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Improved documentation for EliminationTree

release/4.3a0
Richard Roberts 2011-09-05 17:40:03 +00:00
parent 780ec6c2ad
commit 6512c6b822
1 changed files with 34 additions and 16 deletions
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50
gtsam/inference/EliminationTree.h
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@ -19,15 +19,18 @@ namespace gtsam {
/**
* An elimination tree is a data structure used intermediately during
* elimination, and it can be used to save work between multiple eliminations.
* elimination. In future versions it will be used to save work between
* multiple eliminations.
*
* When a variable is eliminated, a new factor is created, which will involve
* other variables. Of those, the first one that will be eliminated next, will
* need that factor. In the elimination tree, that first variable is exactly
* the parent of each variable. This yields a tree in general, and not a chain
* When a variable is eliminated, a new factor is created by combining that
* variable's neighboring factors. The new combined factor involves the combined
* factors' involved variables. When the lowest-ordered one of those variables
* is eliminated, it consumes that combined factor. In the elimination tree,
* that lowest-ordered variable is the parent of the variable that was eliminated to
* produce the combined factor. This yields a tree in general, and not a chain
* because of the implicit sparse structure of the resulting Bayes net.
*
* This structures is examined even more closely in a JunctionTree, which
* This structure is examined even more closely in a JunctionTree, which
* additionally identifies cliques in the chordal Bayes net.
*/
template<class FACTOR>
@ -35,11 +38,12 @@ class EliminationTree: public Testable<EliminationTree<FACTOR> > {
public:
typedef typename FACTOR::shared_ptr sharedFactor;
typedef boost::shared_ptr<EliminationTree<FACTOR> > shared_ptr;
typedef gtsam::BayesNet<typename FACTOR::ConditionalType> BayesNet;
typedef EliminationTree<FACTOR> This; ///< This class
typedef boost::shared_ptr<This> shared_ptr; ///< Shared pointer to this class
typedef typename FACTOR::shared_ptr sharedFactor; ///< Shared pointer to a factor
typedef gtsam::BayesNet<typename FACTOR::ConditionalType> BayesNet; ///< The BayesNet corresponding to FACTOR
/** typedef for an eliminate subroutine */
/** Typedef for an eliminate subroutine */
typedef typename FactorGraph<FACTOR>::Eliminate Eliminate;
private:
@ -48,9 +52,9 @@ private:
typedef FastList<shared_ptr> SubTrees;
typedef std::vector<typename FACTOR::ConditionalType::shared_ptr> Conditionals;
Index key_; /** index associated with root */
Factors factors_; /** factors associated with root */
SubTrees subTrees_; /** sub-trees */
Index key_; ///< index associated with root
Factors factors_; ///< factors associated with root
SubTrees subTrees_; ///< sub-trees
/** default constructor, private, as you should use Create below */
EliminationTree(Index key = 0) : key_(key) {}
@ -73,7 +77,7 @@ private:
*/
sharedFactor eliminate_(Eliminate function, Conditionals& conditionals) const;
// Allow access to constructor and add methods for testing purposes
/// Allow access to constructor and add methods for testing purposes
friend class ::EliminationTreeTester;
public:
@ -81,11 +85,21 @@ public:
/**
* Named constructor to build the elimination tree of a factor graph using
* pre-computed column structure.
* @param factorGraph The factor graph for which to build the elimination tree
* @param structure The set of factors involving each variable. If this is not
* precomputed, you can call the Create(const FactorGraph<DERIVEDFACTOR>&)
* named constructor instead.
* @return The elimination tree
*/
template<class DERIVEDFACTOR>
static shared_ptr Create(const FactorGraph<DERIVEDFACTOR>& factorGraph, const VariableIndex& structure);
/** Named constructor to build the elimination tree of a factor graph */
/** Named constructor to build the elimination 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 Create(const FactorGraph<DERIVEDFACTOR>&, const VariableIndex&)
* named constructor instead.
* @param factorGraph The factor graph for which to build the elimination tree
*/
template<class DERIVEDFACTOR>
static shared_ptr Create(const FactorGraph<DERIVEDFACTOR>& factorGraph);
@ -95,7 +109,11 @@ public:
/** Test whether the tree is equal to another */
bool equals(const EliminationTree& other, double tol = 1e-9) const;
/** Eliminate the factors to a Bayes Net */
/** Eliminate the factors to a Bayes Net
* @param function The function to use to eliminate, see the static member
* functions of GaussianFactorGraph
* @return The BayesNet resulting from elimination
*/
typename BayesNet::shared_ptr eliminate(Eliminate function) const;
};