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/* Random kit 1.3 */
/*
* Copyright (c) 2003-2005, Jean-Sebastien Roy (js@jeannot.org)
*
* The rk_random and rk_seed functions algorithms and the original design of
* the Mersenne Twister RNG:
*
* 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.
*
* Original algorithm for the implementation of rk_interval function from
* Richard J. Wagner's implementation of the Mersenne Twister RNG, optimised by
* Magnus Jonsson.
*
* Constants used in the rk_double implementation by Isaku Wada.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <math.h>
#include <neatogen/randomkit.h>
void
rk_seed(unsigned long seed, rk_state *state)
{
int pos;
seed &= 0xffffffffUL;
/* Knuth's PRNG as used in the Mersenne Twister reference implementation */
for (pos = 0; pos < RK_STATE_LEN; pos++) {
state->key[pos] = seed;
seed = (1812433253UL * (seed ^ (seed >> 30)) + pos + 1) & 0xffffffffUL;
}
state->pos = RK_STATE_LEN;
}
/* Magic Mersenne Twister constants */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL
#define UPPER_MASK 0x80000000UL
#define LOWER_MASK 0x7fffffffUL
/* Slightly optimised reference implementation of the Mersenne Twister */
unsigned long
rk_random(rk_state *state)
{
unsigned long y;
if (state->pos == RK_STATE_LEN) {
int i;
for (i = 0; i < N - M; i++) {
y = (state->key[i] & UPPER_MASK) | (state->key[i+1] & LOWER_MASK);
state->key[i] = state->key[i+M] ^ (y>>1) ^ ((y & 1) * MATRIX_A);
}
for (; i < N - 1; i++) {
y = (state->key[i] & UPPER_MASK) | (state->key[i+1] & LOWER_MASK);
state->key[i] = state->key[i+(M-N)] ^ (y>>1) ^ ((y & 1) * MATRIX_A);
}
y = (state->key[N - 1] & UPPER_MASK) | (state->key[0] & LOWER_MASK);
state->key[N - 1] = state->key[M - 1] ^ (y >> 1) ^ ((y & 1) * MATRIX_A);
state->pos = 0;
}
y = state->key[state->pos++];
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return y;
}
/// returns a random unsigned long between 0 and `ULONG_MAX` inclusive
static unsigned long rk_ulong(rk_state *state) {
#if ULONG_MAX <= 0xffffffffUL
return rk_random(state);
#else
return (rk_random(state) << 32) | (rk_random(state));
#endif
}
unsigned long
rk_interval(unsigned long max, rk_state *state)
{
unsigned long mask = max, value;
if (max == 0) {
return 0;
}
/* Smallest bit mask >= max */
mask |= mask >> 1;
mask |= mask >> 2;
mask |= mask >> 4;
mask |= mask >> 8;
mask |= mask >> 16;
#if ULONG_MAX > 0xffffffffUL
mask |= mask >> 32;
#endif
/* Search a random value in [0..mask] <= max */
#if ULONG_MAX > 0xffffffffUL
if (max <= 0xffffffffUL) {
while ((value = (rk_random(state) & mask)) > max);
}
else {
while ((value = (rk_ulong(state) & mask)) > max);
}
#else
while ((value = (rk_ulong(state) & mask)) > max);
#endif
return value;
}
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