#include "Optimiser.h"

/****************************************************************************
  Create a new Optimiser object

  Be sure to call

  igraph_i_set_attribute_table(&igraph_cattribute_table);

  before using this package, otherwise the attribute handling
  will not be dealt with correctly.

  Parameters:
    consider_comms
                 -- Consider communities in a specific manner:
        ALL_COMMS       -- Consider all communities for improvement.
        ALL_NEIGH_COMMS -- Consider all neighbour communities for
                           improvement.
        RAND_COMM       -- Consider a random commmunity for improvement.
        RAND_NEIGH_COMM -- Consider a random community among the neighbours
                           for improvement.
****************************************************************************/
Optimiser::Optimiser()
{
  this->consider_comms = Optimiser::ALL_NEIGH_COMMS;
  this->optimise_routine = Optimiser::MOVE_NODES;
  this->refine_consider_comms = Optimiser::ALL_NEIGH_COMMS;
  this->refine_routine = Optimiser::MERGE_NODES;
  this->refine_partition = true;
  this->consider_empty_community = true;
  this->max_comm_size = 0;

  igraph_rng_init(&rng, &igraph_rngtype_mt19937);
  igraph_rng_seed(&rng, time(NULL));
}

Optimiser::~Optimiser()
{
  igraph_rng_destroy(&rng);
}

/*****************************************************************************
  optimise the provided partition.
*****************************************************************************/
double Optimiser::optimise_partition(MutableVertexPartition* partition)
{
 size_t n = partition->get_graph()->vcount();
 vector<bool> is_membership_fixed(n, false);
 return this->optimise_partition(partition, is_membership_fixed);
}

double Optimiser::optimise_partition(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed)
{
  return this->optimise_partition(partition, is_membership_fixed, this->max_comm_size);
}

double Optimiser::optimise_partition(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed, size_t max_comm_size)
{
  vector<MutableVertexPartition*> partitions(1);
  partitions[0] = partition;
  vector<double> layer_weights(1, 1.0);
  return this->optimise_partition(partitions, layer_weights, is_membership_fixed, max_comm_size);
}

double Optimiser::optimise_partition(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed)
{
  return this->optimise_partition(partitions, layer_weights, is_membership_fixed, this->max_comm_size);
}

/*****************************************************************************
  optimise the providede partitions simultaneously. We here use the sum
  of the difference of the moves as the overall quality function, each partition
  weighted by the layer weight.
*****************************************************************************/
/*****************************************************************************
  optimise the provided partition.
*****************************************************************************/
double Optimiser::optimise_partition(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, size_t max_comm_size)
{
  #ifdef DEBUG
    cerr << "void Optimiser::optimise_partition(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, size_t max_comm_size)" << endl;
  #endif

  double q = 0.0;

  // Number of multiplex layers
  size_t nb_layers = partitions.size();
  if (nb_layers == 0)
    throw Exception("No partitions provided.");

  // Get graphs for all layers
  vector<Graph*> graphs(nb_layers);
  for (size_t layer = 0; layer < nb_layers; layer++)
    graphs[layer] = partitions[layer]->get_graph();

  // Number of nodes in the graphs. Should be the same across
  // all graphs, so we only take the first one.
  size_t n = graphs[0]->vcount();

  // Make sure that all graphs contain the exact same number of nodes.
  // We assume the index of each vertex in the graph points to the
  // same node (but then in a different layer).
  for (Graph* graph : graphs)
    if (graph->vcount() != n)
      throw Exception("Number of nodes are not equal for all graphs.");

  // Get the fixed membership for fixed nodes
  vector<size_t> fixed_nodes;
  vector<size_t> fixed_membership(n);
  for (size_t v = 0; v < n; v++) {
    if (is_membership_fixed[v]) {
      fixed_nodes.push_back(v);
      fixed_membership[v] = partitions[0]->membership(v);
    }
  }

  // Initialize the vector of the collapsed graphs for all layers
  vector<Graph*> collapsed_graphs(nb_layers);
  vector<MutableVertexPartition*> collapsed_partitions(nb_layers);

  // Declare the collapsed_graph variable which will contain the graph
  // collapsed by its communities. We will use this variables at each
  // further iteration, so we don't keep a collapsed graph at each pass.
  for (size_t layer = 0; layer < nb_layers; layer++)
  {
    collapsed_graphs[layer] = graphs[layer];
    collapsed_partitions[layer] = partitions[layer];
  }

  // Declare which nodes in the collapsed graph are fixed, which to start is
  // simply equal to is_membership_fixed
  vector<bool> is_collapsed_membership_fixed(is_membership_fixed);

  // This reflects the aggregate node, which to start with is simply equal to the graph.
  vector<size_t> aggregate_node_per_individual_node = range(n);
  bool aggregate_further = true;
  // As long as there remains improvement iterate
  double improv = 0.0;
  do
  {

    // Optimise partition for collapsed graph
    #ifdef DEBUG
      q = 0.0;
      for (size_t layer = 0; layer < nb_layers; layer++)
        q += partitions[layer]->quality()*layer_weights[layer];
      cerr << "Quality before moving " <<  q << endl;
    #endif
    if (this->optimise_routine == Optimiser::MOVE_NODES)
      improv += this->move_nodes(collapsed_partitions, layer_weights, is_collapsed_membership_fixed, this->consider_comms, this->consider_empty_community, false, max_comm_size);

    else if (this->optimise_routine == Optimiser::MERGE_NODES)
      improv += this->merge_nodes(collapsed_partitions, layer_weights, is_collapsed_membership_fixed, this->consider_comms, false, max_comm_size);

    #ifdef DEBUG
      cerr << "Found " << collapsed_partitions[0]->n_communities() << " communities, improved " << improv << endl;
      q = 0.0;
      for (size_t layer = 0; layer < nb_layers; layer++)
        q += partitions[layer]->quality()*layer_weights[layer];
      cerr << "Quality after moving " <<  q << endl;
    #endif // DEBUG

    // Make sure improvement on coarser scale is reflected on the
    // scale of the graph as a whole.
    for (size_t layer = 0; layer < nb_layers; layer++)
    {
      if (collapsed_partitions[layer] != partitions[layer])
      {
        if (this->refine_partition)
          partitions[layer]->from_coarse_partition(collapsed_partitions[layer], aggregate_node_per_individual_node);
        else
          partitions[layer]->from_coarse_partition(collapsed_partitions[layer]);
      }
    }

    #ifdef DEBUG
      q = 0.0;
      for (size_t layer = 0; layer < nb_layers; layer++)
        q += partitions[layer]->quality()*layer_weights[layer];
      cerr << "Quality on finer partition " << q << endl;
    #endif // DEBUG

    #ifdef DEBUG
        cerr << "Number of communities: " << partitions[0]->n_communities() << endl;
    #endif

    // Collapse graph (i.e. community graph)
    // If we do refine the partition, we separate communities in slightly more
    // fine-grained parts for which we collapse the graph.
    vector<MutableVertexPartition*> sub_collapsed_partitions(nb_layers);

    vector<Graph*> new_collapsed_graphs(nb_layers);
    vector<MutableVertexPartition*> new_collapsed_partitions(nb_layers);

    if (this->refine_partition)
    {
      // First create a new partition, which should be a sub partition
      // of the collapsed partition, i.e. such that all clusters of
      // the partition are strictly partitioned in the subpartition.

