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Unix Threads in C

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Thread Pools in C (using the PTHREAD API)

#include <stdio.h> #include <string.h> #include <pthread.h> #include <stdlib.h> #include <unistd.h> #include <time.h> #define THREAD_NUM 4 typedef struct Task { int a, b; } Task; Task taskQueue[256]; int taskCount = 0; pthread_mutex_t mutexQueue; pthread_cond_t condQueue; void executeTask(Task* task) { usleep(50000); int result = task->a + task->b; printf("The sum of %d and %d is %d\n", task->a, task->b, result); } void submitTask(Task task) { pthread_mutex_lock(&mutexQueue); taskQueue[taskCount] = task; taskCount++; pthread_mutex_unlock(&mutexQueue); pthread_cond_signal(&condQueue); } // 1 2 3 4 5 // 2 3 4 5 void* startThread(void* args) { while (1) { Task task; pthread_mutex_lock(&mutexQueue); while (taskCount == 0) { pthread_cond_wait(&condQueue, &mutexQueue); } task = taskQueue[0]; int i; for (i = 0; i < taskCount - 1; i++) { taskQueue[i] = taskQueue[i + 1]; } taskCount--; pthread_mutex_unlock(&mutexQueue); executeTask(&task); } } int main(int argc, char* argv[]) { pthread_t th[THREAD_NUM]; pthread_mutex_init(&mutexQueue, NULL); pthread_cond_init(&condQueue, NULL); int i; for (i = 0; i < THREAD_NUM; i++) { if (pthread_create(&th[i], NULL, &startThread, NULL) != 0) { perror("Failed to create the thread"); } } srand(time(NULL)); for (i = 0; i < 100; i++) { Task t = { .a = rand() % 100, .b = rand() % 100 }; submitTask(t); } for (i = 0; i < THREAD_NUM; i++) { if (pthread_join(th[i], NULL) != 0) { perror("Failed to join the thread"); } } pthread_mutex_destroy(&mutexQueue); pthread_cond_destroy(&condQueue); return 0; }