DFSTree.h

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/**
 *
 *   Copyright (c) 2005-2021 by Pierre-Henri WUILLEMIN(@LIP6) & Christophe GONZALES(@AMU)
 *   info_at_agrum_dot_org
 *
 *  This library is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */


/**
 * @file
 * @brief Headers of the DFSTree class.
 *
 * @author Lionel TORTI and Pierre-Henri WUILLEMIN(@LIP6)
 */

#ifndef GUM_DFS_TREE_H
#define GUM_DFS_TREE_H

#include <list>
#include <ostream>
#include <utility>
#include <vector>

#include <agrum/tools/core/math/math_utils.h>
#include <agrum/tools/core/bijection.h>
#include <agrum/tools/core/sequence.h>
#include <agrum/tools/core/set.h>

#include <agrum/tools/graphs/diGraph.h>

#include <agrum/tools/graphs/algorithms/triangulations/partialOrderedTriangulation.h>

#include <agrum/PRM/gspan/edgeGrowth.h>
#include <agrum/PRM/gspan/interfaceGraph.h>
#include <agrum/PRM/gspan/pattern.h>

#include <agrum/PRM/gspan/searchStrategy.h>

namespace gum {
  namespace prm {

    template < typename GUM_SCALAR >
    class GSpan;

    namespace gspan {
      template < typename GUM_SCALAR >
      class SearchStrategy;

      /**
       * @class DFSTree
       * @headerfile DFSTree.h <agrum/PRM/gspan/DFSTree.h>
       *
       * A DFSTree is used by gspan to sort lexicographically patterns
       * discovered in an interface graph.
       */
      template < typename GUM_SCALAR >
      class DFSTree: private DiGraph {
        public:
        // =========================================================================
        /// @name Constructor and destructor.
        // ==========================================================================
        /// @{

        /// Default constructor.
        // DFSTree(InterfaceGraph<GUM_SCALAR>* graph);
        DFSTree(const InterfaceGraph< GUM_SCALAR >& graph,
                SearchStrategy< GUM_SCALAR >*       strategy = 0);

        /// Destructor.
        ~DFSTree();

        /// @}
        // =========================================================================
        /// @name DFSTree getters and setters.
        // ==========================================================================
        /// @{

        const InterfaceGraph< GUM_SCALAR >& graph() const;

        struct PatternData {
          /// Constructor.
          explicit PatternData(Pattern* p);
          /// Copy constructor.
          PatternData(const PatternData& from);
          /// Destructor.
          ~PatternData();
          /// The pattern.
          Pattern* pattern;
          /// The list of the pattern's children, sorted lexicographically.
          std::list< NodeId > children;
          /// The isomorphism graph of the pattern.
          UndiGraph iso_graph;
          /// The instances matching p in the interface graph.
          NodeProperty< Sequence< PRMInstance< GUM_SCALAR >* >* > iso_map;
          /// The maximal independent set of p.
          Set< NodeId > max_indep_set;
          /// The cost of this Pattern
          Size cost;
          /// The gain of this Pattern
          Size gain;
        };

        /// Returns the list of root patterns in this DFSTree.
        std::list< NodeId >& roots();

        /// Returns the list of root patterns in this DFSTree.
        const std::list< NodeId >& roots() const;

        /// Returns the parent of p in this DFSTree.
        Pattern& parent(const Pattern& p);

        /// Returns the parent of p in this DFSTree.
        const Pattern& parent(const Pattern& p) const;

        /// Returns the list of p children in this DFSTree.
        std::list< NodeId >& children(const Pattern& p);

        /// Returns the list of p children in this DFSTree.
        const std::list< NodeId >& children(const Pattern& p) const;

        /// Returns the pattern represented by id in this DFSTree.
        Pattern& pattern(NodeId id);

        /// Returns the pattern represented by id in this DFSTree.
        const Pattern& pattern(NodeId id) const;

        /**
         * @brief Add a one edge Pattern in this DFSTree.
         *
         * @param data Data over the edge used to create a root of this DFSTree.
         * @return Returns the Pattern added as a root of this DFSTree.
         */
        void addRoot(LabelData& data);

        /**
         * @brief Add a one edge growth of p as one of its child.
         *
         * The child is inserted lexicographically among the children of p.
         * However if the child is found to be not minimal an
         * OperationNotAllowed is raised.
         *
         * @param p The Pattern from which a one edge growth is spawned.
         * @param edge_growth The data about the edge growth of p.
         * @param min_freq minimum number of occurrence to be used as a pattern
         *
         * @throw FatalError Raised if the grow is an illegal backedge growth.
         * @throw OperationNotAllowed Raised if the grow is found to be not
         *minimal.
         */
        Pattern& growPattern(Pattern& p, EdgeGrowth< GUM_SCALAR >& edge_growth, Size min_freq);

        /// @}
        // =========================================================================
        /// @name Isomorphisms for patterns in this DFSTree.
        // ==========================================================================
        /// @{

