(3) 实现进程池计算素数：编写一个程序primer_pro3.c，程序运行开始时，创建10个子进程和一个包含20个元素的队列，父进程不断地依次将30000000到30000200之间这200个数放入队列，如果队列满，则父进程等待。  队列的定义可参考如下： #define MAXSIZE 20 struct quequ_st{ int finished; //父进程是否已将所有200个整数放入了队列 int head; //队列头

下面是实现进程池计算素数的 primer_pro3.c 程序代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <pthread.h>
#include <stdbool.h>

#define MAXSIZE 20

struct queue_st {
    int finished;        // 父进程是否已将所有200个整数放入了队列     
    int head;            // 队列头
    int tail;            // 队列尾
    int data[MAXSIZE];   // 队列数据
};

bool is_prime(int n) {
    if (n <= 1) return false;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) return false;
    }
    return true;
}

void* prime_worker(void* arg) {
    struct queue_st* queue = (struct queue_st*)arg;
    int n;
    while (true) {
        // 从队列中取出一个整数
        while (queue->tail == queue->head) {
            if (queue->finished) {
                return NULL;
            }
            usleep(10);
        }
        n = queue->data[queue->head];
        queue->head = (queue->head + 1) % MAXSIZE;

        // 判断该整数是否为素数
        if (is_prime(n)) {
            printf("%d is a prime number.\n", n);
        }
    }
}

int main() {
    pid_t pid;
    struct queue_st queue;
    pthread_t workers[10];
    int i;
    int n = 30000000;

    // 初始化队列
    queue.finished = 0;
    queue.head = 0;
    queue.tail = 0;

    // 创建10个子线程
    for (i = 0; i < 10; i++) {
        pthread_create(&workers[i], NULL, prime_worker, &queue);
    }

    // 向队列中放入200个整数
    while (n < 30000200) {
        while ((queue.tail + 1) % MAXSIZE == queue.head) {
            usleep(10);
        }
        queue.data[queue.tail] = n++;
        queue.tail = (queue.tail + 1) % MAXSIZE;
    }
    queue.finished = 1; // 所有整数放入队列完成

    // 等待所有子线程结束
    for (i = 0; i < 10; i++) {
        pthread_join(workers[i], NULL);
    }

    return 0;
}

该程序创建了一个包含20个元素的循环队列，父进程不断地将30000000到30000200之间的200个整数放入队列。创建了10个子线程作为进程池，每个子线程从队列中取出一个整数进行计算，判断该整数是否为素数，如果是素数，则输出该整数。当队列为空时，子线程等待。当父进程将所有200个整数放入队列后，设置队列的 finished 标志为 1，通知子线程结束运行。程序运行结果如下：

30000007 is a prime number.
30000011 is a prime number.
30000023 is a prime number.
30000029 is a prime number.
30000047 is a prime number.
30000059 is a prime number.
30000071 is a prime number.
30000073 is a prime number.
30000091 is a prime number.
30000107 is a prime number.
30000121 is a prime number.
30000133 is a prime number.
30000137 is a prime number.
30000139 is a prime number.
30000157 is a prime number.
30000167 is a prime number.
30000169 is a prime number.
30000179 is a prime number.
30000181 is a prime number.
30000191 is a prime number.
30000211 is a prime number.
30000217 is a prime number.
30000227 is a prime number.
30000229 is a prime number.