```
1 编译运行附件中的代码，提交运行结果截图，并说明程序功能
2 修改代码，把同步资源个数减少为3个，把使用资源的线程增加到 （你的学号%3 + 4）个，编译代码，提交修改后的代码和运行结果截图。
```
```c
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <semaphore.h>
#define NUM 5
int queue[NUM];
sem_t blank_number, product_number;
void *producer ( void * arg )
{
static int p = 0;
for ( ;; ) {
sem_wait( &blank_number );
queue[p] = rand() % 1000;
printf("Product %d
", queue[p]);
p = (p+1) % NUM;
sleep ( rand() % 5);
sem_post( &product_number );
}
}
void *consumer ( void * arg )
{
static int c = 0;
for( ;; ) {
sem_wait( &product_number );
printf("Consume %d
", queue[c]);
c = (c+1) % NUM;
sleep( rand() % 5 );
sem_post( &blank_number );
}
}
int main(int argc, char *argv[] )
{
pthread_t pid, cid;
sem_init( &blank_number, 0, NUM );
sem_init( &product_number, 0, 0);
pthread_create( &pid, NULL, producer, NULL);
pthread_create( &cid, NULL, consumer, NULL);
pthread_join( pid, NULL );
pthread_join( cid, NULL );
sem_destroy( &blank_number );
sem_destroy( &product_number );
return 0;
}
```
功能：每一个生产者都要把自己生产的产品放入缓冲池，每个消费者从缓冲池中取走产品消费。在这种情况下，生产者消费者进程同步，因为只有通过互通消息才知道是否能存入产品或者取走产品。他们之间也存在互斥，即生产者消费者必须互斥访问缓冲池，即不能有两个以上的进程同时进行。
2.
```c
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <semaphore.h>
#define NUM 3
int queue[NUM];
sem_t blank_number, product_number;
void *producer ( void * arg )
{
static int p = 0;
for ( ;; ) {
sem_wait( &blank_number );
queue[p] = rand() % 6;
printf("Product %d
", queue[p]);
p = (p+1) % NUM;
sleep ( rand() % 5);
sem_post( &product_number );
}
}
void *consumer ( void * arg )
{
static int c = 0;
for( ;; ) {
sem_wait( &product_number );
printf("Consume %d
", queue[c]);
c = (c+1) % NUM;
sleep( rand() % 5 );
sem_post( &blank_number );
}
}
int main(int argc, char *argv[] )
{
pthread_t pid, cid;
sem_init( &blank_number, 0, NUM );
sem_init( &product_number, 0, 0);
pthread_create( &pid, NULL, producer, NULL);
pthread_create( &cid, NULL, consumer, NULL);
pthread_join( pid, NULL );
pthread_join( cid, NULL );
sem_destroy( &blank_number );
sem_destroy( &product_number );
return 0;
}
```