      #ifdef DEBUG
        cerr << "\tBefore SLM " << collapsed_partitions[0]->n_communities() << " communities." << endl;
      #endif
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        sub_collapsed_partitions[layer] = collapsed_partitions[layer]->create(collapsed_graphs[layer]);
      }

      // Then move around nodes but restrict movement to within original communities.
      #ifdef DEBUG
        cerr << "\tStarting refinement with " << sub_collapsed_partitions[0]->n_communities() << " communities." << endl;
      #endif
      if (this->refine_routine == Optimiser::MOVE_NODES)
        this->move_nodes_constrained(sub_collapsed_partitions, layer_weights, refine_consider_comms, collapsed_partitions[0], max_comm_size);
      else if (this->refine_routine == Optimiser::MERGE_NODES)
        this->merge_nodes_constrained(sub_collapsed_partitions, layer_weights, refine_consider_comms, collapsed_partitions[0], max_comm_size);
      #ifdef DEBUG
        cerr << "\tAfter applying refinement found " << sub_collapsed_partitions[0]->n_communities() << " communities." << endl;
      #endif

      // Determine new aggregate node per individual node
      for (size_t v = 0; v < n; v++)
      {
        size_t aggregate_node = aggregate_node_per_individual_node[v];
        aggregate_node_per_individual_node[v] = sub_collapsed_partitions[0]->membership(aggregate_node);
      }

      // Collapse graph based on sub collapsed partition
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        new_collapsed_graphs[layer] = collapsed_graphs[layer]->collapse_graph(sub_collapsed_partitions[layer]);
      }

      // Determine the membership for the collapsed graph
      vector<size_t> new_collapsed_membership(new_collapsed_graphs[0]->vcount());

      // Every node within the collapsed graph should be assigned
      // to the community of the original partition before the refinement.
      // We thus check for each node what the community is in the refined partition
      // and set the membership equal to the original partition (i.e.
      // even though the aggregation may be slightly different, the
      // membership of the aggregated nodes is as indicated by the original partition.)
      #ifdef DEBUG
        //cerr << "Refinement\tOrig" << endl;
      #endif // DEBUG
      for (size_t v = 0; v < collapsed_graphs[0]->vcount(); v++)
      {
        size_t new_aggregate_node = sub_collapsed_partitions[0]->membership(v);
        new_collapsed_membership[new_aggregate_node] = collapsed_partitions[0]->membership(v);
        #ifdef DEBUG
          //cerr << sub_collapsed_partition->membership(v) << "\t" << sub_collapsed_partition->membership(v) << endl;
        #endif // DEBUG
      }

      // Determine which collapsed nodes are fixed
      is_collapsed_membership_fixed.clear();
      is_collapsed_membership_fixed.resize(new_collapsed_graphs[0]->vcount(), false);
      for (size_t v = 0; v < n; v++)
        if (is_membership_fixed[v])
          is_collapsed_membership_fixed[aggregate_node_per_individual_node[v]] = true;

      // Create new collapsed partition
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        delete sub_collapsed_partitions[layer];
        new_collapsed_partitions[layer] = collapsed_partitions[layer]->create(new_collapsed_graphs[layer], new_collapsed_membership);
      }
    }
    else
    {
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        new_collapsed_graphs[layer] = collapsed_graphs[layer]->collapse_graph(collapsed_partitions[layer]);
        // Create collapsed partition (i.e. default partition of each node in its own community).
        new_collapsed_partitions[layer] = collapsed_partitions[layer]->create(new_collapsed_graphs[layer]);
        #ifdef DEBUG
          cerr << "Layer " << layer << endl;
          cerr << "Old collapsed graph " << collapsed_graphs[layer] << ", vcount is " << collapsed_graphs[layer]->vcount() << endl;
          cerr << "New collapsed graph " << new_collapsed_graphs[layer] << ", vcount is " << new_collapsed_graphs[layer]->vcount() << endl;
        #endif
      }
    }

    // Determine whether to aggregate further
    // If all is fixed, no need to aggregate
    aggregate_further = false;
    for (const bool& membership_fixed : is_collapsed_membership_fixed)
    {
      if(!membership_fixed) {
        aggregate_further = true;
        break;
      }
    }
    // else, check whether anything has stirred since last time
    aggregate_further &= (new_collapsed_graphs[0]->vcount() < collapsed_graphs[0]->vcount()) &&
                         (collapsed_graphs[0]->vcount() > collapsed_partitions[0]->n_communities());

    #ifdef DEBUG
      cerr << "Aggregate further " << aggregate_further << endl;
    #endif

    // Delete the previous collapsed partition and graph
    for (size_t layer = 0; layer < nb_layers; layer++)
    {
      if (collapsed_partitions[layer] != partitions[layer])
        delete collapsed_partitions[layer];
      if (collapsed_graphs[layer] != graphs[layer])
        delete collapsed_graphs[layer];
    }

    // and set them to the new one.
    collapsed_partitions = new_collapsed_partitions;
    collapsed_graphs = new_collapsed_graphs;

