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/* Interface header file for random number generator functions in libnetpbm */
#ifndef RAND_H_INCLUDED
#define RAND_H_INCLUDED
#include <inttypes.h>
#include "netpbm/pm_c_util.h"
#include "netpbm/mallocvar.h"
/*
Definitions for selecting the random number generator
The default random number generator is Mersenne Twister. Here we
provide a means to revert to the system rand() generator if need be.
Glibc provides generators: rand(), random() and drand48(). Each has
its own associated functions. In the Glibc documentation rand() is
called "ISO", random() is called "BSD" and drand48() is called "SVID".
If your system has the glibc documentation installed "info rand" should
get you to the relevant page. The documentation is available online
from:
https://www.gnu.org/software/libc/manual/html_node/Pseudo_002dRandom-Numbers.html
Pseudo-Random Numbers (The GNU C Library)
Glibc's choice of name is confusing for what it calls "ISO" rand()
was available in early BSD systems.
Functions by these names appear on most Unix systems, but generation
formulas and default initial states are known to differ. On systems
which do not use glibc, what is called rand() may have no relation
with the formula of the ISO C standard. Likewise random() may have
no relation with the BSD formula.
*/
enum PmRandEngine {PM_RAND_SYS_RAND, /* rand() */
PM_RAND_SYS_RANDOM, /* random() */
PM_RAND_SYS_DRAND48, /* drand48() reserved */
PM_RAND_MERSENNETWISTER /* default */};
#ifndef PM_RANDOM_NUMBER_GENERATOR
#define PM_RANDOM_NUMBER_GENERATOR PM_RAND_MERSENNETWISTER
#endif
/* Structure to hold random number generator profile and internal state */
struct pm_randSt;
struct pm_rand_vtable {
void
(*init)(struct pm_randSt * const randStP);
void
(*srand)(struct pm_randSt * const randStP,
unsigned int const seed);
unsigned long int
(*rand)(struct pm_randSt * const randStP);
};
extern struct pm_rand_vtable const pm_randsysrand_vtable;
extern struct pm_rand_vtable const pm_randsysrandom_vtable;
extern struct pm_rand_vtable const pm_randmersenne_vtable;
struct pm_randSt {
struct pm_rand_vtable vtable;
void * stateP; /* Internal state */
unsigned int max;
unsigned int seed;
bool gaussCacheValid;
double gaussCache;
};
/* Function declarations */
extern void
pm_randinit(struct pm_randSt * const randStP);
extern void
pm_randterm(struct pm_randSt * const randStP);
extern void
pm_srand(struct pm_randSt * const randStP,
unsigned int const seed);
extern void
pm_srand2(struct pm_randSt * const randStP,
bool const withSeed,
unsigned int const seedVal);
extern unsigned long int
pm_rand(struct pm_randSt * const randStP);
extern double
pm_drand(struct pm_randSt * const randStP);
extern void
pm_gaussrand2(struct pm_randSt * const randStP,
double * const r1P,
double * const r2P);
extern double
pm_gaussrand(struct pm_randSt * const randStP);
extern uint32_t
pm_rand32(struct pm_randSt * const randStP);
#endif
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