pingpong.c

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

int N = 100000;
//int N = 20;

pthread_mutex_t ping_lock = PTHREAD_MUTEX_INITIALIZER, pong_lock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t ping_cond, pong_cond;
pthread_t ping_thread, pong_thread;
int can_ping = 1, can_pong = 0;

void *pingfunc(void *arg) {
	int i;
	for (i = 0; i < N; ++i) {
		pthread_mutex_lock(&ping_lock);
		while(!can_ping) {
			pthread_cond_wait(&ping_cond, &ping_lock);
		}
		pthread_mutex_unlock(&ping_lock);
		
		can_ping = 0;
		//printf("ping!\n");
		
		pthread_mutex_lock(&pong_lock);
		can_pong = 1;
		pthread_cond_signal(&pong_cond);
		pthread_mutex_unlock(&pong_lock);
	}
	
}

void *pongfunc(void *arg) {
	int i;
	for (i = 0; i < N; ++i) {
		pthread_mutex_lock(&pong_lock);
		while(!can_pong) {
			pthread_cond_wait(&pong_cond, &pong_lock);
		}
		pthread_mutex_unlock(&pong_lock);
		
		can_pong = 0;
		//printf("pong!\n");
		
		pthread_mutex_lock(&ping_lock);
		can_ping = 1;
		pthread_cond_signal(&ping_cond);
		pthread_mutex_unlock(&ping_lock);
	}
}

int main(void) {
	struct timespec t0, t1;
	clock_gettime(CLOCK_MONOTONIC, &t0);
	pthread_cond_init(&ping_cond, NULL);
	pthread_cond_init(&pong_cond, NULL);
	pthread_create(&ping_thread, NULL, pingfunc, NULL);
	pthread_create(&pong_thread, NULL, pongfunc, NULL);
	
	pthread_join(ping_thread, NULL);
	pthread_join(pong_thread, NULL);
	clock_gettime(CLOCK_MONOTONIC, &t1);
	
	double d = (double)(t1.tv_sec - t0.tv_sec) + 1.0e-9 * (double)(t1.tv_nsec - t0.tv_nsec);
	printf("%.10f seconds per pingpong (total %.5f)\n", d/ N, d);
}