Order of printing numbers using thread synchronization-C++-php.cn

Order of printing numbers using thread synchronization

Here we will see how to print numbers in the correct order using different threads. Here we will create n threads and then synchronize them. The idea is that the first thread will print 1, then the second thread will print 2, and so on. When one thread tries to print, it locks the resource so other threads cannot use that part.

Example

#include  #include  #include  #include  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; pthread_cond_t* cond = NULL; int threads; volatile int count = 0; void* sync_thread(void* num) { //this function is used to synchronize the threads int thread_number = *(int*)num; while (1) { pthread_mutex_lock(&mutex); //lock the section if (thread_number != count) { //if the thread number is not same as count, put all thread except one into waiting state pthread_cond_wait(&cond[thread_number], &mutex); } printf("%d ", thread_number + 1); //print the thread number count = (count+1)%(threads); // notify the next thread pthread_cond_signal(&cond[count]); pthread_mutex_unlock(&mutex); } return NULL; } int main() { pthread_t* thread_id; volatile int i; int* thread_arr; printf("
Enter number of threads: "); scanf("%d", &threads); // allocate memory to cond (conditional variable) thread id's and array of size threads cond = (pthread_cond_t*)malloc(sizeof(pthread_cond_t) * threads); thread_id = (pthread_t*)malloc(sizeof(pthread_t) * threads); thread_arr = (int*)malloc(sizeof(int) * threads); for (i = 0; i < threads; i++) { //create threads thread_arr[i] = i; pthread_create(&thread_id[i], NULL, sync_thread, (void*)&thread_arr[i]); } // waiting for thread for (i = 0; i < threads; i++) { pthread_join(thread_id[i], NULL); } return 0; }

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Output

$ g++ test.cpp -lpthread $ ./a.out Enter number of threads: 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 ... ... ...

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