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Calculate Pi with Leibniz formula using pthread library (as part of C course)
#include<stdio.h>
#include<pthread.h>
#include<math.h>
#include<stdlib.h>
#include<unistd.h>
#define NUM_THREADS 8
typedef struct {
int rank;
double sum;
} thread_data;
thread_data td[NUM_THREADS];
void* help_pi(void *rank) {
int thread_rank = *(int *)rank;
double incr = 0;
int sign;
int k = thread_rank;
if (k % 2) {
sign = -1;
} else {
sign = 1;
}
td[thread_rank].sum = 4*((double)sign / (2 * thread_rank + 1));
do {
k += NUM_THREADS;
if (k % 2) {
sign = -1;
} else {
sign = 1;
}
incr = (double)sign / (2 * k + 1);
td[thread_rank].sum += 4 * incr;
}
while ( fabs(incr) > 1e-6);
return NULL;
}
int main(){
int rank = 0;
int err;
double pi = 0;
pthread_t thread_ids[NUM_THREADS];
while(rank < NUM_THREADS) {
td[rank].rank = rank;
err = pthread_create(&(thread_ids[rank]), NULL, help_pi, (void*)&td[rank].rank);
if (err != 0) {
printf("Can't create thread error =%d\n", err);
return 1;
}
rank++;
}
rank = 0;
while(rank < NUM_THREADS) {
pthread_join(thread_ids[rank], NULL);
rank++;
}
rank = 0;
while(rank < NUM_THREADS) {
pi += td[rank].sum;
rank++;
}
printf("%f\n",pi);
return 0;
}
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