    #ifdef DEBUG
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        cerr <<   "Calculate partition " << layer  << " quality." << endl;
        q = partitions[layer]->quality()*layer_weights[layer];
        cerr <<   "Calculate collapsed partition quality." << endl;
        double q_collapsed = 0.0;
        q_collapsed += collapsed_partitions[layer]->quality()*layer_weights[layer];
        if (fabs(q - q_collapsed) > 1e-6)
        {
          cerr << "ERROR: Quality of original partition and collapsed partition are not equal." << endl;
        }
        cerr <<   "partition->quality()=" << q
             << ", collapsed_partition->quality()=" << q_collapsed << endl;
        cerr <<   "graph->total_weight()=" << graphs[layer]->total_weight()
             << ", collapsed_graph->total_weight()=" << collapsed_graphs[layer]->total_weight() << endl;
        cerr <<   "graph->vcount()=" << graphs[layer]->vcount()
             << ", collapsed_graph->vcount()="  << collapsed_graphs[layer]->vcount() << endl;
        cerr <<   "graph->ecount()=" << graphs[layer]->ecount()
             << ", collapsed_graph->ecount()="  << collapsed_graphs[layer]->ecount() << endl;
        cerr <<   "graph->is_directed()=" << graphs[layer]->is_directed()
             << ", collapsed_graph->is_directed()="  << collapsed_graphs[layer]->is_directed() << endl;
        cerr <<   "graph->correct_self_loops()=" << graphs[layer]->correct_self_loops()
             << ", collapsed_graph->correct_self_loops()="  << collapsed_graphs[layer]->correct_self_loops() << endl << endl;
      }
    #endif // DEBUG

  } while (aggregate_further);

  // Clean up memory after use.
  for (size_t layer = 0; layer < nb_layers; layer++)
  {
    if (collapsed_partitions[layer] != partitions[layer])
      delete collapsed_partitions[layer];

    if (collapsed_graphs[layer] != graphs[layer])
      delete collapsed_graphs[layer];
  }

  // Make sure the resulting communities are called 0,...,r-1
  // where r is the number of communities. The exception is fixed
  // nodes which should keep the numbers of the original communities
  q = 0.0;
  partitions[0]->renumber_communities();
  partitions[0]->renumber_communities(fixed_nodes, fixed_membership);
  vector<size_t> const& membership = partitions[0]->membership();
  // We only renumber the communities for the first graph,
  // since the communities for the other graphs should just be equal
  // to the membership of the first graph.
  for (size_t layer = 1; layer < nb_layers; layer++)
  {
    partitions[layer]->set_membership(membership);
    q += partitions[layer]->quality()*layer_weights[layer];
  }
  return improv;
}

/*****************************************************************************
    Move nodes to other communities depending on how other communities are
    considered, see consider_comms parameter of the class.

    Parameters:
      partition -- The partition to optimise.
******************************************************************************/
double Optimiser::move_nodes(MutableVertexPartition* partition)
{
  return this->move_nodes(partition, this->consider_comms);
}

double Optimiser::move_nodes(MutableVertexPartition* partition, int consider_comms)
{
  vector<bool> is_membership_fixed(partition->get_graph()->vcount());
  return this->move_nodes(partition, is_membership_fixed, consider_comms, false);
}

double Optimiser::move_nodes(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes)
{
  return this->move_nodes(partition, is_membership_fixed, consider_comms, renumber_fixed_nodes, this->max_comm_size);
}

double Optimiser::move_nodes(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes, size_t max_comm_size)
{
  vector<MutableVertexPartition*> partitions(1);
  partitions[0] = partition;
  vector<double> layer_weights(1, 1.0);
  return this->move_nodes(partitions, layer_weights, is_membership_fixed, consider_comms, this->consider_empty_community, renumber_fixed_nodes, max_comm_size);
}

double Optimiser::merge_nodes(MutableVertexPartition* partition)
{
  return this->merge_nodes(partition, this->consider_comms);
}

double Optimiser::merge_nodes(MutableVertexPartition* partition, int consider_comms)
{
  vector<bool> is_membership_fixed(partition->get_graph()->vcount());
  return this->merge_nodes(partition, is_membership_fixed, consider_comms, false);
}

double Optimiser::merge_nodes(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes)
{
  return this->merge_nodes(partition, is_membership_fixed, consider_comms, renumber_fixed_nodes, this->max_comm_size);
}

double Optimiser::merge_nodes(MutableVertexPartition* partition, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes, size_t max_comm_size)
{
  vector<MutableVertexPartition*> partitions(1);
  partitions[0] = partition;
  vector<double> layer_weights(1, 1.0);
  return this->merge_nodes(partitions, layer_weights, is_membership_fixed, consider_comms, renumber_fixed_nodes, max_comm_size);
}

double Optimiser::move_nodes_constrained(MutableVertexPartition* partition, MutableVertexPartition* constrained_partition)
{
  return this->move_nodes_constrained(partition, this->refine_consider_comms, constrained_partition);
}

double Optimiser::move_nodes_constrained(MutableVertexPartition* partition, int consider_comms, MutableVertexPartition* constrained_partition)
{
  return this->move_nodes_constrained(partition, consider_comms, constrained_partition, this->max_comm_size);
}

double Optimiser::move_nodes_constrained(MutableVertexPartition* partition, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)
{
  vector<MutableVertexPartition*> partitions(1);
  partitions[0] = partition;
  vector<double> layer_weights(1, 1.0);
  return this->move_nodes_constrained(partitions, layer_weights, consider_comms, constrained_partition, max_comm_size);
}

double Optimiser::merge_nodes_constrained(MutableVertexPartition* partition, MutableVertexPartition* constrained_partition)
{
  return this->merge_nodes_constrained(partition, this->refine_consider_comms, constrained_partition);
}

double Optimiser::merge_nodes_constrained(MutableVertexPartition* partition, int consider_comms, MutableVertexPartition* constrained_partition)
{
  return this->merge_nodes_constrained(partition, consider_comms, constrained_partition, this->max_comm_size);
}

double Optimiser::merge_nodes_constrained(MutableVertexPartition* partition, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)
{
  vector<MutableVertexPartition*> partitions(1);
  partitions[0] = partition;
  vector<double> layer_weights(1, 1.0);
  return this->merge_nodes_constrained(partitions, layer_weights, consider_comms, constrained_partition, max_comm_size);
}

/*****************************************************************************
  Move nodes to neighbouring communities such that each move improves the
  given quality function maximally (i.e. greedily) for multiple layers,
  i.e. for multiplex networks. Each node will be in the same community in
  each layer, but the method may be different, or the weighting may be
  different for different layers. Notably, this can be used in the case of
  negative links, where you would like to weigh the negative links with a
  negative weight.

