ordinal similarity

// see https://plus.google.com/u/0/112993898662880391149/posts/HDUTihJJHrk
int surfer(float* ke, float* pa, int is)
{
  int i1 = (is+1)/2 -1;
  int i2 = is -1;
  int i3 = i2/2*is;
  int i4 = i3 + i1;
  int i5 = i3 + i2;
  int i6 = i2*is;
  int i7 = i6 + i1;
  int i8 = is*is -1;

  int cmp1 = (ke[0] > ke[i1]) == (pa[0] > pa[i1]);
  int cmp2 = (ke[i1] > ke[i2]) == (pa[i1] > pa[i2]);
  int cmp3 = (ke[i3] > ke[i4]) == (pa[i3] > pa[i4]);
  int cmp4 = (ke[i4] > ke[i5]) == (pa[i4] > pa[i5]);
  int cmp5 = (ke[i6] > ke[i7]) == (pa[i6] > pa[i7]);
  int cmp6 = (ke[i7] > ke[i8]) == (pa[i7] > pa[i8]);

  return cmp1 + cmp2 + cmp3 + cmp4 + cmp5 + cmp6;
}