114 lines
4.3 KiB
C++
114 lines
4.3 KiB
C++
/* ----------------------------------------------------------------------------
|
|
|
|
* GTSAM Copyright 2010, Georgia Tech Research Corporation,
|
|
* Atlanta, Georgia 30332-0415
|
|
* All Rights Reserved
|
|
* Authors: Frank Dellaert, et al. (see THANKS for the full author list)
|
|
|
|
* See LICENSE for the license information
|
|
|
|
* -------------------------------------------------------------------------- */
|
|
|
|
/*
|
|
* JunctionTree.h
|
|
* Created on: Feb 4, 2010
|
|
* @author Kai Ni
|
|
* @author Frank Dellaert
|
|
* @brief: The junction tree
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <set>
|
|
#include <vector>
|
|
#include <gtsam/base/FastList.h>
|
|
#include <gtsam/inference/BayesTree.h>
|
|
#include <gtsam/inference/ClusterTree.h>
|
|
#include <gtsam/inference/IndexConditional.h>
|
|
#include <gtsam/inference/VariableIndex.h>
|
|
|
|
namespace gtsam {
|
|
|
|
/**
|
|
* In gtsam a junction tree is an intermediate data structure in multifrontal
|
|
* variable elimination. Each node is a cluster of factors, along with a
|
|
* clique of variables that are eliminated all at once. The tree structure and
|
|
* elimination method are exactly analagous to the EliminationTree, except that
|
|
* in the JunctionTree, at each node multiple variables are eliminated at the same
|
|
* time.
|
|
*
|
|
* A junction tree (or clique-tree) is a cluster-tree where each node k represents a
|
|
* clique (maximal fully connected subset) of an associated chordal graph, such as a
|
|
* chordal Bayes net resulting from elimination. In GTSAM the BayesTree is used to
|
|
* represent the clique tree associated with a Bayes net, and the JunctionTree is
|
|
* used to collect the factors associated with each clique during the elimination process.
|
|
*/
|
|
template<class FG>
|
|
class JunctionTree: public ClusterTree<FG> {
|
|
|
|
public:
|
|
|
|
/// In a junction tree each cluster is associated with a clique
|
|
typedef typename ClusterTree<FG>::Cluster Clique;
|
|
typedef typename Clique::shared_ptr sharedClique; ///< Shared pointer to a clique
|
|
|
|
/// The BayesTree type produced by elimination
|
|
typedef class BayesTree<typename FG::FactorType::ConditionalType> BayesTree;
|
|
|
|
/// Shared pointer to this class
|
|
typedef boost::shared_ptr<JunctionTree<FG> > shared_ptr;
|
|
|
|
/// We will frequently refer to a symbolic Bayes tree, used to find the clique structure
|
|
typedef gtsam::BayesTree<IndexConditional> SymbolicBayesTree;
|
|
|
|
private:
|
|
// distribute the factors along the cluster tree
|
|
sharedClique distributeFactors(const FG& fg,
|
|
const SymbolicBayesTree::sharedClique& clique);
|
|
|
|
// distribute the factors along the cluster tree
|
|
sharedClique distributeFactors(const FG& fg, const std::vector<FastList<size_t> >& targets,
|
|
const SymbolicBayesTree::sharedClique& clique);
|
|
|
|
// recursive elimination function
|
|
std::pair<typename BayesTree::sharedClique, typename FG::sharedFactor>
|
|
eliminateOneClique(typename FG::Eliminate function,
|
|
const boost::shared_ptr<const Clique>& clique, bool cache = false) const;
|
|
|
|
// internal constructor
|
|
void construct(const FG& fg, const VariableIndex& variableIndex);
|
|
|
|
public:
|
|
/** Default constructor */
|
|
JunctionTree() {}
|
|
|
|
/** Named constructor to build the junction tree of a factor graph. Note
|
|
* that this has to compute the column structure as a VariableIndex, so if you
|
|
* already have this precomputed, use the JunctionTree(const FG&, const VariableIndex&)
|
|
* constructor instead.
|
|
* @param factorGraph The factor graph for which to build the elimination tree
|
|
*/
|
|
JunctionTree(const FG& factorGraph);
|
|
|
|
/** Construct from a factor graph and pre-computed variable index.
|
|
* @param factorGraph The factor graph for which to build the junction tree
|
|
* @param structure The set of factors involving each variable. If this is not
|
|
* precomputed, you can call the JunctionTree(const FG&)
|
|
* constructor instead.
|
|
*/
|
|
JunctionTree(const FG& fg, const VariableIndex& variableIndex);
|
|
|
|
/** Eliminate the factors in the subgraphs to produce a BayesTree.
|
|
* @param function The function used to eliminate, see the namespace functions
|
|
* in GaussianFactorGraph.h
|
|
* @param cache Whether to cache the intermediate elimination factors for use in ISAM2 - this
|
|
* should always be false when called outside of ISAM2 (this will be fixed in the future).
|
|
* @return The BayesTree resulting from elimination
|
|
*/
|
|
typename BayesTree::sharedClique eliminate(typename FG::Eliminate function,
|
|
bool cache = false) const;
|
|
|
|
}; // JunctionTree
|
|
|
|
} // namespace gtsam
|