        /**
         * @brief Returns the isomorphism graph of p in the interface graph.
         *
         * The isomorphism graph is a undirected graph in which each node
         *represents
         * a set of PRMInstance<GUM_SCALAR> matching p in the interface graph.
         *
         * If there exists an edge between two nodes in the isomorphism graph,
         *then
         * the two respective set of instances are not disjoint.
         *
         * @param p The pattern for which we want the isomorphism graph.
         * @return The isomorphism graph of p.
         *
         * @throw NotFound Raised if p is not a node in this DFSTree.
         */
        UndiGraph& iso_graph(const Pattern& p);

        /**
         * @brief Given a pattern and a node in its isomorphism graph, this
         *methods
         *        returns the sequence of instance matching p in the interface
         *graph.
         *
         * The sequence of instances respect DSF subscripting. Each node in the
         * pattern's graph have a DSF subscript from 1 to n, where n is the
         *number
         * of nodes in the pattern's graph.
         *
         * If for a given match you want the k-th instance repecting p's DFS
         *subscripting,
         * then it will be the (k - 1)th element in the sequence.
         *
         * @param p The pattern for which we want a match in the interface
         *graph.
         * @param node The node in p isomorphism graph for which we want the
         *matching
         *             set if instances.
         * @return Returns the sequence of instances matching p and node.
         *
         * @throw NotFound Raised if p or node does not exists.
         */
        Sequence< PRMInstance< GUM_SCALAR >* >& iso_map(const Pattern& p, NodeId node);

        /**
         * @brief Returns the maximal independent set of p isomorphism graph.
         *
         * @param p The pattern for which we want its maximal independent set.
         *
         * @throw NotFound Raised if p is not a node in this DFSTree.
         */
        Set< NodeId >& max_indep_set(const Pattern& p);

        /// Returns the frequency of p respecting it's maximal independent set.
        /// @param p The pattern
        double frequency(const Pattern& p) const;

        /// @param p The pattern
        PatternData& data(const Pattern& p);
        /// @param p The pattern
        const PatternData& data(const Pattern& p) const;

        /// strategy getter
        SearchStrategy< GUM_SCALAR >& strategy();

        /// strategy getter
        const SearchStrategy< GUM_SCALAR >& strategy() const;

        /** @class NeighborDegreeSort
         * @headerfile DFSTree.h <agrum/PRM/gspan/DFSTree.h>
         * @brief This is used to generate the max_indep_set of a Pattern.
         */
        struct NeighborDegreeSort {
          /// Constructor
          explicit NeighborDegreeSort(UndiGraph& graph);
          /// Copy constructor.
          NeighborDegreeSort(const NeighborDegreeSort& source);
          /// Destructor.
          ~NeighborDegreeSort();
          /// The operator used to sort stuff.
          bool operator()(NodeId i, NodeId j);
          /// The isomorphism graph.
          UndiGraph& g;
        };

        /// @}

        private:
        /// The interface graph on which this DFSTree applies.
        const InterfaceGraph< GUM_SCALAR >* _graph_;

        /// The list of root patterns in this DFSTree.
        std::list< NodeId > _roots_;

        /// The mapping between nodes in this DFSTree and the patterns they
        /// represents.
        Bijection< NodeId, Pattern* > _node_map_;

        /// Data about patterns in this DFSTree.
        HashTable< Pattern*, PatternData* > _data_;

        /// The strategy used to prune the search tree.
        SearchStrategy< GUM_SCALAR >* _strategy_;

        /// Raise different exceptions if child is invalid or illegal
        void _checkGrowth_(Pattern& p, Pattern* child, EdgeGrowth< GUM_SCALAR >& edge_growth);

        /// Add a child to this DFSTree.
        void _addChild_(Pattern& p, Pattern* child, EdgeGrowth< GUM_SCALAR >& edge_growth);

        /// Check if an instance match is redundant.
        bool _is_new_seq_(Sequence< PRMInstance< GUM_SCALAR >* >&                  seq,
                          NodeProperty< Sequence< PRMInstance< GUM_SCALAR >* >* >& iso_map);

        /// This initialize the DSFTree with a new root.
        /// @param p A Pattern.
        /// @param seq A sequence of EdgeData<GUM_SCALAR>.
        void _initialiaze_root_(Pattern* p, Sequence< EdgeData< GUM_SCALAR >* >& seq);

        // Used by  _find_sub_pattern_.
        bool _test_equality_(HashTable< PRMClassElement< GUM_SCALAR >*, Size >& x,
                             HashTable< PRMClassElement< GUM_SCALAR >*, Size >& y);
      };


#ifndef GUM_NO_EXTERN_TEMPLATE_CLASS
      extern template class DFSTree< double >;
#endif


    } /* namespace gspan */
  }   /* namespace prm */
} /* namespace gum */

#include <agrum/PRM/gspan/DFSTree_tpl.h>

#endif /* GUM_DFS_TREE_H */