code: private void init() {
          if (ERTs != null) return;
          synchronized (this) {
              if (ERTs != null) return;
              discretizeMasses();
              divideByGCD();
              computeLCMs();
              calcERT();
              computeErrors();
          }
      }
docs: Initializes the decomposer. Computes the extended residue table. This have to be done only one time for
  a given alphabet, independently from the masses you want to decompose. This method is called automatically
  if you compute the decompositions, so call it only if you want to control the time of the initialisation.