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/*
* libmowgli: A collection of useful routines for programming.
* random.c: Portable mersinne-twister based psuedo-random number generator.
*
* Copyright (c) 2007 William Pitcock <nenolod -at- sacredspiral.co.uk>
* Algorithm copyright (c) 1999-2007 Takuji Nishimura and Makoto Matsumoto
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice is present in all copies.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
#include "mowgli.h"
/* period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL /* constant vector a */
#define UPPER_MASK 0x80000000UL /* most significant w-r bits */
#define LOWER_MASK 0x7fffffffUL /* least significant r bits */
/* mowgli_random_t contains state data which is private */
struct mowgli_random_
{
mowgli_object_t object;
unsigned int mt[N];
size_t mti;
};
static mowgli_object_class_t klass;
/* initialization */
void mowgli_random_bootstrap(void)
{
mowgli_object_class_init(&klass, "mowgli_random_t", NULL, FALSE);
}
/* construction and destruction. */
mowgli_random_t *mowgli_random_create(void)
{
return mowgli_random_create_with_seed(time(NULL));
}
mowgli_random_t *mowgli_random_create_with_seed(unsigned int seed)
{
mowgli_random_t *out = mowgli_alloc(sizeof(mowgli_random_t));
mowgli_object_init(mowgli_object(out), NULL, &klass, NULL);
mowgli_random_reseed(out, seed);
return out;
}
/* reset seed */
void mowgli_random_reseed(mowgli_random_t *self, unsigned int seed)
{
return_if_fail(self != NULL);
self->mt[0] = seed & 0xffffffffUL;
for (self->mti = 1; self->mti < N; self->mti++)
{
self->mt[self->mti] = (1812433253UL * (self->mt[self->mti - 1] ^ (self->mt[self->mti - 1] >> 30)) + self->mti);
self->mt[self->mti] &= 0xffffffffUL;
}
}
/* number retrieval */
unsigned int mowgli_random_int(mowgli_random_t *self)
{
unsigned int y;
static unsigned int mag01[2] = { 0x0UL, MATRIX_A };
return_val_if_fail(self != NULL, 0);
if (self->mti >= N)
{
int t;
for (t = 0; t < N - M; t++)
{
y = (self->mt[t] & UPPER_MASK) | (self->mt[t + 1] & LOWER_MASK);
self->mt[t] = self->mt[t + M] ^ (y >> 1) ^ mag01[y & 0x1U];
}
for (; t < N - 1; t++)
{
y = (self->mt[t] & UPPER_MASK) | (self->mt[t + 1] & LOWER_MASK);
self->mt[t] = self->mt[t + (M - N)] ^ (y >> 1) ^ mag01[y & 0x1U];
}
y = (self->mt[N - 1] & UPPER_MASK) | (self->mt[0] & LOWER_MASK);
self->mt[N - 1] = self->mt[M - 1] ^ (y >> 1) ^ mag01[y & 0x1U];
self->mti = 0;
}
y = self->mt[self->mti++];
/* tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680U;
y ^= (y << 15) & 0xefc60000U;
y ^= (y >> 18);
return y;
}
int mowgli_random_int_ranged(mowgli_random_t *self, int begin, int end)
{
unsigned int dist = end - begin;
unsigned int max, ret;
if (dist <= 0x80000000U)
{
unsigned int remain = (0x80000000U % dist) * 2;
if (remain >= dist)
remain -= dist;
max = 0xFFFFFFFFU - remain;
} else
max = dist - 1;
do
{
ret = mowgli_random_int(self);
} while (ret > max);
ret %= dist;
return begin + ret;
}
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