public double merge(
      int index1,
      int index2,
      int clusterIndex1,
      int clusterIndex2,
      int[] cluster1Sites,
      int[] cluster2Sites) {

    /*if(Math.abs(modelList.getParameter(clusterIndex1).getValue() - modelList.getParameter(clusterIndex2).getValue()) > 1.0){
        return Double.NEGATIVE_INFINITY;

    }*/

    double logqMerge = 0.0;

    HashMap<Integer, Integer> siteMap = new HashMap<Integer, Integer>();

    // The value of the merged cluster will have that of cluster 2 before the merge.
    QuietRealParameter mergedRates = ratesList.getParameter(clusterIndex2);
    QuietRealParameter mergedAlpha = alphaList.getParameter(clusterIndex2);
    QuietRealParameter mergedInvPr = invPrList.getParameter(clusterIndex2);
    QuietRealParameter mergedSiteModel = siteModelList.getParameter(clusterIndex2);

    // Create a vector that combines the site indices of the two clusters
    int[] mergedClusterSites = new int[cluster1Sites.length + cluster2Sites.length - 2];

    int k = 0;
    for (int i = 0; i < cluster1Sites.length; i++) {

      if (cluster1Sites[i] != index1) {
        // For all members that are not index 1,
        // record the cluster in which they have been before the merge,
        // and assign them to the combined vector.
        siteMap.put(cluster1Sites[i], clusterIndex1);
        mergedClusterSites[k++] = cluster1Sites[i];
      }
    }

    for (int i = 0; i < cluster2Sites.length; i++) {
      // All members in cluster 2 remains in cluster2 so no new pointer assignments
      if (cluster2Sites[i] != index2) {
        // For all members that are not index 2,
        // record the cluster in which they have been before the merge,
        // and assign them to the combined vector.
        siteMap.put(cluster2Sites[i], clusterIndex2);
        try {
          mergedClusterSites[k++] = cluster2Sites[i];
        } catch (Exception e) {
          System.out.println("k: " + k);
          System.out.println("i: " + i);
          System.out.println("cluster2Sites.length: " + cluster2Sites.length);
          System.out.println("index2: " + index2);
          for (int index : cluster2Sites) {
            System.out.print(index + " ");
          }
          System.out.println();
          throw new RuntimeException("");
        }
      }
    }

    try {

      // Create a weight vector of patterns to inform the temporary tree likelihood
      // which set of pattern likelihoods are to be computed.
      // int[] tempWeights = dpTreeLikelihood.getClusterWeights(clusterIndex1);
      /*int[] tempWeights = new int[tempLikelihood.m_data.get().getPatternCount()];
      for(int i = 0; i < cluster1Sites.length; i++){
          int patIndex = tempLikelihood.m_data.get().getPatternIndex(cluster1Sites[i]);
          tempWeights[patIndex] = 1;
      }
      tempLikelihood.setPatternWeights(tempWeights);
      double[] cluster1SitesCluster2ParamLogLik = tempLikelihood.calculateLogP(
              mergedParam,
              mergedModel,
              mergedFreqs,
              cluster1Sites,
              index1
      );*/

      k = 0;
      int[] sCluster1Sites = new int[cluster1Sites.length - 1];
      for (int i = 0; i < cluster1Sites.length; i++) {
        if (cluster1Sites[i] != index1) {
          sCluster1Sites[k++] = cluster1Sites[i];
        }
      }

      tempLikelihood.setupPatternWeightsFromSites(sCluster1Sites);
      double[] cluster1SitesCluster2ParamLogLik =
          tempLikelihood.calculateLogP(
              mergedAlpha.getValue(),
              mergedInvPr.getValue(),
              mergedRates.getValue(),
              mergedSiteModel.getValue(),
              sCluster1Sites);

      // tempWeights = dpTreeLikelihood.getClusterWeights(clusterIndex2);
      /*tempWeights = new int[tempLikelihood.m_data.get().getPatternCount()];
      for(int i = 0; i < cluster2Sites.length; i++){
          int patIndex = tempLikelihood.m_data.get().getPatternIndex(cluster2Sites[i]);
          tempWeights[patIndex] = 1;
      }
      tempLikelihood.setPatternWeights(tempWeights);
      QuietRealParameter removedParam = paramList.getParameter(clusterIndex1);
      QuietRealParameter removedModel = modelList.getParameter(clusterIndex1);
      QuietRealParameter removedFreqs = freqsList.getParameter(clusterIndex1);
      double[] cluster2SitesCluster1ParamLogLik = tempLikelihood.calculateLogP(
              removedParam,
              removedModel,
              removedFreqs,
              cluster2Sites,
              index2
      ); */

      k = 0;
      int[] sCluster2Sites = new int[cluster2Sites.length - 1];
      for (int i = 0; i < cluster2Sites.length; i++) {
        if (cluster2Sites[i] != index2) {
          sCluster2Sites[k++] = cluster2Sites[i];
        }
      }
      tempLikelihood.setupPatternWeightsFromSites(sCluster2Sites);
      QuietRealParameter removedAlpha = alphaList.getParameter(clusterIndex1);
      QuietRealParameter removedInvPr = invPrList.getParameter(clusterIndex1);
      QuietRealParameter removedRates = ratesList.getParameter(clusterIndex1);
      QuietRealParameter removedSiteModel = siteModelList.getParameter(clusterIndex1);
      double[] cluster2SitesCluster1ParamLogLik =
          tempLikelihood.calculateLogP(
              removedAlpha.getValue(),
              removedInvPr.getValue(),
              removedRates.getValue(),
              removedSiteModel.getValue(),
              sCluster2Sites);

