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/* ------------------------------------------------------------- */
/* File: example_prng.c */
/* ------------------------------------------------------------- */
#ifdef UNURAN_SUPPORTS_PRNG
/* ------------------------------------------------------------- */
/* This example makes use of the PRNG library for generating */
/* uniform random numbers. */
/* (see http://statmath.wu.ac.at/prng/) */
/* To compile this example you must have set */
/* ./configure --with-urng-prng */
/* (Of course the executable has to be linked against the */
/* PRNG library.) */
/* ------------------------------------------------------------- */
/* Include UNURAN header files. */
#include <unuran.h>
#include <unuran_urng_prng.h>
/* ------------------------------------------------------------- */
int main(void)
{
int i; /* loop variable */
double x; /* will hold the random number */
double fparams[2]; /* array for parameters for distribution */
/* Declare the three UNURAN objects. */
UNUR_DISTR *distr; /* distribution object */
UNUR_PAR *par; /* parameter object */
UNUR_GEN *gen; /* generator object */
/* Declare objects for uniform random number generators. */
UNUR_URNG *urng1, *urng2; /* uniform generator objects */
/* PRNG only: */
/* Make a object for uniform random number generator. */
/* For details see http://statmath.wu.ac.at/prng/ */
/* We use the Mersenne Twister. */
urng1 = unur_urng_prng_new("mt19937(1237)");
if (urng1 == NULL) exit (EXIT_FAILURE);
/* Use a predefined standard distribution: */
/* Beta with parameters 2 and 3. */
fparams[0] = 2.;
fparams[1] = 3.;
distr = unur_distr_beta( fparams, 2 );
/* Choose a method: TDR. */
par = unur_tdr_new(distr);
/* Set uniform generator in parameter object */
unur_set_urng( par, urng1 );
/* Create the generator object. */
gen = unur_init(par);
/* Notice that this call has also destroyed the parameter */
/* object `par' as a side effect. */
/* It is important to check if the creation of the generator */
/* object was successful. Otherwise `gen' is the NULL pointer */
/* and would cause a segmentation fault if used for sampling. */
if (gen == NULL) {
fprintf(stderr, "ERROR: cannot create generator object\n");
exit (EXIT_FAILURE);
}
/* It is possible to reuse the distribution object to create */
/* another generator object. If you do not need it any more, */
/* it should be destroyed to free memory. */
unur_distr_free(distr);
/* Now you can use the generator object `gen' to sample from */
/* the distribution. Eg.: */
for (i=0; i<10; i++) {
x = unur_sample_cont(gen);
printf("%f\n",x);
}
/* Now we want to switch to a different uniform random number */
/* generator. */
/* Now we use an ICG (Inversive Congruental Generator). */
urng2 = unur_urng_prng_new("icg(2147483647,1,1,0)");
if (urng2 == NULL) exit (EXIT_FAILURE);
unur_chg_urng( gen, urng2 );
/* ... and sample again. */
for (i=0; i<10; i++) {
x = unur_sample_cont(gen);
printf("%f\n",x);
}
/* When you do not need the generator object any more, you */
/* can destroy it. */
unur_free(gen);
/* We also should destroy the uniform random number generators.*/
unur_urng_free(urng1);
unur_urng_free(urng2);
exit (EXIT_SUCCESS);
} /* end of main() */
/* ------------------------------------------------------------- */
#else
#include <stdio.h>
#include <stdlib.h>
int main(void) {
printf("You must enable the PRNG library to run this example!\n\n");
exit (77); /* exit code for automake check routines */
}
#endif
/* ------------------------------------------------------------- */
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