/* ------------------------------------------------------------- */ /* File: example_prng_str.c */ /* ------------------------------------------------------------- */ /* String API. */ /* ------------------------------------------------------------- */ #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 */ /* Declare UNURAN generator object. */ UNUR_GEN *gen; /* generator object */ /* Declare objects for uniform random number generators. */ UNUR_URNG *urng1, *urng2; /* uniform generator objects */ /* Create the generator object. */ /* Use a predefined standard distribution: */ /* Beta with parameters 2 and 3. */ /* Choose a method: TDR. */ /* Use the Mersenne Twister for unifrom random number */ /* generator (requires PRNG library). */ gen = unur_str2gen("beta(2,3) & method=tdr & urng = mt19937(1237)"); /* 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); } /* 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); /* Change uniform random number generator. */ /* Notice however that we should save the pointer to uniform */ /* random number generator in the generator object. */ urng1 = 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 /* ------------------------------------------------------------- */