private void mutateAddNode(Chromosome mutatee) {
    double nodeRandVal = nodeRand.nextDouble();
    ArrayList nodeLinks;
    // ArrayList nodes;
    NEATLinkGene chosen;
    NEATNodeGene newNode;
    NEATLinkGene newLower;
    NEATLinkGene newUpper;
    int newChromoIdx = mutatee.genes().length;
    // Gene[] newChromo = new Gene[newChromoIdx + 3];
    Gene[] newChromo = new Gene[newChromoIdx + 2];
    System.arraycopy(mutatee.genes(), 0, newChromo, 0, newChromoIdx);
    int linkIdx;

    if (nodeRandVal < this.pAddNode) {
      // add a node on an existing enabled connection
      // find an existing connection to intercept
      nodeLinks = this.candidateLinks(mutatee.genes(), true);
      if (nodeLinks.size() > 0) {
        // ensure there is a link to split
        linkIdx = nodeRand.nextInt(nodeLinks.size());
        chosen = (NEATLinkGene) nodeLinks.get(linkIdx);
        // disable old link
        chosen.setEnabled(false);
        newNode = InnovationDatabase.database().submitNodeInnovation(chosen);
        // newNode.setBias(MathUtils.nextPlusMinusOne());
        newLower =
            InnovationDatabase.database().submitLinkInnovation(chosen.getFromId(), newNode.id());
        newUpper =
            InnovationDatabase.database().submitLinkInnovation(newNode.id(), chosen.getToId());
        // set weights according to Stanley et al's NEAT document
        newLower.setWeight(1);
        newUpper.setWeight(chosen.getWeight());
        // now update the chromosome with new node and 2 new links
        newChromo[this.findChosenIndex(chosen, mutatee)] = newNode;
        // newChromo[newChromoIdx++] = newNode;
        newChromo[newChromoIdx++] = newLower;
        newChromo[newChromoIdx] = newUpper;
        mutatee.updateChromosome(newChromo);
      }
    }
  }
  private void mutateAddLink(Chromosome mutatee) {
    double linkRandVal = linkRand.nextDouble();
    NEATNodeGene from;
    NEATNodeGene to;
    int rIdx;
    int i = 0;
    ArrayList links;
    ArrayList nodes;
    Gene[] genes = new Gene[mutatee.size() + 1];
    System.arraycopy(mutatee.genes(), 0, genes, 0, mutatee.genes().length);
    Gene newLink = null;

    if (linkRandVal < this.pAddLink) {
      nodes = this.candidateNodes(mutatee.genes());
      links = this.candidateLinks(mutatee.genes(), false);
      // find a new available link
      while (newLink == null && i < MAX_LINK_ATTEMPTS) {
        rIdx = linkRand.nextInt(nodes.size());
        from = ((NEATNodeGene) nodes.get(rIdx));
        rIdx = linkRand.nextInt(nodes.size());
        to = ((NEATNodeGene) nodes.get(rIdx));
        // TODO Remove
        if (from.getInnovationNumber() == 2 && to.getInnovationNumber() == 5) {
          System.out.println("a");
        }
        if (!this.linkIllegal(from, to, links)) {
          // set it to a random value
          newLink = InnovationDatabase.database().submitLinkInnovation(from.id(), to.id());
          ((NEATLinkGene) newLink).setWeight(MathUtils.nextPlusMinusOne());
          // add link between 2 unconnected nodes
          genes[genes.length - 1] = newLink;
          mutatee.updateChromosome(genes);
        }
        i++;
      }
    }
  }