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psyclpc/src/random.c

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/*---------------------------------------------------------------------------
* Gamedriver: Random Generator 'Mersenne Twister'
*
* A C-program for MT19937, with initialization improved 2002/2/10.
* Coded by Takuji Nishimura and Makoto Matsumoto.
* This is a faster version by taking Shawn Cokus's optimization,
* Matthe Bellew's simplification, Isaku Wada's real version.
*
* Before using, initialize the state by using init_genrand(seed)
* or init_by_array(init_key, key_length).
*
* 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.keio.ac.jp/matumoto/emt.html
* email: matumoto@math.keio.ac.jp
*---------------------------------------------------------------------------
*/
#include "driver.h"
#include "random.h"
/* Period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL /* constant vector a */
#define UMASK 0x80000000UL /* most significant w-r bits */
#define LMASK 0x7fffffffUL /* least significant r bits */
#define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
#define TWIST(u,v) ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL))
static unsigned long state[N]; /* the array for the state vector */
static int left = 1;
static int initf = 0;
static unsigned long *next;
/* initializes state[N] with a seed */
void init_genrand(unsigned long s)
{
int j;
state[0]= s & 0xffffffffUL;
for (j=1; j<N; j++) {
state[j] = (1812433253UL * (state[j-1] ^ (state[j-1] >> 30)) + j);
/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
/* In the previous versions, MSBs of the seed affect */
/* only MSBs of the array state[]. */
/* 2002/01/09 modified by Makoto Matsumoto */
state[j] &= 0xffffffffUL; /* for >32 bit machines */
}
left = 1; initf = 1;
}
/* initialize by an array with array-length */
/* init_key is the array for initializing keys */
/* key_length is its length */
/* slight change for C++, 2004/2/26 */
void init_by_array(unsigned long init_key[], int key_length)
{
int i, j, k;
init_genrand(19650218UL);
i=1; j=0;
k = (N>key_length ? N : key_length);
for (; k; k--) {
state[i] = (state[i] ^ ((state[i-1] ^ (state[i-1] >> 30)) * 1664525UL))
+ init_key[j] + j; /* non linear */
state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
i++; j++;
if (i>=N) { state[0] = state[N-1]; i=1; }
if (j>=key_length) j=0;
}
for (k=N-1; k; k--) {
state[i] = (state[i] ^ ((state[i-1] ^ (state[i-1] >> 30)) * 1566083941UL))
- i; /* non linear */
state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
i++;
if (i>=N) { state[0] = state[N-1]; i=1; }
}
state[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
left = 1; initf = 1;
}
static void next_state(void)
{
unsigned long *p=state;
int j;
/* if init_genrand() has not been called, */
/* a default initial seed is used */
if (initf==0) init_genrand(5489UL);
left = N;
next = state;
for (j=N-M+1; --j; p++)
*p = p[M] ^ TWIST(p[0], p[1]);
for (j=M; --j; p++)
*p = p[M-N] ^ TWIST(p[0], p[1]);
*p = p[M-N] ^ TWIST(p[0], state[0]);
}
/* generates a random number on [0,0xffffffff]-interval */
unsigned long genrand_int32(void)
{
unsigned long y;
if (--left == 0) next_state();
y = *next++;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return y;
}
#if 0
/** LDMud doesn't use the following functions - yet. **/
/* generates a random number on [0,0x7fffffff]-interval */
long genrand_int31(void)
{
unsigned long y;
if (--left == 0) next_state();
y = *next++;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return (long)(y>>1);
}
/* generates a random number on [0,1]-real-interval */
double genrand_real1(void)
{
unsigned long y;
if (--left == 0) next_state();
y = *next++;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return (double)y * (1.0/4294967295.0);
/* divided by 2^32-1 */
}
/* generates a random number on [0,1)-real-interval */
double genrand_real2(void)
{
unsigned long y;
if (--left == 0) next_state();
y = *next++;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return (double)y * (1.0/4294967296.0);
/* divided by 2^32 */
}
/* generates a random number on (0,1)-real-interval */
double genrand_real3(void)
{
unsigned long y;
if (--left == 0) next_state();
y = *next++;
/* Tempering */
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return ((double)y + 0.5) * (1.0/4294967296.0);
/* divided by 2^32 */
}
/* generates a random number on [0,1) with 53-bit resolution*/
double genrand_res53(void)
{
unsigned long a=genrand_int32()>>5, b=genrand_int32()>>6;
return(a*67108864.0+b)*(1.0/9007199254740992.0);
}
/* These real versions are due to Isaku Wada, 2002/01/09 added */
#endif
/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/
/* Driver interface functions */
/*-------------------------------------------------------------------------*/
void
seed_random (uint32 seed)
/* Initialize the generator */
{
unsigned long init[4];
init[0] = seed & 0xFFF;
init[1] = (seed >>= 8) & 0xFFF;
init[2] = (seed >>= 8) & 0xFFF;
init[3] = (seed >>= 8) & 0xFFF;
init_by_array(init, 4);
} /* seed_random() */
/*-------------------------------------------------------------------------*/
uint32
random_number (uint32 n)
/* Return a random number in the range 0..n-1.
*
* The MT FAQ suggests:
* If the application is not sensitive to the rounding off error, then please
* multiply N to [0,1)-real uniform random numbers and take the integer part
* (this is sufficient for most applications).
*
*/
{
return genrand_int32() * (1.0/4294967296.0) * n;
/*
* Since most compilers compute the constant when it is compiled, so this
* code runs with the same speed with the standard C codes, and portability
* and readability are better.
*/
} /* random_number() */
/***************************************************************************/
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