  Parameters:
    partitions -- The partitions to optimise.
    layer_weights -- The weights used for the different layers.
******************************************************************************/
double Optimiser::move_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, bool renumber_fixed_nodes)
{
  return this->move_nodes(partitions, layer_weights, is_membership_fixed, this->consider_comms, this->consider_empty_community, renumber_fixed_nodes);
}

double Optimiser::move_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, int consider_empty_community)
{
  return this->move_nodes(partitions, layer_weights, is_membership_fixed, consider_comms, consider_empty_community, true);
}

double Optimiser::move_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, int consider_empty_community, bool renumber_fixed_nodes)
{
    return this->move_nodes(partitions, layer_weights, is_membership_fixed, consider_comms, consider_empty_community, renumber_fixed_nodes, this->max_comm_size);
}

double Optimiser::move_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, int consider_empty_community, bool renumber_fixed_nodes, size_t max_comm_size)
{
  #ifdef DEBUG
    cerr << "double Optimiser::move_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, int consider_empty_community, bool renumber_fixed_nodes, size_t max_comm_size)" << endl;
  #endif
  // Number of multiplex layers
  size_t nb_layers = partitions.size();
  if (nb_layers == 0)
    return -1.0;
  // Get graphs
  vector<Graph*> graphs(nb_layers);
  for (size_t layer = 0; layer < nb_layers; layer++)
    graphs[layer] = partitions[layer]->get_graph();
  // Number of nodes in the graph
  size_t n = graphs[0]->vcount();

  // Get the fixed membership for fixed nodes
  vector<size_t> fixed_nodes;
  vector<size_t> fixed_membership(n);
  if (renumber_fixed_nodes) {
    for (size_t v = 0; v < n; v++) {
      if (is_membership_fixed[v]) {
        fixed_nodes.push_back(v);
        fixed_membership[v] = partitions[0]->membership(v);
      }
    }
  }

  // Total improvement while moving nodes
  double total_improv = 0.0;

  for (Graph* graph : graphs)
    if (graph->vcount() != n)
      throw Exception("Number of nodes are not equal for all graphs.");
  // Number of moved nodes during one loop
  size_t nb_moves = 0;

  // Fixed nodes are also stable nodes
  vector<bool> is_node_stable(is_membership_fixed);

  // Establish vertex order
  // We normally initialize the normal vertex order
  // of considering node 0,1,...
  // But if we use a random order, we shuffle this order.
  // Also, we skip fixed nodes from the queue for efficiency reasons
  vector<size_t> nodes;
  for (size_t v = 0; v != is_membership_fixed.size(); v++) {
    if (!is_membership_fixed[v])
      nodes.push_back(v);
  }
  shuffle(nodes, &rng);
  deque<size_t> vertex_order(nodes.begin(), nodes.end());

  // Initialize the degree vector
  // If we want to debug the function, we will calculate some additional values.
  // In particular, the following consistencies could be checked:
  // (1) - The difference in the quality function after a move should match
  //       the reported difference when calling diff_move.
  // (2) - The quality function should be exactly the same value after
  //       aggregating/collapsing the graph.

  vector<bool> comm_added(partitions[0]->n_communities(), false);
  vector<size_t> comms;

  // As long as the queue is not empty
  while(!vertex_order.empty())
  {
    size_t v = vertex_order.front(); vertex_order.pop_front();

    // What is the current community of the node (this should be the same for all layers)
    size_t v_comm = partitions[0]->membership(v);

    if (consider_comms == ALL_COMMS)
    {
      for(size_t comm = 0; comm < partitions[0]->n_communities(); comm++)
      {
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          if (partitions[layer]->cnodes(comm) > 0 && !comm_added[comm])
          {
            comms.push_back(comm);
            comm_added[comm] = true;
            break; // Break from for loop in layer
          }
        }

      }
    }
    else if (consider_comms == ALL_NEIGH_COMMS)
    {
      /****************************ALL NEIGH COMMS*****************************/
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        for (size_t comm : partitions[layer]->get_neigh_comms(v, IGRAPH_ALL))
        {
          if (!comm_added[comm])
          {
              comms.push_back(comm);
              comm_added[comm] = true;
          }
        }
      }
    }
    else if (consider_comms == RAND_COMM)
    {
      /****************************RAND COMM***********************************/
      size_t rand_comm = partitions[0]->membership(graphs[0]->get_random_node(&rng));
      // No need to check if random_comm is already added, we only add one comm
      comms.push_back(rand_comm);
      comm_added[rand_comm] = true;
    }
    else if (consider_comms == RAND_NEIGH_COMM)
    {
      /****************************RAND NEIGH COMM*****************************/
      size_t rand_layer = get_random_int(0, nb_layers - 1, &rng);
      if (graphs[rand_layer]->degree(v, IGRAPH_ALL) > 0)
      {
        size_t rand_comm = partitions[0]->membership(graphs[rand_layer]->get_random_neighbour(v, IGRAPH_ALL, &rng));
        // No need to check if random_comm is already added, we only add one comm
        comms.push_back(rand_comm);
        comm_added[rand_comm] = true;
      }
    }

    // Check if we should move to an empty community
    if (consider_empty_community)
    {
      if ( partitions[0]->cnodes(v_comm) > 1 )  // We should not move a node when it is already in its own empty community (this may otherwise create more empty communities than nodes)
      {
        size_t n_comms = partitions[0]->n_communities();
        size_t comm = partitions[0]->get_empty_community();
        #ifdef DEBUG
          cerr << "Checking empty community (" << comm << ") for partition " << partitions[0] << endl;
        #endif
        comms.push_back(comm);
        if (partitions[0]->n_communities() > n_comms)
        {
          // If the empty community has just been added, we need to make sure
          // that is has also been added to the other layers
          for (size_t layer = 1; layer < nb_layers; layer++)
              partitions[layer]->add_empty_community();
          comm_added.push_back(true);
        }
      }
    }

    #ifdef DEBUG
      cerr << "Consider " << comms.size() << " communities for moving." << endl;
    #endif

    size_t max_comm = v_comm;
    double max_improv = (0 < max_comm_size && max_comm_size < partitions[0]->csize(v_comm)) ? -INFINITY : 10*DBL_EPSILON;
    size_t v_size = graphs[0]->node_size(v);
    for (size_t comm : comms)
    {
      // reset comm_added to all false
      comm_added[comm] = false;

      // Do not create too-large communities.
      if (0 < max_comm_size && max_comm_size < partitions[0]->csize(comm) + v_size) {
        continue;
      }

      double possible_improv = 0.0;

      // Consider the improvement of moving to a community for all layers
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        // Make sure to multiply it by the weight per layer
        possible_improv += layer_weights[layer]*partitions[layer]->diff_move(v, comm);
      }

      if (possible_improv > max_improv)
      {
        max_comm = comm;
        max_improv = possible_improv;
      }
    }

