How to copy values from one vector to another quickly

I'm making a question that the number of elements in the vector are in 10 ^ 6 and just wanted to copy certain element to it only I did the normal but common way, is there another possibility if I make the copy faster? >

for(i = 0; i < teste; i++)
{
    if(primo(vetor[i]))
    {
       aux[cont] = vetor[i];
       cont++;
    }
}

Algorithm to find the prime number

int primo(int num)
{
  int pri = 1, i, raiz = sqrt(num);
  if(num == 2)
  {
    return 1;
  }
  if (num == 1 || num == 0 || num % 2 == 0)
  {
    return 0;
  }
  for(i = 3; i <= raiz; i += 2)
  {
     if(num % i == 0)
     {
         pri = 0;
         break;
     }
  }
   return pri;
}