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/**
* @file tinymt32.c
*
* @brief Tiny Mersenne Twister only 127 bit internal state
*
* @author Mutsuo Saito (Hiroshima University)
* @author Makoto Matsumoto (The University of Tokyo)
*
* Copyright (C) 2011 Mutsuo Saito, Makoto Matsumoto,
* Hiroshima University and The University of Tokyo.
* All rights reserved.
*
* The 3-clause BSD License is applied to this software, see
* LICENSE.txt
*/
#include "tinymt32.h"
#define MIN_LOOP 8
#define PRE_LOOP 8
/**
* This function represents a function used in the initialization
* by init_by_array
* @param x 32-bit integer
* @return 32-bit integer
*/
static uint32_t ini_func1(uint32_t x)
{
return (x ^ (x >> 27)) * UINT32_C(1664525);
}
/**
* This function represents a function used in the initialization
* by init_by_array
* @param x 32-bit integer
* @return 32-bit integer
*/
static uint32_t ini_func2(uint32_t x)
{
return (x ^ (x >> 27)) * UINT32_C(1566083941);
}
/**
* This function certificate the period of 2^127-1.
* @param random tinymt state vector.
*/
static void period_certification(tinymt32_t *random)
{
if ((random->status[0] & TINYMT32_MASK) == 0 &&
random->status[1] == 0 &&
random->status[2] == 0 &&
random->status[3] == 0) {
random->status[0] = 'T';
random->status[1] = 'I';
random->status[2] = 'N';
random->status[3] = 'Y';
}
}
/**
* This function initializes the internal state array with a 32-bit
* unsigned integer seed.
* @param random tinymt state vector.
* @param seed a 32-bit unsigned integer used as a seed.
*/
void tinymt32_init(tinymt32_t *random, uint32_t seed)
{
random->status[0] = seed;
random->status[1] = random->mat1;
random->status[2] = random->mat2;
random->status[3] = random->tmat;
for (int i = 1; i < MIN_LOOP; i++) {
random->status[i & 3] ^= i + UINT32_C(1812433253)
* (random->status[(i - 1) & 3]
^ (random->status[(i - 1) & 3] >> 30));
}
period_certification(random);
for (int i = 0; i < PRE_LOOP; i++) {
tinymt32_next_state(random);
}
}
/**
* This function initializes the internal state array,
* with an array of 32-bit unsigned integers used as seeds
* @param random tinymt state vector.
* @param init_key the array of 32-bit integers, used as a seed.
* @param key_length the length of init_key.
*/
void tinymt32_init_by_array(tinymt32_t *random, uint32_t init_key[],
int key_length)
{
const int lag = 1;
const int mid = 1;
const int size = 4;
int i, j;
int count;
uint32_t r;
uint32_t *st = &random->status[0];
st[0] = 0;
st[1] = random->mat1;
st[2] = random->mat2;
st[3] = random->tmat;
if (key_length + 1 > MIN_LOOP) {
count = key_length + 1;
}
else {
count = MIN_LOOP;
}
r = ini_func1(st[0] ^ st[mid % size]
^ st[(size - 1) % size]);
st[mid % size] += r;
r += key_length;
st[(mid + lag) % size] += r;
st[0] = r;
count--;
for (i = 1, j = 0; (j < count) && (j < key_length); j++) {
r = ini_func1(st[i % size]
^ st[(i + mid) % size]
^ st[(i + size - 1) % size]);
st[(i + mid) % size] += r;
r += init_key[j] + i;
st[(i + mid + lag) % size] += r;
st[i % size] = r;
i = (i + 1) % size;
}
for (; j < count; j++) {
r = ini_func1(st[i % size]
^ st[(i + mid) % size]
^ st[(i + size - 1) % size]);
st[(i + mid) % size] += r;
r += i;
st[(i + mid + lag) % size] += r;
st[i % size] = r;
i = (i + 1) % size;
}
for (j = 0; j < size; j++) {
r = ini_func2(st[i % size]
+ st[(i + mid) % size]
+ st[(i + size - 1) % size]);
st[(i + mid) % size] ^= r;
r -= i;
st[(i + mid + lag) % size] ^= r;
st[i % size] = r;
i = (i + 1) % size;
}
period_certification(random);
for (i = 0; i < PRE_LOOP; i++) {
tinymt32_next_state(random);
}
}
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