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/* Integer and floating point random number generator routines */
/*
* Copyright 2000 Graeme W. Gill
* All rights reserved.
*
* This material is licenced under the GNU AFFERO GENERAL PUBLIC LICENSE Version 3 :-
* see the License.txt file for licencing details.
*/
#include "numsup.h"
#include "rand.h"
/* 32 bit pseudo random sequencer based on XOR feedback */
/* generates number between 1 and 4294967295 */
#define PSRAND32(S) (((S) & 0x80000000) ? (((S) << 1) ^ 0xa398655d) : ((S) << 1))
/* 32 bit linear congruent generator */
/* generates number between 0 and 4294967295 */
/* (From Knuth & H.W.Lewis) */
#define PSRAND32L(S) ((S) * 1664525L + 1013904223L)
/* - - - - - - - - - - - - - - - */
/* Global state random generator */
static rand_state g_rand = { 0 }; /* Use default seed for global state generator */
/* Return a 32 bit number between 0 and 4294967295 */
/* Use Knuth shuffle to improve PSRAND32 sequence */
unsigned int
rand32( /* Return 32 bit random number */
unsigned int seed /* Optional seed. Non-zero re-initialized with that seed */
) {
return rand32_th(NULL, seed);
}
/* return a random number between 0.0 and 1.0 */
/* based on rand32 */
double ranno(void) {
return rand32_th(NULL, 0) / 4294967295.0;
}
/* Return a uniform random double in the range min to max */
double
d_rand(double min, double max) {
return d_rand_th(NULL, min, max);
}
/* Return a squared distribution random double in the range min to max */
double
d2_rand(double min, double max) {
return d2_rand_th(NULL, min, max);
}
/* Return a random integer in the range min to max inclusive */
int
i_rand(int min, int max) {
return i_rand_th(NULL, min, max);
}
/* Return a random floating point number with a gausian/normal */
/* distribution, centered about 0.0, with standard deviation 1.0 */
/* This uses the Box-Muller transformation */
double norm_rand(void) {
return norm_rand_th(NULL);
}
/* - - - - - - - - - - - - - - - */
/* Explicit state random generator */
/* Init rand_state to default */
void rand_init(rand_state *p) {
if (p == NULL)
p = &g_rand;
p->pvs_inited = 0;
p->ran = 0;
}
/* Return a 32 bit number between 0 and 4294967295 */
/* Use Knuth shuffle to improve PSRAND32 sequence */
unsigned int
rand32_th(rand_state *p,
unsigned int seed /* Optional seed. Non-zero re-initialized with that seed */
) {
int i;
if (p == NULL)
p = &g_rand;
if (seed != 0) {
//printf("~1 rand 0x%x seed 0x%x\n",p,seed);
p->pvs_inited = 0;
p->ran = seed;
}
/* Init random storage locations */
if (p->pvs_inited == 0) {
if (p->ran == 0)
p->ran = RAND_SEED;
for (i = 0; i < RAND_TSIZE; i++)
p->pvs[i] = p->ran = PSRAND32(p->ran);
p->last = p->ran;
p->pvs_inited = 1;
}
i = p->last % RAND_TSIZE; /* New location */
p->last = p->pvs[i]; /* Value generated */
p->pvs[i] = p->ran = PSRAND32(p->ran); /* New value */
//printf("~1 rand 0x%x ret 0x%x\n",p,p->last-1);
return p->last-1;
}
/* return a random number between 0.0 and 1.0 */
/* based on rand32 */
double ranno_th(rand_state *p) {
return rand32_th(p, 0) / 4294967295.0;
}
/* Return a uniform random double in the range min to max */
double
d_rand_th(rand_state *p, double min, double max) {
return min + (max - min) * ranno_th(p);
}
/* Return a squared distribution random double in the range min to max */
double
d2_rand_th(rand_state *p, double min, double max) {
double val = ranno_th(p);
return min + (max - min) * val * val;
}
/* Return a random integer in the range min to max inclusive */
int
i_rand_th(rand_state *p, int min, int max) {
return min + (int)floor(0.5 + ((double)(max - min)) * ranno_th(p));
}
/* Return a random floating point number with a gausian/normal */
/* distribution, centered about 0.0, with standard deviation 1.0 */
/* This uses the Box-Muller transformation */
double norm_rand_th(rand_state *p) {
if (p == NULL)
p = &g_rand;
if (p->r2 == 0) {
double v1, v2, t1, t2, r1;
do {
v1 = d_rand_th(p, -1.0, 1.0);
v2 = d_rand_th(p, -1.0, 1.0);
t1 = v1 * v1 + v2 * v2;
} while (t1 == 0.0 || t1 >= 1.0);
t2 = sqrt(-2.0 * log(t1)/t1);
p->nr2 = v2 * t2; /* One for next time */
p->r2 = 1;
r1 = v1 * t2;
return r1;
} else {
p->r2 = 0;
return p->nr2;
}
}
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