docs: private double er(Front front, Front referenceFront) throws JMetalException {
      int numberOfObjectives = referenceFront.getPointDimensions() ;
      double sum = 0;
  
      for (int i = 0; i < front.getNumberOfPoints(); i++) {
        Point currentPoint = front.getPoint(i);
        boolean thePointIsInTheParetoFront = false;
        for (int j = 0; j < referenceFront.getNumberOfPoints(); j++) {
          Point currentParetoFrontPoint = referenceFront.getPoint(j);
          boolean found = true;
          for (int k = 0; k < numberOfObjectives; k++) {
            if(currentPoint.getValue(k) != currentParetoFrontPoint.getValue(k)){
              found = false;
              break;
            }
          }
          if(found){
            thePointIsInTheParetoFront = true;
            break;
          }
        }
        if(!thePointIsInTheParetoFront){
          sum++;
        }
      }
  
      return sum / front.getNumberOfPoints();
    }