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      1 /*
      2    A C-program for MT19937, with initialization improved 2002/1/26.
      3    Coded by Takuji Nishimura and Makoto Matsumoto.
      4 
      5    Before using, initialize the state by using init_genrand(seed)
      6    or init_by_array(init_key, key_length).
      7 
      8    Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
      9    All rights reserved.
     10 
     11    Redistribution and use in source and binary forms, with or without
     12    modification, are permitted provided that the following conditions
     13    are met:
     14 
     15      1. Redistributions of source code must retain the above copyright
     16         notice, this list of conditions and the following disclaimer.
     17 
     18      2. Redistributions in binary form must reproduce the above copyright
     19         notice, this list of conditions and the following disclaimer in the
     20         documentation and/or other materials provided with the distribution.
     21 
     22      3. The names of its contributors may not be used to endorse or promote
     23         products derived from this software without specific prior written
     24         permission.
     25 
     26    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     27    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     28    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     29    A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
     30    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     31    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     32    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     33    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     34    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     35    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     36    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     37 
     38 
     39    Any feedback is very welcome.
     40    http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
     41    email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
     42 */
     43 
     44 #include "mt19937ar.h"
     45 
     46 /* Period parameters */
     47 #define N 624
     48 #define M 397
     49 #define MATRIX_A 0x9908b0dfUL   /* constant vector a */
     50 #define UPPER_MASK 0x80000000UL /* most significant w-r bits */
     51 #define LOWER_MASK 0x7fffffffUL /* least significant r bits */
     52 
     53 MersenneTwister::MersenneTwister() : mt(N), mti(N+1) {
     54 }
     55 
     56 MersenneTwister::~MersenneTwister() {
     57 }
     58 
     59 /* initializes mt[N] with a seed */
     60 void MersenneTwister::init_genrand(uint32 s)
     61 {
     62     mt[0]= s & 0xffffffffUL;
     63     for (mti=1; mti<N; mti++) {
     64         mt[mti] =
     65 	    (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
     66         /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
     67         /* In the previous versions, MSBs of the seed affect   */
     68         /* only MSBs of the array mt[].                        */
     69         /* 2002/01/09 modified by Makoto Matsumoto             */
     70         mt[mti] &= 0xffffffffUL;
     71         /* for >32 bit machines */
     72     }
     73 }
     74 
     75 /* initialize by an array with array-length */
     76 /* init_key is the array for initializing keys */
     77 /* key_length is its length */
     78 /* slight change for C++, 2004/2/26 */
     79 void MersenneTwister::init_by_array(uint32 init_key[], int key_length)
     80 {
     81     int i, j, k;
     82     init_genrand(19650218UL);
     83     i=1; j=0;
     84     k = (N>key_length ? N : key_length);
     85     for (; k; k--) {
     86         mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
     87           + init_key[j] + j; /* non linear */
     88         mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
     89         i++; j++;
     90         if (i>=N) { mt[0] = mt[N-1]; i=1; }
     91         if (j>=key_length) j=0;
     92     }
     93     for (k=N-1; k; k--) {
     94         mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
     95           - i; /* non linear */
     96         mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
     97         i++;
     98         if (i>=N) { mt[0] = mt[N-1]; i=1; }
     99     }
    100 
    101     mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
    102 }
    103 
    104 /* generates a random number on [0,0xffffffff]-interval */
    105 uint32 MersenneTwister::genrand_int32(void)
    106 {
    107     uint32 y;
    108     static uint32 mag01[2]={0x0UL, MATRIX_A};
    109     /* mag01[x] = x * MATRIX_A  for x=0,1 */
    110 
    111     if (mti >= N) { /* generate N words at one time */
    112         int kk;
    113 
    114         if (mti == N+1)   /* if init_genrand() has not been called, */
    115             init_genrand(5489UL); /* a default initial seed is used */
    116 
    117         for (kk=0;kk<N-M;kk++) {
    118             y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
    119             mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
    120         }
    121         for (;kk<N-1;kk++) {
    122             y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
    123             mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
    124         }
    125         y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
    126         mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];
    127 
    128         mti = 0;
    129     }
    130 
    131     y = mt[mti++];
    132 
    133     /* Tempering */
    134     y ^= (y >> 11);
    135     y ^= (y << 7) & 0x9d2c5680UL;
    136     y ^= (y << 15) & 0xefc60000UL;
    137     y ^= (y >> 18);
    138 
    139     return y;
    140 }
    141