用VI编辑器编写生产者-消费者问题模拟算法

生产者-消费者问题是经典的并发问题，下面是一个用VI编辑器编写的模拟算法：

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

#define BUFFER_SIZE 10 // 缓冲区大小
#define PRODUCER_NUM 3 // 生产者数量
#define CONSUMER_NUM 2 // 消费者数量

int buffer[BUFFER_SIZE]; // 缓冲区
int in = 0, out = 0; // 缓冲区读写指针
int count = 0; // 缓冲区中的产品数量

pthread_mutex_t mutex; // 互斥锁
pthread_cond_t full; // 缓冲区满条件变量
pthread_cond_t empty; // 缓冲区空条件变量

// 生产者线程函数
void *producer(void *arg) {
    int id = *(int *)arg;
    while (1) {
        pthread_mutex_lock(&mutex);
        while (count == BUFFER_SIZE) { // 缓冲区满，等待消费者消费
            printf("Producer %d: Buffer is full, waiting for consumer...\n", id);
            pthread_cond_wait(&full, &mutex);
        }
        int item = rand() % 100; // 生产一个产品
        buffer[in] = item;
        printf("Producer %d: Produced item %d into buffer.\n", id, item);
        in = (in + 1) % BUFFER_SIZE; // 更新缓冲区写指针
        count++;
        pthread_cond_signal(&empty); // 通知消费者可以消费了
        pthread_mutex_unlock(&mutex);
        sleep(1);
    }
}

// 消费者线程函数
void *consumer(void *arg) {
    int id = *(int *)arg;
    while (1) {
        pthread_mutex_lock(&mutex);
        while (count == 0) { // 缓冲区空，等待生产者生产
            printf("Consumer %d: Buffer is empty, waiting for producer...\n", id);
            pthread_cond_wait(&empty, &mutex);
        }
        int item = buffer[out];
        printf("Consumer %d: Consumed item %d from buffer.\n", id, item);
        out = (out + 1) % BUFFER_SIZE; // 更新缓冲区读指针
        count--;
        pthread_cond_signal(&full); // 通知生产者可以生产了
        pthread_mutex_unlock(&mutex);
        sleep(2);
    }
}

int main() {
    pthread_t pids[PRODUCER_NUM], cids[CONSUMER_NUM];
    int pargs[PRODUCER_NUM], cargs[CONSUMER_NUM];

    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&full, NULL);
    pthread_cond_init(&empty, NULL);

    // 创建生产者线程
    for (int i = 0; i < PRODUCER_NUM; i++) {
        pargs[i] = i + 1;
        pthread_create(&pids[i], NULL, producer, &pargs[i]);
    }

    // 创建消费者线程
    for (int i = 0; i < CONSUMER_NUM; i++) {
        cargs[i] = i + 1;
        pthread_create(&cids[i], NULL, consumer, &cargs[i]);
    }

    // 等待线程结束
    for (int i = 0; i < PRODUCER_NUM; i++) {
        pthread_join(pids[i], NULL);
    }
    for (int i = 0; i < CONSUMER_NUM; i++) {
        pthread_join(cids[i], NULL);
    }

    pthread_mutex_destroy(&mutex);
    pthread_cond_destroy(&full);
    pthread_cond_destroy(&empty);

    return 0;
}

上面的代码中，我们使用了互斥锁和条件变量来实现线程之间的同步和互斥。生产者线程会不断地往缓冲区中生产产品，当缓冲区满时会等待消费者消费；而消费者线程会不断地从缓冲区中消费产品，当缓冲区空时会等待生产者生产。这样可以保证生产者和消费者之间的同步和互斥，避免竞态条件和死锁问题的发生。