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/* Copyright (c) 2001, Stanford University
* All rights reserved
*
* See the file LICENSE.txt for information on redistributing this software.
*/
#include "cr_rand.h"
#ifdef WINDOWS
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#else
#include <sys/time.h>
#endif
/* Period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */
/* Tempering parameters */
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y) (y >> 11)
#define TEMPERING_SHIFT_S(y) (y << 7)
#define TEMPERING_SHIFT_T(y) (y << 15)
#define TEMPERING_SHIFT_L(y) (y >> 18)
static unsigned long mt[N]; /* the array for the state vector */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */
void crRandSeed(unsigned long seed)
{
/* setting initial seeds to mt[N] using the generator Line 25 of Table 1
in [KNUTH 1981, The Art of Computer Programming Vol. 2 (2nd Ed.),
pp102
*/
if (seed == 0)
seed = 4357; /* pick default seed if seed=0 (Guy Zadickario) */
mt[0]= seed & 0xffffffff;
for (mti=1; mti<N; mti++)
mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
}
/*
* Seed the generator based on time of day or a system counter.
*/
void crRandAutoSeed(void)
{
#if defined(WINDOWS)
LARGE_INTEGER counter;
QueryPerformanceCounter( &counter );
crRandSeed((unsigned long) counter.QuadPart);
#else
struct timeval timeofday;
gettimeofday( &timeofday, 0 );
crRandSeed((unsigned long) timeofday.tv_usec);
#endif
}
static double genrand( void )
{
unsigned long y;
static unsigned long mag01[2]={0x0, MATRIX_A};
/* mag01[x] = x * MATRIX_A for x=0,1 */
if (mti >= N) { /* generate N words at one time */
int kk;
if (mti == N+1) /* if sgenrand() has not been called, */
crRandSeed(4357); /* a default initial seed is used */
for (kk=0;kk<N-M;kk++) {
y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
}
for (;kk<N-1;kk++) {
y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
}
y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
mti = 0;
}
y = mt[mti++];
y ^= TEMPERING_SHIFT_U(y);
y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
y ^= TEMPERING_SHIFT_L(y);
return ( (double)y / (unsigned long)0xffffffff ); /* reals */
/* return y; */ /* for integer generation */
}
float crRandFloat(float min, float max)
{
double t = genrand();
return (float) (t*min + (1-t)*max);
}
/* return a random integer in [min, max] (inclusive). */
int crRandInt(int min, int max)
{
double t = genrand();
return min + (int) (t * (max - min + 1));
}
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