122 lines
3.4 KiB
C
122 lines
3.4 KiB
C
/**
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* @file tinymt32.c
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*
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* @brief Tiny Mersenne Twister only 127 bit internal state
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*
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* @author Mutsuo Saito (Hiroshima University)
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* @author Makoto Matsumoto (The University of Tokyo)
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*
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* Copyright (C) 2011 Mutsuo Saito, Makoto Matsumoto,
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* Hiroshima University and The University of Tokyo.
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* All rights reserved.
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*
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* The 3-clause BSD License is applied to this software, see
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* LICENSE.txt
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*/
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/* Note: this is a stripped-down version of TinyMT that only includes the
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32-bit integer generator. For the full version, please see
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<https://github.com/MersenneTwister-Lab/TinyMT>. */
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#include "tinymt32.h"
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#define TINYMT32_SH0 1
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#define TINYMT32_SH1 10
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#define TINYMT32_SH8 8
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#define TINYMT32_MASK 0x7fffffff
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/**
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* This function changes internal state of tinymt32.
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* Users should not call this function directly.
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* @param random tinymt internal status
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*/
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static void tinymt32_next_state(tinymt32_t * random) {
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uint32_t x;
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uint32_t y;
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y = random->status[3];
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x = (random->status[0] & TINYMT32_MASK)
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^ random->status[1]
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^ random->status[2];
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x ^= (x << TINYMT32_SH0);
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y ^= (y >> TINYMT32_SH0) ^ x;
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random->status[0] = random->status[1];
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random->status[1] = random->status[2];
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random->status[2] = x ^ (y << TINYMT32_SH1);
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random->status[3] = y;
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random->status[1] ^= -((int32_t)(y & 1)) & random->mat1;
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random->status[2] ^= -((int32_t)(y & 1)) & random->mat2;
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}
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/**
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* This function outputs 32-bit unsigned integer from internal state.
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* Users should not call this function directly.
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* @param random tinymt internal status
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* @return 32-bit unsigned pseudorandom number
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*/
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static uint32_t tinymt32_temper(tinymt32_t * random) {
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uint32_t t0, t1;
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t0 = random->status[3];
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#if defined(LINEARITY_CHECK)
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t1 = random->status[0]
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^ (random->status[2] >> TINYMT32_SH8);
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#else
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t1 = random->status[0]
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+ (random->status[2] >> TINYMT32_SH8);
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#endif
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t0 ^= t1;
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t0 ^= -((int32_t)(t1 & 1)) & random->tmat;
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return t0;
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}
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/**
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* This function outputs 32-bit unsigned integer from internal state.
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* @param random tinymt internal status
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* @return 32-bit unsigned integer r (0 <= r < 2^32)
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*/
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uint32_t tinymt32_generate_uint32(tinymt32_t * random) {
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tinymt32_next_state(random);
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return tinymt32_temper(random);
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}
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#define MIN_LOOP 8
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#define PRE_LOOP 8
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/**
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* This function certificate the period of 2^127-1.
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* @param random tinymt state vector.
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*/
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static void period_certification(tinymt32_t * random) {
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if ((random->status[0] & TINYMT32_MASK) == 0 &&
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random->status[1] == 0 &&
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random->status[2] == 0 &&
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random->status[3] == 0) {
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random->status[0] = 'T';
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random->status[1] = 'I';
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random->status[2] = 'N';
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random->status[3] = 'Y';
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}
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}
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/**
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* This function initializes the internal state array with a 32-bit
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* unsigned integer seed.
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* @param random tinymt state vector.
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* @param seed a 32-bit unsigned integer used as a seed.
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*/
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void tinymt32_init(tinymt32_t * random, uint32_t seed) {
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random->status[0] = seed;
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random->status[1] = random->mat1;
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random->status[2] = random->mat2;
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random->status[3] = random->tmat;
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for (int i = 1; i < MIN_LOOP; i++) {
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random->status[i & 3] ^= i + UINT32_C(1812433253)
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* (random->status[(i - 1) & 3]
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^ (random->status[(i - 1) & 3] >> 30));
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}
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period_certification(random);
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for (int i = 0; i < PRE_LOOP; i++) {
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tinymt32_next_state(random);
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}
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}
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