docs: static public double schwefel_102(double[] x) {
  
      double prev_sum, curr_sum, outer_sum;
  
      curr_sum = x[0];
      outer_sum = (curr_sum * curr_sum);
  
      for (int i = 1; i < x.length; i++) {
        prev_sum = curr_sum;
        curr_sum = prev_sum + x[i];
        outer_sum += (curr_sum * curr_sum);
      }
  
      return (outer_sum);
    }