thread4.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>

#define NUM_THREAD 100
void *thread_inc(void*arg);
void *thread_des(void*arg);
long long num=0;

int main(int argc, char const *argv[])
{
	pthread_t thread_id[NUM_THREAD];
	int i;
	
	printf("size of long long : %ld\n", sizeof(long long));
	for (i = 0; i < NUM_THREAD; ++i)
	{
		if(i%2)
			pthread_create(&thread_id[i],NULL, thread_inc, NULL);
		else
			pthread_create(&thread_id[i],NULL, thread_des, NULL);
	}

	for (i = 0; i < NUM_THREAD; ++i)
	{
		pthread_join(thread_id[i],NULL);

	}

	printf("result: %lld\n", num);
	return 0;
}

void *thread_inc(void *arg)
{
	int i;
	for (i = 0; i < 50000000; ++i)
	{
		num+=1;
	}
	return NULL;
}
void *thread_des(void *arg)
{
	int i;
	for (i = 0; i < 50000000; ++i)
	{
		num-=1;
	}
	return NULL;
}