    // Clear comms
    comms.clear();

    is_node_stable[v] = true;

    // If we actually plan to move the node
    if (max_comm != v_comm)
    {
        // Keep track of improvement
        total_improv += max_improv;

        #ifdef DEBUG
          // If we are debugging, calculate quality function
          double q_improv = 0;
        #endif

        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          MutableVertexPartition* partition = partitions[layer];

          #ifdef DEBUG
            // If we are debugging, calculate quality function
            double q1 = partition->quality();
          #endif

          // Actually move the node
          partition->move_node(v, max_comm);
          #ifdef DEBUG
            // If we are debugging, calculate quality function
            // and report difference
            double q2 = partition->quality();
            double q_delta = layer_weights[layer]*(q2 - q1);
            q_improv += q_delta;
            cerr << "Move node " << v
            << " from " << v_comm << " to " << max_comm << " for layer " << layer
            << " (diff_move=" << max_improv
            << ", q2 - q1=" << q_delta << ")" << endl;
          #endif
        }
        #ifdef DEBUG
          if (fabs(q_improv - max_improv) > 1e-6)
          {
            cerr << "ERROR: Inconsistency while moving nodes, improvement as measured by quality function did not equal the improvement measured by the diff_move function." << endl
                 << " (diff_move=" << max_improv
                 << ", q2 - q1=" << q_improv << ")" << endl;
          }
        #endif

        // Mark neighbours as unstable (if not in new community and not fixed)
        for (Graph* graph : graphs)
        {
          for (size_t u : graph->get_neighbours(v, IGRAPH_ALL))
          {
            // If the neighbour was stable and is not in the new community, we
            // should mark it as unstable, and add it to the queue, skipping
            // fixed nodes
            if (is_node_stable[u] && partitions[0]->membership(u) != max_comm && !is_membership_fixed[u])
            {
              vertex_order.push_back(u);
              is_node_stable[u] = false;
            }
          }
        }
        // Keep track of number of moves
        nb_moves += 1;
      }
  }

  partitions[0]->renumber_communities();
  if (renumber_fixed_nodes)
    partitions[0]->renumber_communities(fixed_nodes, fixed_membership);
  vector<size_t> const& membership = partitions[0]->membership();
  for (size_t layer = 1; layer < nb_layers; layer++)
  {
    partitions[layer]->set_membership(membership);
    #ifdef DEBUG
      cerr << "Renumbered communities for layer " << layer << " for " << partitions[layer]->n_communities() << " communities." << endl;
    #endif //DEBUG
  }
  return total_improv;
}

double Optimiser::merge_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, bool renumber_fixed_nodes)
{
  return this->merge_nodes(partitions, layer_weights, is_membership_fixed, this->consider_comms, renumber_fixed_nodes);
}

double Optimiser::merge_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes)
{
  return this->merge_nodes(partitions, layer_weights, is_membership_fixed, consider_comms, renumber_fixed_nodes, this->max_comm_size);
}

double Optimiser::merge_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes, size_t max_comm_size)
{
  #ifdef DEBUG
    cerr << "double Optimiser::merge_nodes(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, vector<bool> const& is_membership_fixed, int consider_comms, bool renumber_fixed_nodes, size_t max_comm)" << std::endl;
  #endif

  // Number of multiplex layers
  size_t nb_layers = partitions.size();
  if (nb_layers == 0)
    return -1.0;

  // Get graphs
  vector<Graph*> graphs(nb_layers);
  for (size_t layer = 0; layer < nb_layers; layer++)
    graphs[layer] = partitions[layer]->get_graph();
  // Number of nodes in the graph
  size_t n = graphs[0]->vcount();

  // Get the fixed membership for fixed nodes
  vector<size_t> fixed_nodes;
  vector<size_t> fixed_membership(n);
  if (renumber_fixed_nodes) {
    for (size_t v = 0; v < n; v++) {
      if (is_membership_fixed[v]) {
        fixed_nodes.push_back(v);
        fixed_membership[v] = partitions[0]->membership(v);
      }
    }
  }

  // Total improvement while merging nodes
  double total_improv = 0.0;

  for (Graph* graph : graphs)
    if (graph->vcount() != n)
      throw Exception("Number of nodes are not equal for all graphs.");

  // Establish vertex order, skipping fixed nodes
  // We normally initialize the normal vertex order
  // of considering node 0,1,...
  vector<size_t> vertex_order;
  for (size_t v = 0; v != n; v++)
    if (!is_membership_fixed[v])
      vertex_order.push_back(v);

  // But if we use a random order, we shuffle this order.
  shuffle(vertex_order, &rng);

  vector<bool> comm_added(partitions[0]->n_communities(), false);
  vector<size_t> comms;

  // Iterate over all nodes
  for (size_t v : vertex_order)
  {
    // What is the current community of the node (this should be the same for all layers)
    size_t v_comm = partitions[0]->membership(v);
    // Clear comms
    for (size_t comm : comms)
      comm_added[comm] = false;
    comms.clear();

    #ifdef DEBUG
      cerr << "Consider moving node " << v << " from " << v_comm << "." << endl;
    #endif

    if (partitions[0]->cnodes(v_comm) == 1)
    {
      if (consider_comms == ALL_COMMS)
      {
        for(size_t comm = 0; comm < partitions[0]->n_communities(); comm++)
        {
          for (size_t layer = 0; layer < nb_layers; layer++)
          {
            if (partitions[layer]->cnodes(comm) > 0 && !comm_added[comm])
            {
              comms.push_back(comm);
              comm_added[comm] = true;
              break; // Break from for loop in layer
            }
          }

        }
      }
      else if (consider_comms == ALL_NEIGH_COMMS)
      {
        /****************************ALL NEIGH COMMS*****************************/
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          for (size_t comm : partitions[layer]->get_neigh_comms(v, IGRAPH_ALL))
          {
            if (!comm_added[comm])
            {
                comms.push_back(comm);
                comm_added[comm] = true;
            }
          }
        }
      }
      else if (consider_comms == RAND_COMM)
      {
        /****************************RAND COMM***********************************/
        size_t rand_comm = partitions[0]->membership(graphs[0]->get_random_node(&rng));
        // No need to check if random_comm is already added, we only add one comm
        comms.push_back(rand_comm);
        comm_added[rand_comm] = true;
      }
      else if (consider_comms == RAND_NEIGH_COMM)
      {
        /****************************RAND NEIGH COMM*****************************/
        size_t rand_layer = get_random_int(0, nb_layers - 1, &rng);
        size_t k = graphs[rand_layer]->degree(v, IGRAPH_ALL);
        if (k > 0)
        {
          // Make sure there is also a probability not to move the node
          if (get_random_int(0, k, &rng) > 0)
          {
            size_t rand_comm = partitions[0]->membership(graphs[rand_layer]->get_random_neighbour(v, IGRAPH_ALL, &rng));
            // No need to check if random_comm is already added, we only add one comm
            comms.push_back(rand_comm);
            comm_added[rand_comm] = true;
          }
        }
      }

