File: random.h

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/*
 * This file is part of din.
 *
 * din is copyright (c) 2006 - 2012 S Jagannathan <jag@dinisnoise.org>
 * For more information, please visit http://dinisnoise.org
 *
 * din is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * din is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with din.  If not, see <http://www.gnu.org/licenses/>.
 *
*/
#ifndef ___random
#define ___random

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

const int N = 624;
const int M = 397;
const unsigned int MATRIX_A = 0x9908b0df; /* constant vector a */
const unsigned int UPPER_MASK = 0x80000000; /* most significant w-r bits */
const unsigned int LOWER_MASK = 0x7fffffff; /* least significant r bits */

static unsigned int mt[N]; /* the array for the state vector  */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */

/* initializes mt[N] with a seed */
inline void seed_rand_gen (unsigned int s)
{
    mt[0]= s & 0xffffffff;
    for (mti=1; mti<N; mti++) {
        mt[mti] =
      (1812433253 * (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] &= 0xffffffff;
        /* for >32 bit machines */
    }
}

inline unsigned int get_rand_32 (void)
{
    unsigned int y;
    static unsigned int mag01[2]={0x0, MATRIX_A};
    /* mag01[x] = x * MATRIX_A  for x=0,1 */

    if (mti >= N) { /* generate N words at one time */
        int kk, nm=N-M, mn=-nm, n1=N-1, m1=M-1;

        if (mti == N+1)   /* if init_gen_rand_() has not been called, */
           seed_rand_gen (0);

        for (kk=0;kk<nm;kk++) {
            y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
            mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
        }
        for (;kk<n1;kk++) {
            y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
            mt[kk] = mt[kk+mn] ^ (y >> 1) ^ mag01[y & 0x1];
        }
        y = (mt[n1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
        mt[n1] = mt[m1] ^ (y >> 1) ^ mag01[y & 0x1];

        mti = 0;
    }

    y = mt[mti++];

    /* Tempering */
    y ^= (y >> 11);
    y ^= (y << 7) & 0x9d2c5680;
    y ^= (y << 15) & 0xefc60000;
    y ^= (y >> 18);

    return y;

}

inline unsigned int get_rand_16 (void) {
  return get_rand_32()&0xffff;
}

inline unsigned int get_rand_8 (void) {
  return get_rand_32()&0xff;
}

inline unsigned int get_rand_7 (void) {
  return get_rand_32()&0x7f;
}

inline unsigned int get_rand_bit (void) {
  return get_rand_32()&0x01;
}

inline double get_rand_01 (void) {
  return (get_rand_16() * 1.0 / 0xffff);
}

template<typename T> class rnd {

  T min, max;
  T delta;

  public:
    rnd (T mi, T ma) {
      min = mi;
      max = ma;
      delta = max - min;
    }
    T operator() () {
      return (T) (min + delta * get_rand_01());
    }
};

#endif