squiggle.c

Self-contained Monte Carlo estimation in C99
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example.c (1292B)


      1 #include "../../../squiggle.h"
      2 #include <stdio.h>
      3 #include <stdlib.h>
      4 
      5 double sample_model(uint64_t* seed){
      6 
      7     double sample_0(uint64_t* seed) { UNUSED(seed); return 0; }
      8     // Using a gcc extension, you can define a function inside another function
      9     double sample_1(uint64_t* seed) { UNUSED(seed); return 1; }
     10     double sample_few(uint64_t* seed) { return sample_to(1, 3, seed); }
     11     double sample_many(uint64_t* seed) { return sample_to(2, 10, seed); }
     12 
     13     double p_a = 0.8;
     14     double p_b = 0.5;
     15     double p_c = p_a * p_b;
     16 
     17     int n_dists = 4;
     18     double weights[] = { 1 - p_c, p_c / 2, p_c / 4, p_c / 4 };
     19     double (*samplers[])(uint64_t*) = { sample_0, sample_1, sample_few, sample_many };
     20     double result = sample_mixture(samplers, weights, n_dists, seed);
     21 
     22     return result;
     23 }
     24 
     25 int main()
     26 {
     27     // set randomness seed
     28     uint64_t* seed = malloc(sizeof(uint64_t));
     29     *seed = 1000; // xorshift can't start with 0
     30 
     31     int n_samples = 1000000;
     32     double* result_many = (double*)malloc((size_t)n_samples * sizeof(double));
     33     for (int i = 0; i < n_samples; i++) {
     34         result_many[i] = sample_model(seed);
     35     }
     36 
     37     printf("result_many: [");
     38     for (int i = 0; i < 100; i++) {
     39         printf("%.2f, ", result_many[i]);
     40     }
     41     printf("]\n");
     42 
     43     free(seed);
     44 }