ChowLiuTree.h

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#pragma once

#include <string>
#include <vector>
#include <list>
#include <map>
#include <sstream>
#include <Eigen/Dense>

#include "Node.h"


namespace isam {


class ChowLiuTreeInfo {

private:

  const Eigen::MatrixXd& _L;
  const std::vector<Node *>& _nodes;

public:

  ChowLiuTreeInfo (const Eigen::MatrixXd& L, const std::vector<Node *>& nodes)
      : _L(L), _nodes(nodes) { }

  //const std::vector<Node *>& nodes() {return _nodes;}
  int num_nodes() {return _nodes.size();}

  Eigen::MatrixXd marginal(int id);

  Eigen::MatrixXd joint(int ida, int idb); // a, b

  Eigen::MatrixXd conditional(int ida, int idb);

};

class ChowLiuTreeNode {

public:
  
  int id;
  int pid;
  std::vector<int> cids;
  Eigen::MatrixXd marginal;     // marginal information
  Eigen::MatrixXd conditional;  // conditional information with parrent
  Eigen::MatrixXd joint;        // joint information with parrent
  
  bool is_root () { return (pid == -1) ? true : false; }
  bool is_leaf () { return (cids.size() == 0) ? true : false; }

};

class MI {
  
public:
  int id1;
  int id2;
  double mi;

  MI (int id1_, int id2_, double mi_)
    : id1(id1_), id2(id2_), mi(mi_){
  }

};



class ChowLiuTree {

  ChowLiuTreeInfo _clt_info;
  std::list<MI> _edges;

  void _calc_edges();
  double _calc_mi(int ida, int idb);
  void _max_span_tree();
  void _build_tree_rec(int id, int pid);

public:

  // the resulting chow-liu tree
  std::map<int, ChowLiuTreeNode> tree;

  ChowLiuTree (const Eigen::MatrixXd &L, const std::vector<Node *>& nodes);
  
};


} // namespace isam