Calling a void* function from main in C - c

Question

Currently I am working on a program that uses threads to calculate the sum of square roots. My program works, however one of the requirements is to use the main thread to find the initial value, and as soon as I call the function Void *calc from main, the program breaks. Is there a certain way to make such a function call? Is this because the function is a pointer? Any help is appreciated.
#include <pthread.h>
#include <stdio.h>
#include <math.h>
#include <unistd.h>
#define NUM_THREADS 3
int ARGV;
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
double total = 0;
void *calc(void* t){
int ph = (int)t + 1;
int start, stop, interval_size;
interval_size = ARGV/(NUM_THREADS + 1);
start = ((ph) * interval_size) + 1;
stop = (ph * interval_size) + 1;
double ttl;
int i;
for (i = start; i <= stop; i++){
ttl = ttl + sqrt(i);
printf("Total Thread %i %lf\n", ph, ttl);
}
pthread_mutex_lock(&m);
total = total + ttl;
pthread_mutex_unlock(&m);
pthread_exit(NULL);
}
int main(int argc, char* argv[]) {
int i;
double ttl;
ARGV = atoi(argv[1]);
pthread_t ti[NUM_THREADS];
calc(0);
for (i = 0; i < NUM_THREADS; i++) {
pthread_create(&ti[i], NULL, calc,(void *)i);
}
/*for (i = 1; i <= (ARGV / 4) ; i++){
ttl = ttl + sqrt(i);
}*/
for (i = 0; i < NUM_THREADS; i++) {
pthread_join(ti[i], NULL);
}
total = total + ttl;
printf("Result: %lf\n", total);
}
The program breaks as in the function seems to only be called once, instead of each thread using the function. The only value printed out is some vague incorrect number.

Answer 1

Your calc function does pthread_exit. Now pthread_exit can and should be called from the main thread, so that's fine
To allow other threads to continue execution, the main thread
should terminate by calling pthread_exit() rather than exit(3).
But since this happens before any other thread has been created, the program just exits straight away, without ever starting other threads.