missing/mt19937.c

   1 /*
   2 This is based on trimmed version of MT19937.  To get the original version,
   3 contact <http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html>.
   4
   5 The original copyright notice follows.
   6
   7    A C-program for MT19937, with initialization improved 2002/2/10.
   8    Coded by Takuji Nishimura and Makoto Matsumoto.
   9    This is a faster version by taking Shawn Cokus's optimization,
  10    Matthe Bellew's simplification, Isaku Wada's real version.
  11
  12    Before using, initialize the state by using init_genrand(mt, seed)
  13    or init_by_array(mt, init_key, key_length).
  14
  15    Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
  16    All rights reserved.
  17
  18    Redistribution and use in source and binary forms, with or without
  19    modification, are permitted provided that the following conditions
  20    are met:
  21
  22      1. Redistributions of source code must retain the above copyright
  23         notice, this list of conditions and the following disclaimer.
  24
  25      2. Redistributions in binary form must reproduce the above copyright
  26         notice, this list of conditions and the following disclaimer in the
  27         documentation and/or other materials provided with the distribution.
  28
  29      3. The names of its contributors may not be used to endorse or promote
  30         products derived from this software without specific prior written
  31         permission.
  32
  33    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  34    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  35    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  36    A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  37    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  38    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  39    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  40    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  41    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  42    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  43    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  44
  45
  46    Any feedback is very welcome.
  47    http://www.math.keio.ac.jp/matumoto/emt.html
  48    email: matumoto@math.keio.ac.jp
  49 */
  50
  51 /* Period parameters */
  52 #define N 624
  53 #define M 397
  54 #define MATRIX_A 0x9908b0dfU    /* constant vector a */
  55 #define UMASK 0x80000000U       /* most significant w-r bits */
  56 #define LMASK 0x7fffffffU       /* least significant r bits */
  57 #define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
  58 #define TWIST(u,v) ((MIXBITS((u),(v)) >> 1) ^ ((v)&1U ? MATRIX_A : 0U))
  59
  60 enum {MT_MAX_STATE = N};
  61
  62 struct MT {
  63     /* assume int is enough to store 32bits */
  64     uint32_t state[N]; /* the array for the state vector  */
  65     uint32_t *next;
  66     int left;
  67 };
  68
  69 #define genrand_initialized(mt) ((mt)->next != 0)
  70 #define uninit_genrand(mt) ((mt)->next = 0)
  71
  72 NO_SANITIZE("unsigned-integer-overflow", static void init_genrand(struct MT *mt, unsigned int s));
  73 NO_SANITIZE("unsigned-integer-overflow", static void init_by_array(struct MT *mt, const uint32_t init_key[], int key_length));
  74
  75 /* initializes state[N] with a seed */
  76 static void
  77 init_genrand(struct MT *mt, unsigned int s)
  78 {
  79     int j;
  80     mt->state[0] = s & 0xffffffffU;
  81     for (j=1; j<N; j++) {
  82         mt->state[j] = (1812433253U * (mt->state[j-1] ^ (mt->state[j-1] >> 30)) + j);
  83         /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
  84         /* In the previous versions, MSBs of the seed affect   */
  85         /* only MSBs of the array state[].                     */
  86         /* 2002/01/09 modified by Makoto Matsumoto             */
  87         mt->state[j] &= 0xffffffff;  /* for >32 bit machines */
  88     }
  89     mt->left = 1;
  90     mt->next = mt->state + N;
  91 }
  92
  93 /* initialize by an array with array-length */
  94 /* init_key is the array for initializing keys */
  95 /* key_length is its length */
  96 /* slight change for C++, 2004/2/26 */
  97 static void
  98 init_by_array(struct MT *mt, const uint32_t init_key[], int key_length)
  99 {
 100     int i, j, k;
 101     init_genrand(mt, 19650218U);
 102     i=1; j=0;
 103     k = (N>key_length ? N : key_length);
 104     for (; k; k--) {
 105         mt->state[i] = (mt->state[i] ^ ((mt->state[i-1] ^ (mt->state[i-1] >> 30)) * 1664525U))
 106           + init_key[j] + j; /* non linear */
 107         mt->state[i] &= 0xffffffffU; /* for WORDSIZE > 32 machines */
 108         i++; j++;
 109         if (i>=N) { mt->state[0] = mt->state[N-1]; i=1; }
 110         if (j>=key_length) j=0;
 111     }
 112     for (k=N-1; k; k--) {
 113         mt->state[i] = (mt->state[i] ^ ((mt->state[i-1] ^ (mt->state[i-1] >> 30)) * 1566083941U))
 114           - i; /* non linear */
 115         mt->state[i] &= 0xffffffffU; /* for WORDSIZE > 32 machines */
 116         i++;
 117         if (i>=N) { mt->state[0] = mt->state[N-1]; i=1; }
 118     }
 119
 120     mt->state[0] = 0x80000000U; /* MSB is 1; assuring non-zero initial array */
 121 }
 122
 123 static void
 124 next_state(struct MT *mt)
 125 {
 126     uint32_t *p = mt->state;
 127     int j;
 128
 129     mt->left = N;
 130     mt->next = mt->state;
 131
 132     for (j=N-M+1; --j; p++)
 133         *p = p[M] ^ TWIST(p[0], p[1]);
 134
 135     for (j=M; --j; p++)
 136         *p = p[M-N] ^ TWIST(p[0], p[1]);
 137
 138     *p = p[M-N] ^ TWIST(p[0], mt->state[0]);
 139 }
 140
 141 /* generates a random number on [0,0xffffffff]-interval */
 142 static unsigned int
 143 genrand_int32(struct MT *mt)
 144 {
 145     /* mt must be initialized */
 146     unsigned int y;
 147
 148     if (--mt->left <= 0) next_state(mt);
 149     y = *mt->next++;
 150
 151     /* Tempering */
 152     y ^= (y >> 11);
 153     y ^= (y << 7) & 0x9d2c5680;
 154     y ^= (y << 15) & 0xefc60000;
 155     y ^= (y >> 18);
 156
 157     return y;
 158 }