      #ifdef DEBUG
        cerr << "Consider " << comms.size() << " communities for moving node " << v << "." << endl;
      #endif

      size_t max_comm = v_comm;
      double max_improv = (0 < max_comm_size && max_comm_size < partitions[0]->csize(v_comm)) ? -INFINITY : 0;
      size_t v_size = graphs[0]->node_size(v);
      for (size_t comm : comms)
      {
        // Do not create too-large communities.
        if (0 < max_comm_size && max_comm_size < partitions[0]->csize(comm) + v_size) {
          continue;
        }

        double possible_improv = 0.0;

        // Consider the improvement of moving to a community for all layers
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          // Make sure to multiply it by the weight per layer
          possible_improv += layer_weights[layer]*partitions[layer]->diff_move(v, comm);
        }
        #ifdef DEBUG
          cerr << "Improvement of " << possible_improv << " when move to " << comm << "." << endl;
        #endif

        if (possible_improv >= max_improv)
        {
          max_comm = comm;
          max_improv = possible_improv;
        }
      }

      // If we actually plan to move the node
      if (max_comm != v_comm)
      {
          // Keep track of improvement
          total_improv += max_improv;

          #ifdef DEBUG
            // If we are debugging, calculate quality function
            double q_improv = 0;
          #endif

          for (size_t layer = 0; layer < nb_layers; layer++)
          {
            MutableVertexPartition* partition = partitions[layer];

            #ifdef DEBUG
              // If we are debugging, calculate quality function
              double q1 = partition->quality();
            #endif

            // Actually move the node
            partition->move_node(v, max_comm);
            #ifdef DEBUG
              // If we are debugging, calculate quality function
              // and report difference
              double q2 = partition->quality();
              double q_delta = layer_weights[layer]*(q2 - q1);
              q_improv += q_delta;
              cerr << "Move node " << v
              << " from " << v_comm << " to " << max_comm << " for layer " << layer
              << " (diff_move=" << max_improv
              << ", q2 - q1=" << q_delta << ")" << endl;
            #endif
          }
          #ifdef DEBUG
            if (fabs(q_improv - max_improv) > 1e-6)
            {
              cerr << "ERROR: Inconsistency while moving nodes, improvement as measured by quality function did not equal the improvement measured by the diff_move function." << endl
                   << " (diff_move=" << max_improv
                   << ", q2 - q1=" << q_improv << ")" << endl;
            }
          #endif
        }
      }
  }

  partitions[0]->renumber_communities();
  if (renumber_fixed_nodes)
    partitions[0]->renumber_communities(fixed_nodes, fixed_membership);
  vector<size_t> const& membership = partitions[0]->membership();
  for (size_t layer = 1; layer < nb_layers; layer++)
  {
    partitions[layer]->set_membership(membership);
    #ifdef DEBUG
      cerr << "Renumbered communities for layer " << layer << " for " << partitions[layer]->n_communities() << " communities." << endl;
    #endif //DEBUG
  }
  return total_improv;
}

double Optimiser::move_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, MutableVertexPartition* constrained_partition)
{
  return this->move_nodes_constrained(partitions, layer_weights, this->refine_consider_comms, constrained_partition);
}

double Optimiser::move_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition)
{
  return this->move_nodes_constrained(partitions, layer_weights, refine_consider_comms, constrained_partition, this->max_comm_size);
}

double Optimiser::move_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)
{
  #ifdef DEBUG
    cerr << "double Optimiser::move_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)" << std::endl;
  #endif
  // Number of multiplex layers
  size_t nb_layers = partitions.size();
  if (nb_layers == 0)
    return -1.0;
  // Get graphs
  vector<Graph*> graphs(nb_layers);
  for (size_t layer = 0; layer < nb_layers; layer++)
    graphs[layer] = partitions[layer]->get_graph();
  // Number of nodes in the graph
  size_t n = graphs[0]->vcount();

  // Total improvement while moving nodes
  double total_improv = 0.0;

  for (size_t layer = 0; layer < nb_layers; layer++)
    if (graphs[layer]->vcount() != n)
      throw Exception("Number of nodes are not equal for all graphs.");
  // Number of moved nodes during one loop
  size_t nb_moves = 0;

  // Establish vertex order
  // We normally initialize the normal vertex order
  // of considering node 0,1,...
  vector<bool> is_node_stable(n, false);
  // But if we use a random order, we shuffle this order.
  vector<size_t> nodes = range(n);
  shuffle(nodes, &rng);
  deque<size_t> vertex_order(nodes.begin(), nodes.end());

  vector< vector<size_t> > constrained_comms = constrained_partition->get_communities();

  // Initialize the degree vector
  // If we want to debug the function, we will calculate some additional values.
  // In particular, the following consistencies could be checked:
  // (1) - The difference in the quality function after a move should match
  //       the reported difference when calling diff_move.
  // (2) - The quality function should be exactly the same value after
  //       aggregating/collapsing the graph.

  vector<bool> comm_added(partitions[0]->n_communities(), false);
  vector<size_t> comms;

  // As long as the queue is not empty
  while(!vertex_order.empty())
  {
    size_t v = vertex_order.front(); vertex_order.pop_front();

    // Clear comms
    for (size_t comm : comms)
      comm_added[comm] = false;
    comms.clear();

