106 lines
3.7 KiB
C++
106 lines
3.7 KiB
C++
/*
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* JunctionTree-inl.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 junction tree, template bodies
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*/
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#pragma once
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#include <boost/foreach.hpp>
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#include "SymbolicFactorGraph.h"
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#include "BayesTree-inl.h"
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#include "JunctionTree.h"
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namespace gtsam {
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using namespace std;
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/* ************************************************************************* */
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template <class FG>
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JunctionTree<FG>::JunctionTree(FG& fg, const Ordering& ordering) {
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// Symbolic factorization: GaussianFactorGraph -> SymbolicFactorGraph
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// -> SymbolicBayesNet -> SymbolicBayesTree
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SymbolicFactorGraph sfg(fg);
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SymbolicBayesNet sbn = sfg.eliminate(ordering);
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BayesTree<SymbolicConditional> sbt(sbn);
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// distribtue factors
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this->root_ = distributeFactors(fg, sbt.root());
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}
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/* ************************************************************************* */
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template<class FG>
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typename JunctionTree<FG>::sharedClique JunctionTree<FG>::distributeFactors(
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FG& fg, const BayesTree<SymbolicConditional>::sharedClique bayesClique) {
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// create a new clique in the junction tree
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sharedClique clique(new Clique());
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clique->frontal_ = bayesClique->ordering();
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clique->separator_.insert(bayesClique->separator_.begin(),
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bayesClique->separator_.end());
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// recursively call the children
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BOOST_FOREACH(const BayesTree<SymbolicConditional>::sharedClique bayesChild, bayesClique->children()) {
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sharedClique child = distributeFactors(fg, bayesChild);
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clique->children_.push_back(child);
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child->parent_ = clique;
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}
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// collect the factors
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typedef vector<typename FG::sharedFactor> Factors;
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BOOST_FOREACH(const Symbol& frontal, clique->frontal_) {
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Factors factors = fg.template findAndRemoveFactors(frontal);
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BOOST_FOREACH(const typename FG::sharedFactor& factor_, factors)
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clique->push_back(factor_);
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}
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return clique;
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}
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/* ************************************************************************* */
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template <class FG> template <class Conditional>
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pair<FG, typename BayesTree<Conditional>::sharedClique>
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JunctionTree<FG>::eliminateOneClique(sharedClique current) {
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typedef typename BayesTree<Conditional>::sharedClique sharedBtreeClique;
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FG fg; // factor graph will be assembled from local factors and marginalized children
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list<sharedBtreeClique> children;
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fg.push_back(*current); // add the local factor graph
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BOOST_FOREACH(sharedClique& child, current->children_) {
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// receive the factors from the child and its clique point
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FG fgChild; sharedBtreeClique childRoot;
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boost::tie(fgChild, childRoot) = eliminateOneClique<Conditional>(child);
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fg.push_back(fgChild);
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children.push_back(childRoot);
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}
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// eliminate the combined factors
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// warning: fg is being eliminated in-place and will contain marginal afterwards
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BayesNet<Conditional> bn = fg.eliminateFrontals(current->frontal_);
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// create a new clique corresponding the combined factors
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// BayesTree<Conditional> bayesTree(bn, children);
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sharedBtreeClique new_clique(new typename BayesTree<Conditional>::Clique(bn));
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new_clique->children_ = children;
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BOOST_FOREACH(sharedBtreeClique& childRoot, children)
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childRoot->parent_ = new_clique;
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return make_pair(fg, new_clique);
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}
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/* ************************************************************************* */
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template <class FG> template <class Conditional>
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typename BayesTree<Conditional>::sharedClique JunctionTree<FG>::eliminate() {
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pair<FG, typename BayesTree<Conditional>::sharedClique> ret = this->eliminateOneClique<Conditional>(this->root());
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if (ret.first.nrFactors() != 0)
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throw runtime_error("JuntionTree::eliminate: elimination failed because of factors left over!");
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return ret.second;
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}
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} //namespace gtsam
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