多线程计算----pthread

#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <pthread.h>

#include <time.h>

#define NUM_THREADS 10

#define buffer_size 6000000

void *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);

}