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#include <stdio.h>
#if defined(PROG_SINUS_SUM)
#define EPSILON 0.001*0.001
#define MAX_ITERATIONS 100
int main(void) {
puts("defined macro PROG_SINUS_SUM");
double x;
double result;
double last_elem;
int i;
printf("Input a number\n");
scanf("%lf", &x);
last_elem = result = x;
for (i = 1; i < MAX_ITERATIONS; ++i) {
last_elem = last_elem * x * x / (2*i * (2*i+1));
if (last_elem*last_elem <= EPSILON) break;
result += last_elem * ( (i%2 * -2) + 1 );
}
printf("result = %lf; iterations = %i; last_elem = %lf\n", result, i, last_elem);
return 0;
}
#elif defined(PROG_MONTE_CARLO)
#include <stdlib.h>
#include <time.h>
#define _USE_MATH_DEFINES
#include <math.h>
struct point {
float x, y;
};
struct circle {
// center not needed for this task
/*struct point center;*/
float rad;
};
char in_circle(const struct circle *c, const struct point p) {
/*p.x -= c->x;*/
/*p.y -= c->y;*/
return p.x * p.x + p.y * p.y < c->rad*c->rad;
}
float calculate_pi(int iterations) {
int in = 0, out = 0;
int *arr[2] = {&out, &in};
const struct circle c = {.rad = 1.0f};
for (int i = 0; i < iterations; ++i) {
struct point p = {
.x = rand() % 2000000u / 1e6f - 1,
.y = rand() % 2000000u / 1e6f - 1
};
++*arr[in_circle(&c, p)];
}
return (float)in/iterations * 4;
}
int main(int argc, char *argv[]) {
puts("defined macro PROG_MONTE_CARLO");
srand(time(NULL));
int iters;
if (argc == 2) {
iters = atoi(argv[1]);
} else {
fputs("Iterations: ", stdout);
if (!scanf("%i", &iters)) {
fputs("Input a valid number\n", stderr);
return EXIT_FAILURE;
}
}
float pi = calculate_pi(iters);
float err = fabs(M_PI-pi)/M_PI;
printf( "calculated pi: %.4f, actual pi: %.4f\n"
"error: %.2f%%\n",
pi, M_PI, err * 100);
return EXIT_SUCCESS;
}
#else
#error "define macro PROG_SINUS_SUM or PROG_MONTE_CARLO in compilation flags"
#endif
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