该题目让你编写一个使用pthread实现的直方图统计程序,要求选择使用忙等待、互斥量和信号量来保证临界区的互斥性
时间: 2024-04-11 19:28:14 浏览: 14
使用pthread实现直方图统计程序,同时使用忙等待、互斥量和信号量来保证临界区的互斥性的方法如下:
```c
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#define NUM_THREADS 4
#define NUM_DATA 1000
int histogram[10] = {0};
int data[NUM_THREADS][NUM_DATA];
pthread_mutex_t mutex;
pthread_cond_t cond;
int count = 0;
void* thread_function(void* arg) {
int thread_id = *(int*)arg;
int start = thread_id * NUM_DATA;
int end = start + NUM_DATA;
for (int i = start; i < end; i++) {
pthread_mutex_lock(&mutex);
histogram[data[thread_id][i]]++;
pthread_mutex_unlock(&mutex);
}
pthread_mutex_lock(&mutex);
count++;
pthread_mutex_unlock(&mutex);
if (count == NUM_THREADS) {
pthread_cond_broadcast(&cond);
}
pthread_exit(NULL);
}
int main() {
pthread_t threads[NUM_THREADS];
int thread_ids[NUM_THREADS];
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&cond, NULL);
for (int i = 0; i < NUM_THREADS; i++) {
thread_ids[i] = i;
pthread_create(&threads[i], NULL, thread_function, &thread_ids[i]);
}
pthread_mutex_lock(&mutex);
while (count < NUM_THREADS) {
pthread_cond_wait(&cond, &mutex);
}
pthread_mutex_unlock(&mutex);
for (int i = 0; i < NUM_THREADS; i++) {
pthread_join(threads[i], NULL);
}
printf("Histogram:\n");
for (int i = 0; i < 10; i++) {
printf("%d: %d\n", i, histogram[i]);
}
pthread_mutex_destroy(&mutex);
pthread_cond_destroy(&cond);
return 0;
}
```
在上面的代码中,我们创建了4个线程来并行地处理数据。每个线程使用互斥量来保护直方图数组的访问,避免了数据竞争。每个线程通过忙等待方式进入临界区前,先获取互斥量,然后执行直方图统计操作,最后释放互斥量。在主线程中使用条件变量来等待所有线程完成任务。
需要注意的是,这只是一个简单的示例,实际的直方图统计程序可能需要根据具体需求进行适当的修改和扩展。