threads.c

#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <pthread.h>
#include <stdbool.h>

static bool is_prime(int n) {
	int i = 5;

	if (n < 2) return false;
	if (n % 2 == 0) return n == 2;
	if (n % 3 == 0) return n == 3;

	while (i * i <= n)
	{
		if (n % i == 0) return false;
		i += 2;
		if (n % i == 0) return false;
		i += 4;
	}

	return true;
}

void *thread_find_prime(void *data)
{
	int *repeats = data;
	for (int i = 0; i < *repeats; i++)
	{
		uint64_t startt = clock();
		const int start = 1;
		const int stop = 1000000;
		int sum = 0;
		int count = 0;
		int sc = 0;
		int p;

		for (p = start; p < stop; p++)
		{
			if (is_prime(p))
			{
				count++;
				sum += p;
				if (is_prime(sum))
				{
					sc++;
				}
			}
		}
		printf("%.2fms There are %d summerized primes in [%d, %d)\n", ((clock() - startt) / (double)CLOCKS_PER_SEC) * 1000, sc, start, stop);
	}
	return NULL;
}

int main(int a, char **args)
{
	uint64_t startt = clock();
  int threadcount = atoi(args[1]);
	pthread_t *threads = malloc(sizeof(pthread_t) * (unsigned)threadcount);
	int repeats = 10 / threadcount;
	for (int i = 0; i < threadcount; i++)
	{
		pthread_t *thread = threads + i;
		if (pthread_create(thread, NULL, thread_find_prime, &repeats)) exit(1);
	}
	for (int i = 0; i < threadcount; i++)
	{
		pthread_join(threads[i], NULL);
	}
	printf("%.2fms Total time\n", ((clock() - startt) / (double)CLOCKS_PER_SEC) * 1000);
	
}