MT19937.cs

using System;
// ORIGNAL COMMENTS
/* 
   A C-program for MT19937, with initialization improved 2002/1/26.
   Coded by Takuji Nishimura and Makoto Matsumoto.

   Before using, initialize the state by using init_genrand(seed)  
   or init_by_array(init_key, key_length).

   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
   All rights reserved.                          

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.

     3. The names of its contributors may not be used to endorse or promote 
        products derived from this software without specific prior written 
        permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


   Any feedback is very welcome.
   http://www.math.keio.ac.jp/matumoto/emt.html
   email: matumoto@math.keio.ac.jp
*/
// Converted to C# 

namespace MersenneTwister
{
	/// <summary>
	/// Summary description for MT19937.
	/// </summary>
	public class MT19937
	{
		// Period parameters
		private const ulong	N				= 624;
		private const ulong	M				= 397;
		private const ulong	MATRIX_A		= 0x9908B0DFUL;		// constant vector a 
		private const ulong UPPER_MASK		= 0x80000000UL;		// most significant w-r bits
		private const ulong LOWER_MASK		= 0X7FFFFFFFUL;		// least significant r bits
		private const uint	DEFAULT_SEED	= 4357;

		private static ulong [] mt			= new ulong[N+1];	// the array for the state vector
		private static ulong	mti			= N + 1;			// mti==N+1 means mt[N] is not initialized

		public MT19937()
		{
			ulong [] init = new ulong[4];
			init[0]= 0x123;
			init[1]= 0x234;
			init[2]= 0x345;
			init[3] =0x456;
			ulong length = 4;
			init_by_array(init, length);
		}

		// initializes mt[N] with a seed
		public void init_genrand(ulong s)
		{
			mt[0]= s & 0xffffffffUL;
            mti=1;
			while (mti < N)
			{
				mt[mti] = (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 
				/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
				/* In the previous versions, MSBs of the seed affect   */
				/* only MSBs of the array mt[].                        */
				/* 2002/01/09 modified by Makoto Matsumoto             */
				mt[mti] &= 0xffffffffUL;
				/* for >32 bit machines */
                mti++;
			}
		}


		// initialize by an array with array-length
		// init_key is the array for initializing keys
		// key_length is its length
		public void init_by_array(ulong[] init_key, ulong key_length)
		{
			ulong i, j, k;
			init_genrand(19650218UL);
			i=1; j=0;
			k = (N > key_length ? N : key_length);
			while (k > 0) 
			{
				mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
				+ init_key[j] + j;		// non linear 
				mt[i] &= 0xffffffffUL;	// for WORDSIZE > 32 machines
				i++; j++;
				if (i>=N) { mt[0] = mt[N-1]; i=1; }
				if (j>=key_length) j=0;
                k--;
			}
            k = N - 1;
			while (k > 0) 
			{
				mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
				- i;					// non linear
				mt[i] &= 0xffffffffUL;	// for WORDSIZE > 32 machines
				i++;
				if (i>=N) { mt[0] = mt[N-1]; i=1; }
                k--;
			}
			mt[0] = 0x80000000UL;		// MSB is 1; assuring non-zero initial array
		}

		// generates a random number on [0,0x7fffffff]-interval
		public long genrand_int31()
		{
			return (long)(genrand_int32()>>1);
		}
		/// <summary>
        /// generates a random number on [0,1]-real-interval
		/// </summary>
		/// <returns></returns>
		public double genrand_real1()
		{
			return (double)genrand_int32() / 4294967295.0; // divided by 2^32-1 
		}
		/// <summary>
        /// generates a random number on [0,1)-real-interval
		/// </summary>
		/// <returns></returns>
		public double genrand_real2()
		{
			return (double)genrand_int32() / 4294967296.0; // divided by 2^32
		}
		/// <summary>
        /// generates a random number on (0,1)-real-interval
		/// </summary>
		/// <returns></returns>
		public double genrand_real3()
		{
			return (((double)genrand_int32()) + 0.5) / 4294967296.0; // divided by 2^32
		}
		// generates a random number on [0,1) with 53-bit resolution
		public double genrand_res53() 
		{ 
			ulong a = genrand_int32() >>5;
			ulong b = genrand_int32()>>6; 
			return(double)(a*67108864.0+b)*(1.0/9007199254740992.0); 
		} 
		// These real versions are due to Isaku Wada, 2002/01/09 added 
		
		// generates a random number on [0,0xffffffff]-interval
		public ulong genrand_int32()
		{
			ulong y = 0;
			ulong [] mag01 = new ulong[2];
			mag01[0]	= 0x0UL;
			mag01[1]	= MATRIX_A;
			/* mag01[x] = x * MATRIX_A  for x=0,1 */

			if (mti >= N) 
			{ 
				// generate N words at one time
				ulong kk;

				if (mti == N+1)   /* if init_genrand() has not been called, */
					init_genrand(5489UL); /* a default initial seed is used */
                kk=0;
				while (kk < N - M)
				{
					y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
					mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
                    kk++;
				}
				while (kk < N-1)
				{
					y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
					//mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
					mt[kk] = mt[kk - 227] ^ (y >> 1) ^ mag01[y & 0x1UL];
                    kk++;
				}
				y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
				mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];

				mti = 0;
			}
		  
			y = mt[mti++];

			/* Tempering */
			y ^= (y >> 11);
			y ^= (y << 7) & 0x9d2c5680UL;
			y ^= (y << 15) & 0xefc60000UL;
			y ^= (y >> 18);

			return y;
		}
	}
}