Shell sort algorithm

This is almost as fast as quicksort in most cases. Attempts to make this faster failed including a test and early out.

void ShellSort (int array[], int num)
{
   int inc = num/2;
   while (inc > 0)
   {
       for (int i=inc; i < num-1; i++)
       {
           int temp = array[i];
           int j=i;
           while (j>= inc && temp < array [j-inc])
           {
               array[j] = array[j-inc];
               j -= inc;
           }
           array [j] = temp;
       }
       inc = inc/2.2;  // note the subdivision value which could be 2, but 2.2 is better
   }
}