多线程计算----pthread-白红宇

多线程计算----pthread

阅读量：6912 次

发布时间：2019-06-27

本文共 2475 字，大约阅读时间需要 8 分钟。

#include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         #define NUM_THREADS 10 #define buffer_size 6000000void *thread_function(void *agr);int buffer[buffer_size];int result[NUM_THREADS];int result1[NUM_THREADS];int main() {	int res;	pthread_t a_thread[NUM_THREADS];	void *thread_result;	int lots_of_threads;	//static int buffer[60];	int i, m;	int tmp1;	int flag = 1;	struct timeval tv_start, tv_end;	//static int result[10];	for(i = 0; i < buffer_size; i++) {		buffer[i] = (int)rand() % 10000;	}	gettimeofday(&tv_start, NULL);	for(i = 0; i < NUM_THREADS; i++) {		tmp1 = 0;		for(m = 0; m < buffer_size / NUM_THREADS; m++){			if(tmp1 < buffer[i * 10 + m])				tmp1 = buffer[i * 10 + m];		}		result1[i] = tmp1;	}	gettimeofday(&tv_end, NULL);	printf("Cost Time: %0.10fms\n", (float)((1000000 * (tv_end.tv_sec - tv_start.tv_sec) + tv_end.tv_usec - tv_start.tv_usec)/1000));	for(lots_of_threads = 0; lots_of_threads < NUM_THREADS; lots_of_threads++) {		res = pthread_create(&(a_thread[lots_of_threads]), NULL, thread_function, (void*)lots_of_threads);		if(res != 0) {			perror("Thread creation failed");			exit(EXIT_FAILURE);		}		//sleep(1);	}	printf("Waiting for threads to finish.....\n");	for(lots_of_threads = NUM_THREADS - 1; lots_of_threads >= 0; lots_of_threads--) {		res = pthread_join(a_thread[lots_of_threads], &thread_result);		if(res == 0) {			printf("Picked up a thread\n");		} else {			perror("Pthread_join failed");		}	}	for(m = 0; m < NUM_THREADS; m++) {		if(result[m] != result1[m])			flag = 0;	}  if(!flag)		printf("Compute wrong~~~\n");	else		printf("Successful~~~\n");		printf("All done\n");}void *thread_function(void *arg) {	//int my_number = *(int*) arg;	int my_number = (int)arg;	int rand_num;	int k;  int tmp = 0;	struct timeval tv_start, tv_end;  gettimeofday(&tv_start, NULL);	for(k = 0; k < buffer_size / NUM_THREADS; k++) {		if(tmp < buffer[my_number * (buffer_size / NUM_THREADS) + k])			tmp = buffer[my_number * (buffer_size / NUM_THREADS) + k];	}	result[my_number] = tmp;	gettimeofday(&tv_end, NULL);	printf("Thread %d Cost Time: %0.10fms\n", my_number, (float)((1000000 * (tv_end.tv_sec - tv_start.tv_sec) + tv_end.tv_usec - tv_start.tv_usec)/1000));	printf("thread_function is running. Argument was %d\n", my_number);	//rand_num = 1 + (int)(9.0 * rand() / (RAND_MAX + 1.0));	//sleep(rand_num);	//printf("Rand number %d\n", rand_num);	//printf("Byte from %d\n", my_number);	pthread_exit(NULL);}