69 lines
1.9 KiB
C++
69 lines
1.9 KiB
C++
/*
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* EliminationTree.h
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* Created on: Feb 4, 2010
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* @Author: Kai Ni
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* @Author: Frank Dellaert
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* @brief: The elimination tree
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*/
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#pragma once
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#include <set>
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#include <gtsam/inference/IndexTable.h>
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#include <gtsam/inference/ClusterTree.h>
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namespace gtsam {
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/**
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* An elimination tree (see Gilbert01bit) associated with a factor graph and an ordering
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* is a cluster-tree where there is one node j for each variable, and the parent of each node
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* corresponds to the first variable up the ordering in the Cholesky factor that j is connected to.
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*/
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template<class FG>
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class EliminationTree: public ClusterTree<FG> {
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public:
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// In an elimination tree, the clusters are called nodes
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typedef typename ClusterTree<FG>::Cluster Node;
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typedef typename Node::shared_ptr sharedNode;
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// we typedef the following handy list of ordered factor graphs
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typedef std::pair<Symbol, FG> NamedGraph;
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typedef std::list<NamedGraph> OrderedGraphs;
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private:
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/** Number of variables */
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size_t nrVariables_;
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/** Map from ordering index to Nodes */
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typedef std::vector<sharedNode> Nodes;
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Nodes nodes_;
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/**
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* add a factor graph fragment with given frontal key into the tree. Assumes
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* parent node was already added (will throw exception if not).
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*/
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void add(const FG& fg, const Symbol& key, const IndexTable<Symbol>& indexTable);
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public:
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/**
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* Constructor variant 1: from an ordered list of factor graphs
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* The list is supposed to be in elimination order, and for each
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* eliminated variable a list of factors to be eliminated.
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* This function assumes the input is correct (!) and will not check
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* whether the factors refer only to the correct set of variables.
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*/
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EliminationTree(const OrderedGraphs& orderedGraphs);
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/**
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* Constructor variant 2: given a factor graph and the elimination ordering
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*/
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EliminationTree(FG& fg, const Ordering& ordering);
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}; // EliminationTree
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} // namespace gtsam
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