src/mersenne.cpp

   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 "types.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 static unsigned long mt[N]; /* the array for the state vector  */
  54 static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */
  55
  56 /* initializes mt[N] with a seed */
  57 void init_genrand(unsigned long s)
  58 {
  59     mt[0]= s & 0xffffffffUL;
  60     for (mti=1; mti<N; mti++) {
  61         mt[mti] =
  62             (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
  63         /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
  64         /* In the previous versions, MSBs of the seed affect   */
  65         /* only MSBs of the array mt[].                        */
  66         /* 2002/01/09 modified by Makoto Matsumoto             */
  67         mt[mti] &= 0xffffffffUL;
  68         /* for >32 bit machines */
  69     }
  70 }
  71
  72 /* initialize by an array with array-length */
  73 /* init_key is the array for initializing keys */
  74 /* key_length is its length */
  75 /* slight change for C++, 2004/2/26 */
  76 void init_by_array(unsigned long init_key[], int key_length)
  77 {
  78     int i, j, k;
  79     init_genrand(19650218UL);
  80     i=1; j=0;
  81     k = (N>key_length ? N : key_length);
  82     for (; k; k--) {
  83         mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
  84           + init_key[j] + j; /* non linear */
  85         mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
  86         i++; j++;
  87         if (i>=N) { mt[0] = mt[N-1]; i=1; }
  88         if (j>=key_length) j=0;
  89     }
  90     for (k=N-1; k; k--) {
  91         mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
  92           - i; /* non linear */
  93         mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
  94         i++;
  95         if (i>=N) { mt[0] = mt[N-1]; i=1; }
  96     }
  97
  98     mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
  99 }
 100
 101 /* generates a random number on [0,0xffffffff]-interval */
 102 uint32_t genrand_int32(void) {
 103   unsigned long y;
 104   static unsigned long mag01[2]={0x0UL, MATRIX_A};
 105   /* mag01[x] = x * MATRIX_A  for x=0,1 */
 106
 107   if (mti >= N) { /* generate N words at one time */
 108     int kk;
 109
 110     if (mti == N+1)   /* if init_genrand() has not been called, */
 111       init_genrand(5489UL); /* a default initial seed is used */
 112
 113     for (kk=0;kk<N-M;kk++) {
 114       y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
 115       mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
 116     }
 117     for (;kk<N-1;kk++) {
 118       y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
 119       mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
 120     }
 121     y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
 122     mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];
 123
 124     mti = 0;
 125   }
 126
 127   y = mt[mti++];
 128
 129   /* Tempering */
 130   y ^= (y >> 11);
 131   y ^= (y << 7) & 0x9d2c5680UL;
 132   y ^= (y << 15) & 0xefc60000UL;
 133   y ^= (y >> 18);
 134
 135   return y;
 136 }
 137
 138 uint64_t genrand_int64(void) {
 139   uint64_t x, y;
 140
 141   x = genrand_int32(); y = genrand_int32();
 142   return (x<<32)|y;
 143 }
 144
 145 void init_mersenne(void) {
 146   unsigned long init[4]={0x123, 0x234, 0x345, 0x456}, length=4;
 147   init_by_array(init, length);
 148 }