geometric-acceptance

Aurox_

May 18th, 2025 (edited)

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C 1.32 KB | Science | 0 0

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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#define ARG_NUM 4
double ran_cos(void);
int main(int argc, char *argv[ARG_NUM]) {
double r, d, cos_theta, cos_theta_crit, ratio, expected_ratio;
int n;
unsigned int counts, i;
srand(time(NULL));
if (argc != ARG_NUM) {
fprintf(stderr, "Usage: %s <number of points> <radius> <distance>\n", argv[0]);
return 1;
}
n = atoi(argv[1]);
r = atof(argv[2]);
d = atof(argv[3]);
if (n <= 0) {
fprintf(stderr, "Number of points must be a positive integer.\n");
return 1;
}
if (r <= 0 || d <= 0) {
fprintf(stderr, "Radius and distance must be positive numbers.\n");
return 1;
}
cos_theta_crit = d / sqrt(r * r + d * d);
printf("Critical cos(theta): %f\n", cos_theta_crit);
for (i = 0, counts = 0; i < n; i++) {
cos_theta = ran_cos();
if (cos_theta > cos_theta_crit) {
counts++;
}
}
ratio = ((float)counts) / n;
expected_ratio = 0.5 * (1 - cos_theta_crit);
printf("Total points: %d\nTotal hits: %d\nRatio: %.6f\nExpected ratio: %.6f\n", n, counts, ratio, expected_ratio);
return 0;
}
double ran_cos(void) {
return 1 - 2 * ((double)rand() / RAND_MAX);
}

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