using System.Diagnostics;

namespace fastexponent
{
	class Program
	{
		static double[] ExpAdjustment = new double[256] {
			1.040389835,
			1.039159306,
			1.037945888,
			1.036749401,
			1.035569671,
			1.034406528,
			1.033259801,
			1.032129324,
			1.031014933,
			1.029916467,
			1.028833767,
			1.027766676,
			1.02671504,
			1.025678708,
			1.02465753,
			1.023651359,
			1.022660049,
			1.021683458,
			1.020721446,
			1.019773873,
			1.018840604,
			1.017921503,
			1.017016438,
			1.016125279,
			1.015247897,
			1.014384165,
			1.013533958,
			1.012697153,
			1.011873629,
			1.011063266,
			1.010265947,
			1.009481555,
			1.008709975,
			1.007951096,
			1.007204805,
			1.006470993,
			1.005749552,
			1.005040376,
			1.004343358,
			1.003658397,
			1.002985389,
			1.002324233,
			1.001674831,
			1.001037085,
			1.000410897,
			0.999796173,
			0.999192819,
			0.998600742,
			0.998019851,
			0.997450055,
			0.996891266,
			0.996343396,
			0.995806358,
			0.995280068,
			0.99476444,
			0.994259393,
			0.993764844,
			0.993280711,
			0.992806917,
			0.992343381,
			0.991890026,
			0.991446776,
			0.991013555,
			0.990590289,
			0.990176903,
			0.989773325,
			0.989379484,
			0.988995309,
			0.988620729,
			0.988255677,
			0.987900083,
			0.987553882,
			0.987217006,
			0.98688939,
			0.98657097,
			0.986261682,
			0.985961463,
			0.985670251,
			0.985387985,
			0.985114604,
			0.984850048,
			0.984594259,
			0.984347178,
			0.984108748,
			0.983878911,
			0.983657613,
			0.983444797,
			0.983240409,
			0.983044394,
			0.982856701,
			0.982677276,
			0.982506066,
			0.982343022,
			0.982188091,
			0.982041225,
			0.981902373,
			0.981771487,
			0.981648519,
			0.981533421,
			0.981426146,
			0.981326648,
			0.98123488,
			0.981150798,
			0.981074356,
			0.981005511,
			0.980944219,
			0.980890437,
			0.980844122,
			0.980805232,
			0.980773726,
			0.980749562,
			0.9807327,
			0.9807231,
			0.980720722,
			0.980725528,
			0.980737478,
			0.980756534,
			0.98078266,
			0.980815817,
			0.980855968,
			0.980903079,
			0.980955475,
			0.981017942,
			0.981085714,
			0.981160303,
			0.981241675,
			0.981329796,
			0.981424634,
			0.981526154,
			0.981634325,
			0.981749114,
			0.981870489,
			0.981998419,
			0.982132873,
			0.98227382,
			0.982421229,
			0.982575072,
			0.982735318,
			0.982901937,
			0.983074902,
			0.983254183,
			0.983439752,
			0.983631582,
			0.983829644,
			0.984033912,
			0.984244358,
			0.984460956,
			0.984683681,
			0.984912505,
			0.985147403,
			0.985388349,
			0.98563532,
			0.98588829,
			0.986147234,
			0.986412128,
			0.986682949,
			0.986959673,
			0.987242277,
			0.987530737,
			0.987825031,
			0.988125136,
			0.98843103,
			0.988742691,
			0.989060098,
			0.989383229,
			0.989712063,
			0.990046579,
			0.990386756,
			0.990732574,
			0.991084012,
			0.991441052,
			0.991803672,
			0.992171854,
			0.992545578,
			0.992924825,
			0.993309578,
			0.993699816,
			0.994095522,
			0.994496677,
			0.994903265,
			0.995315266,
			0.995732665,
			0.996155442,
			0.996583582,
			0.997017068,
			0.997455883,
			0.99790001,
			0.998349434,
			0.998804138,
			0.999264107,
			0.999729325,
			1.000199776,
			1.000675446,
			1.001156319,
			1.001642381,
			1.002133617,
			1.002630011,
			1.003131551,
			1.003638222,
			1.00415001,
			1.004666901,
			1.005188881,
			1.005715938,
			1.006248058,
			1.006785227,
			1.007327434,
			1.007874665,
			1.008426907,
			1.008984149,
			1.009546377,
			1.010113581,
			1.010685747,
			1.011262865,
			1.011844922,
			1.012431907,
			1.013023808,
			1.013620615,
			1.014222317,
			1.014828902,
			1.01544036,
			1.016056681,
			1.016677853,
			1.017303866,
			1.017934711,
			1.018570378,
			1.019210855,
			1.019856135,
			1.020506206,
			1.02116106,
			1.021820687,
			1.022485078,
			1.023154224,
			1.023828116,
			1.024506745,
			1.025190103,
			1.02587818,
			1.026570969,
			1.027268461,
			1.027970647,
			1.02867752,
			1.029389072,
			1.030114973,
			1.030826088,
			1.03155163,
			1.032281819,
			1.03301665,
			1.033756114,
			1.034500204,
			1.035248913,
			1.036002235,
			1.036760162,
			1.037522688,
			1.038289806,
			1.039061509,
			1.039837792,
			1.040618648
		};

		static double FastExp(double x)
		{
			var tmp = (long)(1512775 * x + 1072632447);
			int index = (int)(tmp >> 12) & 0xFF;
			return BitConverter.Int64BitsToDouble(tmp << 32) * ExpAdjustment[index];
		}

		static void Main(string[] args)
		{
			double[] x = new double[1000000];
			double[] ex = new double[x.Length];
			double[] fx = new double[x.Length];
			Random r = new Random();
			for (int i = 0; i < x.Length; ++i)
				x[i] = r.NextDouble() * 40;

			Stopwatch sw = new Stopwatch();
			sw.Start();
			for (int j = 0; j < x.Length; ++j)
				ex[j] = Math.Exp(x[j]);
			sw.Stop();
			double builtin = sw.Elapsed.TotalMilliseconds;
			sw.Reset();
			sw.Start();
			for (int k = 0; k < x.Length; ++k)
				fx[k] = FastExp(x[k]);
			sw.Stop();
			double custom = sw.Elapsed.TotalMilliseconds;

			double min = 1, max = 1;
			for (int m = 0; m < x.Length; ++m) {
				double ratio = fx[m] / ex[m];
				if (min > ratio) min = ratio;
				if (max < ratio) max = ratio;
			}

			Console.WriteLine("minimum ratio = " + min.ToString() + ", maximum ratio = " + max.ToString() + ", speedup = " + (builtin / custom).ToString());
		 }
	}
}