monitor.cpp

linux下多线程实现生产者消费者及用并行算法求圆周率等经典算法

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

using namespace std;

#define QSIZE 8

class monitor 
{
private:
     pthread_cond_t full; /* count the number of characters in the queue */
     pthread_cond_t empty;/* count the number of empty slots */
     pthread_mutex_t m;   /* implements the critical section */
     unsigned int iBuf;   /* the tail of the circular queue */
     unsigned int oBuf;   /* the head of the circular queue */
     int count;           /* count characters */
     char buf [QSIZE];    /* the circular queue */
	
public:
     monitor() 
	  {
	       oBuf = 0; iBuf = 0; count=0;      /* head and tail match when queue empty */
	       pthread_cond_init(&full, NULL);   /* no characters stored yet */
	       pthread_cond_init(&empty, NULL);  /* all character slots are empty */
	       pthread_mutex_init(&m, NULL);
	  }
     ~monitor() 
	  {
	       pthread_mutex_destroy(&m);
	  }
     void put(char ch) /* add "ch" to circular queue; wait if full */
	  {
	       pthread_mutex_lock(&m);
	       while (count >= QSIZE) pthread_cond_wait(&empty, &m); /* is there an empty slot? */
	       buf[iBuf] = ch;              /* store the character */
	       iBuf = (iBuf+1) % QSIZE;     /* increment to QSIZE, then reset to 0 */
	       cout << "put to buf[" << iBuf << "]" << endl;
	       count++;
	       pthread_cond_signal(&full); /* a new character is available */
	       pthread_mutex_unlock(&m);
	  }
     char get() /* remove "ch" from queue; wait if empty */
	  {
	       char ch;
	       pthread_mutex_lock(&m);
	       while (count <= 0) pthread_cond_wait(&full, &m); /* is a character present? */
	       ch = buf[oBuf];              /* retrieve from the head of the queue */
	       oBuf = (oBuf+1) % QSIZE;
	       cout << "get from buf[" << oBuf << "]" << endl;
	       count--;
	       pthread_cond_signal(&empty); /* signal existence of new empty slot */
	       pthread_mutex_unlock(&m);
	       return ch;
	  }
};

void *producer(void *arg)
{
     monitor *mon = (class monitor *)arg;
     while (1) { mon->put('a'); sleep(1); }
     return NULL;
}
void *consumer(void *arg)
{
     monitor *mon = (class monitor *)arg;
     while (1) { mon->get(); sleep(1); }
     return NULL;
}

int main()
{
     monitor *mon = new monitor;
     pthread_t tid[3];
     void *retval;
	
     pthread_create(&tid[0], NULL, producer, (void*)mon);
     pthread_create(&tid[1], NULL, producer, (void*)mon);
     pthread_create(&tid[2], NULL, consumer, (void*)mon);

     pthread_join(tid[0], &retval);
     pthread_join(tid[1], &retval);
     pthread_join(tid[2], &retval);
	
     delete mon;
     return 0;
}