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/* ------------------------------------------------------------- */
/* File: example_reinit.c */
/* ------------------------------------------------------------- */
/* Include UNURAN header file. */
#include <unuran.h>
/* ------------------------------------------------------------- */
/* In this example we show how the parameters of the underlying */
/* distribution can be changed for an existing generator object. */
/* We use the GIG distribution with method CSTD. */
/* ------------------------------------------------------------- */
int main(void)
{
int i; /* loop variable */
double x; /* will hold the random number */
/* Parameters of distribution. */
double dparam[3] = {0.5, 1., 5.};
/* Declare the three UNURAN objects. */
UNUR_DISTR *distr; /* distribution object */
UNUR_PAR *par; /* parameter object */
UNUR_GEN *gen; /* generator object */
/* Create initial GIG distribution object */
distr = unur_distr_gig(dparam, 3);
/* Choose a method: CSTD. */
par = unur_cstd_new(distr);
/* Create the generator object. */
gen = unur_init(par);
/* 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);
}
/* It is possible for method CSTD to change the parameters of */
/* underlying distribution. However, we have to extract to */
/* pointer to the distribution. Be carefull with this pointer! */
distr = unur_get_distr(gen);
/* Change the parameter(s). */
dparam[2] = 0.001;
unur_distr_cont_set_pdfparams(distr,dparam,3);
/* Do not forget to reinitialize the generator object. */
/* Check the return code. */
/* (and try to find a better error handling) */
if (unur_reinit(gen) != UNUR_SUCCESS) {
fprintf(stderr, "ERROR: cannot reinitialize generator object\n");
exit (EXIT_FAILURE);
}
/* Draw a new sample. */
for (i=0; i<10; i++) {
x = unur_sample_cont(gen);
printf("%f\n",x);
}
/* Changing parameters can be repeated. */
dparam[2] = 1000;
unur_distr_cont_set_pdfparams(distr,dparam,3);
if (unur_reinit(gen) != UNUR_SUCCESS) {
fprintf(stderr, "ERROR: cannot reinitialize generator object\n");
exit (EXIT_FAILURE);
}
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);
exit (EXIT_SUCCESS);
} /* end of main() */
/* ------------------------------------------------------------- */
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