    // What is the current community of the node (this should be the same for all layers)
    size_t v_comm = partitions[0]->membership(v);

    if (consider_comms == ALL_COMMS)
    {
        // Add all communities to the set comms that are within the constrained community.
        size_t v_constrained_comm = constrained_partition->membership(v);
        for (size_t u : constrained_comms[v_constrained_comm])
        {
          size_t u_comm = partitions[0]->membership(u);
          if (!comm_added[u_comm])
          {
            comms.push_back(u_comm);
            comm_added[u_comm] = true;
          }
        }
    }
    else if (consider_comms == ALL_NEIGH_COMMS)
    {
        /****************************ALL NEIGH COMMS*****************************/
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          for (size_t comm : partitions[layer]->get_neigh_comms(v, IGRAPH_ALL, constrained_partition->membership()))
          {
            if (!comm_added[comm])
            {
                comms.push_back(comm);
                comm_added[comm] = true;
            }
          }
        }
    }
    else if (consider_comms == RAND_COMM)
    {
      /****************************RAND COMM***********************************/
        size_t v_constrained_comm = constrained_partition->membership(v);
        size_t random_idx = get_random_int(0, constrained_comms[v_constrained_comm].size() - 1, &rng);
        size_t rand_comm = constrained_comms[v_constrained_comm][random_idx];
        // No need to check if random_comm is already added, we only add one comm
        comms.push_back(rand_comm);
        comm_added[rand_comm] = true;
    }
    else if (consider_comms == RAND_NEIGH_COMM)
    {
      /****************************RAND NEIGH COMM*****************************/
        // Draw a random community among the neighbours, proportional to the
        // frequency of the communities among the neighbours. Notice this is no
        // longer
        vector<size_t> all_neigh_comms_incl_dupes;
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          vector<size_t> neigh_comm_layer = partitions[layer]->get_neigh_comms(v, IGRAPH_ALL, constrained_partition->membership());
          all_neigh_comms_incl_dupes.insert(all_neigh_comms_incl_dupes.end(), neigh_comm_layer.begin(), neigh_comm_layer.end());
        }
        if (all_neigh_comms_incl_dupes.size() > 0)
        {
          size_t random_idx = get_random_int(0, all_neigh_comms_incl_dupes.size() - 1, &rng);
          size_t rand_comm = all_neigh_comms_incl_dupes[random_idx];
          // No need to check if random_comm is already added, we only add one comm
          comms.push_back(rand_comm);
          comm_added[rand_comm] = true;
        }
    }

    #ifdef DEBUG
      cerr << "Consider " << comms.size() << " communities for moving." << endl;
    #endif

    size_t max_comm = v_comm;
    double max_improv = (0 < max_comm_size && max_comm_size < partitions[0]->csize(v_comm)) ? -INFINITY : 10*DBL_EPSILON;
    size_t v_size = graphs[0]->node_size(v);
    for (size_t comm : comms)
    {
      // Do not create too-large communities.
      if (0 < max_comm_size && max_comm_size < partitions[0]->csize(comm) + v_size) {
        continue;
      }

      double possible_improv = 0.0;

      // Consider the improvement of moving to a community for all layers
      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        // Make sure to multiply it by the weight per layer
        possible_improv += layer_weights[layer]*partitions[layer]->diff_move(v, comm);
      }

      // Check if improvement is best
      if (possible_improv > max_improv)
      {
        max_comm = comm;
        max_improv = possible_improv;
      }
    }

    is_node_stable[v] = true;

    // If we actually plan to move the nove
    if (max_comm != v_comm)
    {
      // Keep track of improvement
      total_improv += max_improv;

      #ifdef DEBUG
        // If we are debugging, calculate quality function
        double q_improv = 0;
      #endif

      for (size_t layer = 0; layer < nb_layers; layer++)
      {
        MutableVertexPartition* partition = partitions[layer];

        #ifdef DEBUG
          // If we are debugging, calculate quality function
          double q1 = partition->quality();
        #endif

        // Actually move the node
        partition->move_node(v, max_comm);
        #ifdef DEBUG
          // If we are debugging, calculate quality function
          // and report difference
          double q2 = partition->quality();
          double q_delta = layer_weights[layer]*(q2 - q1);
          q_improv += q_delta;
          cerr << "Move node " << v
          << " from " << v_comm << " to " << max_comm << " for layer " << layer
          << " (diff_move=" << max_improv
          << ", q2 - q1=" << q_delta << ")" << endl;
        #endif
      }
      #ifdef DEBUG
        if (fabs(q_improv - max_improv) > 1e-6)
        {
          cerr << "ERROR: Inconsistency while moving nodes, improvement as measured by quality function did not equal the improvement measured by the diff_move function." << endl
               << " (diff_move=" << max_improv
               << ", q2 - q1=" << q_improv << ")" << endl;
        }
      #endif

      // Mark neighbours as unstable (if not in new community and not fixed)
      for (Graph* graph : graphs)
      {
        for (size_t u : graph->get_neighbours(v, IGRAPH_ALL))
        {
          // If the neighbour was stable and is not in the new community, we
          // should mark it as unstable, and add it to the queue, skipping
          // fixed nodes
          if (is_node_stable[u] && partitions[0]->membership(u) != max_comm && constrained_partition->membership(u) == constrained_partition->membership(v))
          {
            vertex_order.push_back(u);
            is_node_stable[u] = false;
          }
        }
      }

      // Keep track of number of moves
      nb_moves += 1;
    }
    #ifdef DEBUG
      cerr << "Moved " << nb_moves << " nodes." << endl;
    #endif
  }
  partitions[0]->renumber_communities();
  vector<size_t> const& membership = partitions[0]->membership();
  for (size_t layer = 1; layer < nb_layers; layer++)
  {
    partitions[layer]->set_membership(membership);
    #ifdef DEBUG
      cerr << "Renumbered communities for layer " << layer << " for " << partitions[layer]->n_communities() << " communities." << endl;
    #endif //DEBUG
  }
  return total_improv;
}

double Optimiser::merge_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, MutableVertexPartition* constrained_partition)
{
  return this->merge_nodes_constrained(partitions, layer_weights, this->refine_consider_comms, constrained_partition);
}

double Optimiser::merge_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition)
{
  return this->merge_nodes_constrained(partitions, layer_weights, refine_consider_comms, constrained_partition, this->max_comm_size);
}

double Optimiser::merge_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)
{
  #ifdef DEBUG
    cerr << "double Optimiser::merge_nodes_constrained(vector<MutableVertexPartition*> partitions, vector<double> layer_weights, int consider_comms, MutableVertexPartition* constrained_partition, size_t max_comm_size)" << std::endl;
  #endif

  // Number of multiplex layers
  size_t nb_layers = partitions.size();
  if (nb_layers == 0)
    return -1.0;

  // Get graphs
  vector<Graph*> graphs(nb_layers);
  for (size_t layer = 0; layer < nb_layers; layer++)
    graphs[layer] = partitions[layer]->get_graph();
  // Number of nodes in the graph
  size_t n = graphs[0]->vcount();

