ref: f6d97317c22b5d2e703844728a3f41b6bc3a74a4
dir: /modules/randmt.c/
/*
A C-program for MT19937, with initialisation improved 2002/1/26.
Coded by Takuji Nishimura and Makoto Matsumoto.
Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. The names of its contributors may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
Any feedback is very welcome.
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/
#include "soundpipe.h"
#define N (624)
#define M (397)
#define MATRIX_A 0x9908B0DFU /* constant vector a */
#define UPPER_MASK 0x80000000U /* most significant w-r bits */
#define LOWER_MASK 0x7FFFFFFFU /* least significant r bits */
static void MT_update_state(uint32_t *mt)
{
/* mag01[x] = x * MATRIX_A for x=0,1 */
const uint32_t mag01[2] = { (uint32_t) 0, (uint32_t) MATRIX_A };
int i;
uint32_t y;
for (i = 0; i < (N - M); i++) {
y = (mt[i] & UPPER_MASK) | (mt[i + 1] & LOWER_MASK);
mt[i] = mt[i + M] ^ (y >> 1) ^ mag01[y & (uint32_t) 1];
}
for ( ; i < (N - 1); i++) {
y = (mt[i] & UPPER_MASK) | (mt[i + 1] & LOWER_MASK);
mt[i] = mt[i + (M - N)] ^ (y >> 1) ^ mag01[y & (uint32_t) 1];
}
y = (mt[N - 1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
mt[N - 1] = mt[M - 1] ^ (y >> 1) ^ mag01[y & (uint32_t) 1];
}
/* generates a random number on [0,0xffffffff]-interval */
uint32_t sp_randmt_compute(sp_randmt *p)
{
int i = p->mti;
uint32_t y;
if (i >= N) { /* generate N words at one time */
MT_update_state(&(p->mt[0]));
i = 0;
}
y = p->mt[i];
p->mti = i + 1;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & (uint32_t) 0x9D2C5680U;
y ^= (y << 15) & (uint32_t) 0xEFC60000U;
y ^= (y >> 18);
return y;
}
void sp_randmt_seed(sp_randmt *p,
const uint32_t *initKey, uint32_t keyLength)
{
int i, j, k;
uint32_t x;
/* if array is NULL, use length parameter as simple 32 bit seed */
x = (initKey == NULL ? keyLength : (uint32_t) 19650218);
p->mt[0] = x;
for (i = 1; i < N; i++) {
/* 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 */
x = ((uint32_t) 1812433253 * (x ^ (x >> 30)) + (uint32_t) i);
p->mt[i] = x;
}
p->mti = N;
if (initKey == NULL)
return;
i = 0; j = 0;
k = (N > (int) keyLength ? N : (int) keyLength);
for ( ; k; k--) {
x = p->mt[i++];
p->mt[i] = (p->mt[i] ^ ((x ^ (x >> 30)) * (uint32_t) 1664525))
+ initKey[j] + (uint32_t) j; /* non linear */
if (i == (N - 1)) {
p->mt[0] = p->mt[N - 1];
i = 0;
}
if (++j >= (int) keyLength)
j = 0;
}
for (k = (N - 1); k; k--) {
x = p->mt[i++];
p->mt[i] = (p->mt[i] ^ ((x ^ (x >> 30)) * (uint32_t) 1566083941))
- (uint32_t) i; /* non linear */
if (i == (N - 1)) {
p->mt[0] = p->mt[N - 1];
i = 0;
}
}
/* MSB is 1; assuring non-zero initial array */
p->mt[0] = (uint32_t) 0x80000000U;
}