code: protected void rebuild() {
  		mandatoryArcsList.clear();
  		ISet nei;
  		for (int i = 0; i < n; i++) {
  			nei = gV.getMandNeighOf(i);
  			for (int j : nei) {
  				if (i < j) {
  					mandatoryArcsList.add(i * n + j);
  				}
  			}
  		}
  	}
docs: ***********************************************************************************