  // Total improvement while merging nodes
  double total_improv = 0.0;

  for (size_t layer = 0; layer < nb_layers; layer++)
    if (graphs[layer]->vcount() != n)
      throw Exception("Number of nodes are not equal for all graphs.");

  // Establish vertex order
  // We normally initialize the normal vertex order
  // of considering node 0,1,...
  vector<size_t> vertex_order = range(n);


  // But if we use a random order, we shuffle this order.
  shuffle(vertex_order, &rng);

  vector< vector<size_t> > constrained_comms = constrained_partition->get_communities();

  vector<bool> comm_added(partitions[0]->n_communities(), false);
  vector<size_t> comms;

  // For each node
  for (size_t v : vertex_order)
  {
    // What is the current community of the node (this should be the same for all layers)
    size_t v_comm = partitions[0]->membership(v);

    if (partitions[0]->cnodes(v_comm) == 1)
    {
      // Clear comms
      for (size_t comm : comms)
        comm_added[comm] = false;
      comms.clear();

      if (consider_comms == ALL_COMMS)
      {
          // Add all communities to the set comms that are within the constrained community.
          size_t v_constrained_comm = constrained_partition->membership(v);
          for (size_t u : constrained_comms[v_constrained_comm])
          {
            size_t u_comm = partitions[0]->membership(u);
            if (!comm_added[u_comm]) {
              comms.push_back(u_comm);
              comm_added[u_comm] = true;
            }
          }
      }
      else if (consider_comms == ALL_NEIGH_COMMS)
      {
          /****************************ALL NEIGH COMMS*****************************/
          for (size_t layer = 0; layer < nb_layers; layer++)
          {
            for (size_t u : partitions[layer]->get_graph()->get_neighbours(v, IGRAPH_ALL)) {
              if (constrained_partition->membership(v) == constrained_partition->membership(u)) {
                size_t comm = partitions[layer]->membership(u);
                if (!comm_added[comm]) {
                  comms.push_back(comm);
                  comm_added[comm] = true;
                }
              }
            }
          }
      }
      else if (consider_comms == RAND_COMM)
      {
        /****************************RAND COMM***********************************/
          size_t v_constrained_comm = constrained_partition->membership(v);
          size_t random_idx = get_random_int(0, constrained_comms[v_constrained_comm].size() - 1, &rng);
          size_t rand_comm = constrained_comms[v_constrained_comm][random_idx];
          // No need to check if random_comm is already added, we only add one comm
          comms.push_back(rand_comm);
          comm_added[rand_comm] = true;
      }
      else if (consider_comms == RAND_NEIGH_COMM)
      {
        /****************************RAND NEIGH COMM*****************************/
          // Draw a random community among the neighbours, proportional to the
          // frequency of the communities among the neighbours. Notice this is no
          // longer
          vector<size_t> all_neigh_comms_incl_dupes;
          for (size_t layer = 0; layer < nb_layers; layer++)
          {
            vector<size_t> neigh_comm_layer = partitions[layer]->get_neigh_comms(v, IGRAPH_ALL, constrained_partition->membership());
            all_neigh_comms_incl_dupes.insert(all_neigh_comms_incl_dupes.end(), neigh_comm_layer.begin(), neigh_comm_layer.end());
          }
          size_t k = all_neigh_comms_incl_dupes.size();
          if (k > 0)
          {
            // Make sure there is also a probability not to move the node
            if (get_random_int(0, k, &rng) > 0)
            {
              size_t random_idx = get_random_int(0, k - 1, &rng);
              size_t rand_comm = all_neigh_comms_incl_dupes[random_idx];
              // No need to check if random_comm is already added, we only add one comm
              comms.push_back(rand_comm);
              comm_added[rand_comm] = true;
            }
          }
      }

      #ifdef DEBUG
        cerr << "Consider " << comms.size() << " communities for moving." << endl;
      #endif

      size_t max_comm = v_comm;
      double max_improv = (0 < max_comm_size && max_comm_size < partitions[0]->csize(v_comm)) ? -INFINITY : 0;
      size_t v_size = graphs[0]->node_size(v);
      for (size_t comm : comms)
      {
        // reset comm_added to all false
        comm_added[comm] = false;

        // Do not create too-large communities.
        if (0 < max_comm_size && max_comm_size < partitions[0]->csize(comm) + v_size) {
          continue;
        }

        double possible_improv = 0.0;

        // Consider the improvement of moving to a community for all layers
        for (size_t layer = 0; layer < nb_layers; layer++)
        {
          // Make sure to multiply it by the weight per layer
          possible_improv += layer_weights[layer]*partitions[layer]->diff_move(v, comm);
        }

        if (possible_improv >= max_improv)
        {
          max_comm = comm;
          max_improv = possible_improv;
        }
      }

      // If we actually plan to move the node
      if (max_comm != v_comm)
      {
          // Keep track of improvement
          total_improv += max_improv;

          #ifdef DEBUG
            // If we are debugging, calculate quality function
            double q_improv = 0;
          #endif

          for (size_t layer = 0; layer < nb_layers; layer++)
          {
            MutableVertexPartition* partition = partitions[layer];

            #ifdef DEBUG
              // If we are debugging, calculate quality function
              double q1 = partition->quality();
            #endif

            // Actually move the node
            partition->move_node(v, max_comm);
            #ifdef DEBUG
              // If we are debugging, calculate quality function
              // and report difference
              double q2 = partition->quality();
              double q_delta = layer_weights[layer]*(q2 - q1);
              q_improv += q_delta;
              cerr << "Move node " << v
              << " from " << v_comm << " to " << max_comm << " for layer " << layer
              << " (diff_move=" << max_improv
              << ", q2 - q1=" << q_delta << ")" << endl;
            #endif
          }
          #ifdef DEBUG
            if (fabs(q_improv - max_improv) > 1e-6)
            {
              cerr << "ERROR: Inconsistency while moving nodes, improvement as measured by quality function did not equal the improvement measured by the diff_move function." << endl
                   << " (diff_move=" << max_improv
                   << ", q2 - q1=" << q_improv << ")" << endl;
            }
          #endif
        }
      }
  }

  partitions[0]->renumber_communities();
  vector<size_t> const& membership = partitions[0]->membership();
  for (size_t layer = 1; layer < nb_layers; layer++)
  {
    partitions[layer]->set_membership(membership);
    #ifdef DEBUG
      cerr << "Renumbered communities for layer " << layer << " for " << partitions[layer]->n_communities() << " communities." << endl;
    #endif //DEBUG
  }
  return total_improv;
}
