third_party/mt19937ar/mt19937ar.cc

   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 }