simlib/Random.java at main · jumunozle/simlib · GitHub

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public class Random
{
	private static final int MULT1 = 24112;
	private static final int MULT2 = 26143;
	private static final int B2E15 = 32768; // 2 to 15th power
	private static final int B2E16 = 65536; // 2 to 16th power
	private static final int MODLUS = 2147483647;  // largest integer supported
	private static long zrng[] = {0,
		  1973272912,  281629770,   20006270, 1280689831, 2096730329,
		  1933576050,  913566091,  246780520, 1363774876,  604901985,
		  1511192140, 1259851944,  824064364,  150493284,  242708531,
		    75253171, 1964472944, 1202299975,  233217322, 1911216000,
		   726370533,  403498145,  993232223, 1103205531,  762430696,
		  1922803170, 1385516923,   76271663,  413682397,  726466604,
		   336157058, 1432650381, 1120463904,  595778810,  877722890,
		  1046574445,   68911991, 2088367019,  748545416,  622401386,
		  2122378830,  640690903, 1774806513, 2132545692, 2079249579,
		    78130110,  852776735, 1187867272, 1351423507, 1645973084,
		  1997049139,  922510944, 2045512870,  898585771,  243649545,
		  1004818771,  773686062,  403188473,  372279877, 1901633463,
		   498067494, 2087759558,  493157915,  597104727, 1530940798,
		  1814496276,  536444882, 1663153658,  855503735,   67784357,
		  1432404475,  619691088,  119025595,  880802310,  176192644,
		  1116780070,  277854671, 1366580350, 1142483975, 2026948561,
		  1053920743,  786262391, 1792203830, 1494667770, 1923011392,
		  1433700034, 1244184613, 1147297105,  539712780, 1545929719,
		   190641742, 1645390429,  264907697,  620389253, 1502074852,
		   927711160,  364849192, 2049576050,  638580085,  547070247
		};

	// Note there is no constructor here.  Objects are never instantiated.

	// The next routine supplies a random float on the interval from 0 to 1
	// the input is a stream # from 1 to 100
	public static float rand(int stream)
	{
		long zi, lowprd, hi31;

		zi = zrng[stream];
		lowprd = (zi & 65535) * MULT1;
		hi31 = (zi >> 16) * MULT1 + (lowprd >> 16);
		zi = ((lowprd & 65535) - MODLUS) +
			((hi31 & 32767) << 16) + (hi31 >> 15);
		if (zi < 0) zi += MODLUS;
		lowprd = (zi & 65535) * MULT2;
		hi31 = (zi >> 16) * MULT2 + (lowprd >> 16);
		zi = ((lowprd & 65535) - MODLUS) +
			((hi31 & 32767) << 16) + (hi31 >> 15);
		if (zi < 0) zi += MODLUS;
		zrng[stream] = zi;
		return ((zi >> 7 | 1) + 1)/(float)16777216.0;
	}

	public static void randst(long zset, int stream)
	{
		zrng[stream] = zset;
	}

	public static long randgt(int stream)
	{
		return zrng[stream];
	}


	public static float expon(float rmean, int istrm)
	{
		float u;
		u = rand(istrm);
		return rmean*(float)Math.log(u)*(-1);
	}

	public static int irandi(int nvalue, float probd[], int istrm)
	{
		int randInt = nvalue;
		float u = rand(istrm);
		for (int i = nvalue; i > 0; i--)
		{
			if (u < probd[i])
			{
				randInt = i;
			}
		}
		return randInt;  // This is an indication of an error
	}

	public static float unifrm(float a, float b, int istrm)
	{
		float u;

		u = rand(istrm);
		return a + u*(b-a);
	}

	public static float erlang(int m, float mean, int stream)
	{
		float mean_exponential, sum;

		mean_exponential = mean/m;
		sum = (float)0.0;
		for (int i = 1; i <= m; i++)
			sum += expon(mean_exponential, stream);
		return sum;
	}

	public static int randomInteger(float probDistrib[], int stream)
	{
		float u = rand(stream);
		int retrn = 1;
		for (int i = 1; u >= probDistrib[i]; i++)
			retrn++;
		return retrn;
	}

}