nth4

#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>




int thread_num = 1;
long vector_length = 100000;
int total = 0;
int *a = NULL;


void *vel_mul(void *arg);


int main(int argc, char *argv[]){
int res;
void *thread_result;
//scan income
if(argc != 3){
printf("You have not enter enough parameters. So using default parameter\n");
}
else{
thread_num = atoi(argv[1]);
vector_length = atol(argv[2]);
}
printf("Thread number is %d. Vector length is %ld\n",thread_num,vector_length);
//scan finished


//start create threads
a = (int *)calloc(vector_length,sizeof(int));
for(int i = 0; i < vector_length; i++){
switch((i+1)%3){
case 0 :
a[i]=1;
break;
case 1 :
a[i]=-1;
break;
case 2 :
a[i]=0;
break;
}
}
pthread_t *a_thread;
a_thread = (pthread_t *)calloc(thread_num,sizeof(pthread_t));


for(int i = 0; i < thread_num; i++){
res = pthread_create(&a_thread[i],NULL,vel_mul,(void *)&i);
if(res != 0)perror("thread creation failed");
}


printf("Waiting ...\n");


for(int i = thread_num-1; i >=0; i--){
res = pthread_join(a_thread[i],&thread_result);
}
printf("finish \n");
printf("total is %d\n",total);