Multithreading in C in Different CPU core

# define _GNU_SOURCE
# include <stdio.h>
# include <math.h>
# include <stdlib.h>
# include <pthread.h>
# include <stdlib.h>

pthread_mutex_t mux = PTHREAD_MUTEX_INITIALIZER;


struct p2p{
int st;
int en;
};

void *primeChk(void* val);

int main()
{
  pthread_t thread1,thread2,thread3,thread4;
  struct p2p valu1,valu2,valu3,valu4;
  int j,ret1,ret2,ret3,ret4;
  cpu_set_t cpuset;

// pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset);


  valu1.st = 1;
  valu1.en = 5000;
  valu2.st = 5001;
  valu2.en = 10000;
  valu3.st = 10001;
  valu3.en = 15000;
  valu4.st = 15001;
  valu4.en = 20000;

   // initialization
   CPU_ZERO(&cpuset);


   CPU_SET(0,&cpuset);
   pthread_setaffinity_np(thread1, sizeof(cpu_set_t), &cpuset);
   ret1 = pthread_create(&thread1,NULL,&primeChk,(void*)&valu1);
   //CPU_ZERO(&cpuset); 

   CPU_SET(1,&cpuset);
   pthread_setaffinity_np(thread2, sizeof(cpu_set_t), &cpuset);
   ret2 = pthread_create(&thread2,NULL,&primeChk,(void*)&valu2);
  // CPU_ZERO(&cpuset);
/*      
    CPU_SET(2,&cpuset);
    pthread_setaffinity_np(thread3, sizeof(cpu_set_t), &cpuset);
    ret3 = pthread_create(&thread3,NULL,&primeChk,(void*)&valu3);
   
   CPU_SET(3,&cpuset);
   pthread_setaffinity_np(thread4, sizeof(cpu_set_t), &cpuset);
   ret4 = pthread_create(&thread4,NULL,&primeChk,(void*)&valu4);
  */

  pthread_join(thread1,NULL);
  pthread_join(thread2,NULL);
 // pthread_join(thread3,NULL);
 // pthread_join(thread4,NULL);

  return 0;
}


void *primeChk(void *val)
{
  struct p2p *valu = (struct p2p *)val;
  int str,end,i,k,j,l,m;

 // pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset);
  str = valu->st;
  end = valu->en;
  if(str == 1)
  printf("%d",++str);

  pthread_mutex_lock(&mux);
  for(i=str;i<=end;i++)
  {
     k = sqrt(i);l = 0;
     for(j=2;j<=k+1;j++)
     if(i % j == 0)
     {
        l = 1;break;
     }
     if(l == 0)printf(" %d",i);
  }
  pthread_mutex_unlock(&mux);

  //pthread_getaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset);
 // printf("\nSet returned by pthread_getaffinity_np() contained:\n");
 // for (j = 0; j < CPU_SETSIZE; j++)
   //    if (CPU_ISSET(j, &cpuset))
    //   printf("    CPU %d\n", j);


}