docs: public int rank() {
      final double eps = 0x1p-52, tol = (m > n ? m : n) * s[0] * eps;
      int r = 0;
      for(int i = 0; i < s.length; i++) {
        if(s[i] > tol) {
          r++;
        }
      }
      return r;
    }