      // System.out.println("populate logLik1:");
      double[] logLik1 = new double[mergedClusterSites.length];
      for (int i = 0; i < (cluster1Sites.length - 1); i++) {
        // System.out.println(clusterIndex1+" "+mergedClusterSites[i]);

        // logLik1[i] = dpTreeLikelihood.getSiteLogLikelihood(clusterIndex1,mergedClusterSites[i]);
        logLik1[i] =
            getSiteLogLikelihood(removedRates.getIDNumber(), clusterIndex1, mergedClusterSites[i]);
      }
      /*System.out.println(cluster2SitesCluster1ParamLogLik.length);
      System.out.println(logLik1.length);
      System.out.println(cluster1Sites.length-1);
      System.out.println(cluster2SitesCluster1ParamLogLik.length);*/
      System.arraycopy(
          cluster2SitesCluster1ParamLogLik,
          0,
          logLik1,
          cluster1Sites.length - 1,
          cluster2SitesCluster1ParamLogLik.length);

      double[] logLik2 = new double[mergedClusterSites.length];
      System.arraycopy(
          cluster1SitesCluster2ParamLogLik, 0, logLik2, 0, cluster1SitesCluster2ParamLogLik.length);

      // System.out.println("populate logLik2:");
      for (int i = cluster1SitesCluster2ParamLogLik.length; i < logLik2.length; i++) {
        // System.out.println(clusterIndex2+"
        // "+mergedClusterSites[i-cluster1SitesCluster2ParamLogLik.length]);
        // logLik2[i] = dpTreeLikelihood.getSiteLogLikelihood(clusterIndex2,mergedClusterSites[i]);
        logLik2[i] =
            getSiteLogLikelihood(mergedRates.getIDNumber(), clusterIndex2, mergedClusterSites[i]);
      }

      double[] lik1 = new double[logLik1.length];
      double[] lik2 = new double[logLik2.length];

      double maxLog;
      // scale it so it may be more accurate
      for (int i = 0; i < logLik1.length; i++) {
        maxLog = Math.max(logLik1[i], logLik2[i]);
        // System.out.println(i+" "+logLik1[i]+" "+logLik2[i]);
        if (Math.exp(maxLog) < 1e-100) {
          if (maxLog == logLik1[i]) {
            lik1[i] = 1.0;
            lik2[i] = Math.exp(logLik2[i] - maxLog);
            // System.out.println(i+" "+lik1[i]+" "+lik2[i]);
          } else {
            lik1[i] = Math.exp(logLik1[i] - maxLog);
            lik2[i] = 1.0;
            // System.out.println(i+" "+lik1[i]+" "+lik2[i]);
          }
        } else {

          lik1[i] = Math.exp(logLik1[i]);
          lik2[i] = Math.exp(logLik2[i]);
        }
      }

      /*for(int i = 0; i < logLik1.length; i++){
          if(Double.isNaN(logLik1[i])){
              //System.out.println("logLik1: "+logLik1[i]);
              return Double.NEGATIVE_INFINITY;

          }
          if(Double.isNaN(logLik2[i])){
              //System.out.println("logLik2: "+logLik2[i]);
              return Double.NEGATIVE_INFINITY;

          }
          lik1[i] = Math.exp(logLik1[i]);
          lik2[i] = Math.exp(logLik2[i]);
          //System.out.println(lik1[i]+" "+lik2[i]);
      }  */

      // Create a set of indices for random permutation
      int[] shuffle = new int[mergedClusterSites.length];
      for (int i = 0; i < shuffle.length; i++) {
        shuffle[i] = i;
      }
      Randomizer.shuffle(shuffle);

      int cluster1Count = 1;
      int cluster2Count = 1;
      int cluster;
      double psi1, psi2, cluster1Prob;
      for (int i = 0; i < mergedClusterSites.length; i++) {
        cluster = siteMap.get(mergedClusterSites[shuffle[i]]);
        psi1 = cluster1Count * lik1[shuffle[i]];
        psi2 = cluster2Count * lik2[shuffle[i]];
        // System.out.println(psi1+" "+psi2);

        if (testCorrect) {
          testCorrectness(
              i, cluster, clusterIndex1, clusterIndex2, shuffle, mergedClusterSites, lik1, lik2);
        }

        cluster1Prob = psi1 / (psi1 + psi2);
        if (cluster == clusterIndex1) {
          logqMerge += Math.log(cluster1Prob);
          cluster1Count++;

        } else if (cluster == clusterIndex2) {
          logqMerge += Math.log(1 - cluster1Prob);
          cluster2Count++;

        } else {
          throw new RuntimeException("Something is wrong.");
        }
      }

      logqMerge += // paramBaseDistr.calcLogP(removedParam)+
          mergeValueInLogSpace(removedRates, mergedRates, ratesBaseDistr)
              + mergeValueInLogSpace(removedAlpha, mergedAlpha, alphaBaseDistr)
              + mergeValue(removedInvPr, mergedInvPr, invPrBaseDistr)
              +
              // modelBaseDistr.calcLogP(removedModel)+
              mergeDiscreteValue(removedSiteModel, mergedSiteModel, siteModelBaseDistr);

      if (logqMerge > Double.NEGATIVE_INFINITY) {
        ratesList.mergeParameter(clusterIndex1, clusterIndex2);
        alphaList.mergeParameter(clusterIndex1, clusterIndex2);
        invPrList.mergeParameter(clusterIndex1, clusterIndex2);
        siteModelList.mergeParameter(clusterIndex1, clusterIndex2);
        for (int i = 0; i < cluster1Sites.length; i++) {
          // Point every member in cluster 1 to cluster 2
          ratesPointers.point(cluster1Sites[i], mergedRates);
        }
      }
    } catch (Exception e) {
      throw new RuntimeException(e);
    }

    return logqMerge;
  }