time-to-botec

samples-one-thread.c (4420B)

---

 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 
 const float PI = 3.14159265358979323846;
 
 #define N 1000000
 
 //Array helpers
 
 void array_print(float* array, int length)
 {
     for (int i = 0; i < length; i++) {
         printf("item[%d] = %f\n", i, array[i]);
     }
     printf("\n");
 }
 
 void array_fill(float* array, int length, float item)
 {
     int i;
     {
         for (i = 0; i < length; i++) {
             array[i] = item;
         }
     }
 }
 
 float array_sum(float* array, int length)
 {
     float output = 0.0;
     for (int i = 0; i < length; i++) {
         output += array[i];
     }
     return output;
 }
 
 void array_cumsum(float* array_to_sum, float* array_cumsummed, int length)
 {
     array_cumsummed[0] = array_to_sum[0];
     for (int i = 1; i < length; i++) {
         array_cumsummed[i] = array_cumsummed[i - 1] + array_to_sum[i];
     }
 }
 
 float rand_float(float to)
 {
     return ((float)rand() / (float)RAND_MAX) * to;
 }
 
 float ur_normal()
 {
     float u1 = rand_float(1.0);
     float u2 = rand_float(1.0);
     float z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
     return z;
 }
 
 inline float random_uniform(float from, float to)
 {
     return ((float)rand() / (float)RAND_MAX) * (to - from) + from;
 }
 
 inline float random_normal(float mean, float sigma)
 {
     return (mean + sigma * ur_normal());
 }
 
 inline float random_lognormal(float logmean, float logsigma)
 {
     return expf(random_normal(logmean, logsigma));
 }
 
 inline float random_to(float low, float high)
 {
     const float NORMAL95CONFIDENCE = 1.6448536269514722;
     float loglow = logf(low);
     float loghigh = logf(high);
     float logmean = (loglow + loghigh) / 2;
     float logsigma = (loghigh - loglow) / (2.0 * NORMAL95CONFIDENCE);
     return random_lognormal(logmean, logsigma);
 }
 
 void array_random_to(float* array, int length, float low, float high)
 {
     int i;
     #pragma omp private(i)
     {
         #pragma omp for
         for (i = 0; i < length; i++) {
             array[i] = random_to(low, high);
         }
     }
 }
 
 void mixture(float (*samplers[])(void), float* weights, int n_dists, float* results, int results_length)
 {
     float sum_weights = array_sum(weights, n_dists);
     float* normalized_weights = malloc(n_dists * sizeof(float));
     for (int i = 0; i < n_dists; i++) {
         normalized_weights[i] = weights[i] / sum_weights;
     }
 
     float* cummulative_weights = malloc(n_dists * sizeof(float));
     array_cumsum(normalized_weights, cummulative_weights, n_dists);
 
     //create var holders
     float p1;
     int sample_index, i, own_length;
 
     {
 			for (int i = 0; i < results_length; i++) {
 					p1 = random_uniform(0, 1);
 					for (int j = 0; j < n_dists; j++) {
 							if (p1 < cummulative_weights[j]) {
 									results[i] = samplers[j]();
 									break;
 							}
 					}
 			}
     }
     free(normalized_weights);
     free(cummulative_weights);
 }
 
 float sample_0()
 {
     return 0;
 }
 
 float sample_1()
 {
     return 1;
 }
 
 float sample_few()
 {
     return random_to(1, 3);
 }
 
 float sample_many()
 {
     return random_to(2, 10);
 }
 
 int main()
 {
     //initialize randomness
     srand(1);
     
 		// clock_t start, end;
 		// start = clock();
 
 		// Toy example
 		// Declare variables in play
 		float p_a, p_b, p_c;
 		// printf("Max threads: %d\n", n_threads);
 		// omp_set_num_threads(n_threads);
 
 		// Initialize variables
 		p_a = 0.8;
 		p_b = 0.5;
 		p_c = p_a * p_b;
 
 		// Generate mixture
 		int n_dists = 4;
 		float weights[] = { 1 - p_c, p_c / 2, p_c / 4, p_c / 4 };
 		float (*samplers[])(void) = { sample_0, sample_1, sample_few, sample_many };
 
 		float* results = malloc(N * sizeof(float));
 		mixture(samplers, weights, n_dists, results, N);
 		printf("Sum(dist_mixture, N)/N = %f\n", array_sum(results, N) / N);
 		// array_print(dist_mixture[0], N);
 		
 		// end = clock();
 		// printf("Time (ms): %f\n", ((double)(end - start)) / (CLOCKS_PER_SEC * 1000));
 		// ^ Will only measure how long it takes the inner main to run, not the whole program, 
 		// including e.g., loading the program into memory or smth.
 		// Also CLOCKS_PER_SEC in POSIX is a constant equal to 1000000.
 		// See: https://stackoverflow.com/questions/10455905/why-is-clocks-per-sec-not-the-actual-number-of-clocks-per-second
     return 0;
 }