/* This file is part of libDAI - http://www.libdai.org/
*
* Copyright (c) 2006-2011, The libDAI authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
*/
/// \file
/// \brief Defines classes Region, FRegion and RegionGraph, which implement a particular subclass of region graphs.
#ifndef __defined_libdai_regiongraph_h
#define __defined_libdai_regiongraph_h
#include
#include
#include
#include
namespace dai {
/// A Region is a set of variables with a counting number
class Region : public VarSet {
private:
/// Counting number
Real _c;
public:
/// Default constructor
Region() : VarSet(), _c(1.0) {}
/// Construct from a set of variables and a counting number
Region( const VarSet& x, Real c ) : VarSet(x), _c(c) {}
/// Returns constant reference to counting number
const Real& c() const { return _c; }
/// Returns reference to counting number
Real& c() { return _c; }
};
/// An FRegion is a factor with a counting number
class FRegion : public Factor {
private:
/// Counting number
Real _c;
public:
/// Default constructor
FRegion() : Factor(), _c(1.0) {}
/// Constructs from a factor and a counting number
FRegion( const Factor& x, Real c ) : Factor(x), _c(c) {}
/// Returns constant reference to counting number
const Real& c() const { return _c; }
/// Returns reference to counting number
Real& c() { return _c; }
};
/// A RegionGraph combines a bipartite graph consisting of outer regions (type FRegion) and inner regions (type Region) with a FactorGraph
/** A RegionGraph inherits from a FactorGraph and adds additional structure in the form of a "region graph". Our definition of region graph
* is inspired by [\ref HAK03], which is less general than the definition given in [\ref YFW05].
*
* The extra structure described by a RegionGraph compared with that described by a FactorGraph is:
* - a set of outer regions (indexed by \f$\alpha\f$), where each outer region consists of
* - a factor defined on a subset of variables
* - a counting number
* - a set of inner regions (indexed by \f$\beta\f$), where each inner region consists of
* - a subset of variables
* - a counting number
* - edges between inner and outer regions
*
* Each factor in the factor graph belongs to an outer region; normally, the factor contents
* of an outer region would be the product of all the factors that belong to that region.
* \idea Generalize the definition of region graphs to the one given in [\ref YFW05], i.e., replace
* the current implementation which uses a BipartiteGraph with one that uses a DAG.
* \idea The outer regions are products of factors; right now, this product is constantly cached:
* changing one factor results in an update of all relevant outer regions. This may not be the most
* efficient approach; an alternative would be to only precompute the factor products at the start
* of an inference algorithm - e.g., in init(). This has the additional advantage that FactorGraph
e can offer write access to its factors.
*/
class RegionGraph : public FactorGraph {
protected:
/// Stores the neighborhood structure
BipartiteGraph _G;
/// The outer regions (corresponding to nodes of type 1)
std::vector _ORs;
/// The inner regions (corresponding to nodes of type 2)
std::vector _IRs;
/// Stores for each factor index the index of the outer region it belongs to
std::vector _fac2OR;
public:
/// \name Constructors and destructors
//@{
/// Default constructor
RegionGraph() : FactorGraph(), _G(), _ORs(), _IRs(), _fac2OR() {}
/// Constructs a region graph from a factor graph, a vector of outer regions, a vector of inner regions and a vector of edges
/** The counting numbers for the outer regions are set to 1.
*/
RegionGraph( const FactorGraph& fg, const std::vector& ors, const std::vector& irs, const std::vector >& edges ) : FactorGraph(), _G(), _ORs(), _IRs(), _fac2OR() {
construct( fg, ors, irs, edges );
// Check counting numbers
#ifdef DAI_DEBUG
checkCountingNumbers();
#endif
}
/// Constructs a region graph from a factor graph and a vector of outer clusters (CVM style)
/** The region graph is constructed as in the Cluster Variation Method.
*
* The outer regions have as variable subsets the clusters specified in \a cl.
* Each factor in the factor graph \a fg is assigned to one of the outer regions.
* Each outer region gets counting number 1.
*
* The inner regions are (repeated) intersections of outer regions.
* An inner and an outer region are connected if the variables in the inner region form a
* subset of the variables in the outer region. The counting numbers for the inner
* regions are calculated by calcCountingNumbers() and satisfy the Moebius formula.
*/
RegionGraph( const FactorGraph& fg, const std::vector& cl ) : FactorGraph(), _G(), _ORs(), _IRs(), _fac2OR() {
constructCVM( fg, cl );
// Check counting numbers
#ifdef DAI_DEBUG
checkCountingNumbers();
#endif
}
/// Clone \c *this (virtual copy constructor)
virtual RegionGraph* clone() const { return new RegionGraph(*this); }
//@}
/// \name Accessors and mutators
//@{
/// Returns number of outer regions
size_t nrORs() const { return _ORs.size(); }
/// Returns number of inner regions
size_t nrIRs() const { return _IRs.size(); }
/// Returns constant reference to outer region \a alpha
const FRegion& OR( size_t alpha ) const {
DAI_DEBASSERT( alpha < nrORs() );
return _ORs[alpha];
}
/// Returns reference to outer region \a alpha
FRegion& OR( size_t alpha ) {
DAI_DEBASSERT( alpha < nrORs() );
return _ORs[alpha];
}
/// Returns constant reference to inner region \a beta
const Region& IR( size_t beta ) const {
DAI_DEBASSERT( beta < nrIRs() );
return _IRs[beta];
}
/// Returns reference to inner region \a beta
Region& IR( size_t beta ) {
DAI_DEBASSERT( beta < nrIRs() );
return _IRs[beta];
}
/// Returns the index of the outer region to which the \a I 'th factor corresponds
size_t fac2OR( size_t I ) const {
DAI_DEBASSERT( I < nrFactors() );
DAI_DEBASSERT( I < _fac2OR.size() );
return _fac2OR[I];
}
/// Returns constant reference to the neighbors of outer region \a alpha
const Neighbors& nbOR( size_t alpha ) const { return _G.nb1(alpha); }
/// Returns constant reference to the neighbors of inner region \a beta
const Neighbors& nbIR( size_t beta ) const { return _G.nb2(beta); }
/// Returns DAG structure of the region graph
/** \note Currently, the DAG is implemented as a BipartiteGraph; the nodes of
* type 1 are the outer regions, the nodes of type 2 the inner regions, and
* edges correspond with arrows from nodes of type 1 to type 2.
*/
const BipartiteGraph& DAG() const { return _G; }
//@}
/// \name Queries
//@{
/// Check whether the counting numbers are valid
/** Counting numbers are said to be (variable) valid if for each variable \f$x\f$,
* \f[\sum_{\alpha \ni x} c_\alpha + \sum_{\beta \ni x} c_\beta = 1\f]
* or in words, if the sum of the counting numbers of the regions
* that contain the variable equals one.
*/
bool checkCountingNumbers() const;
//@}
/// \name Operations
//@{
/// Set the content of the \a I 'th factor and make a backup of its old content if \a backup == \c true
virtual void setFactor( size_t I, const Factor& newFactor, bool backup = false ) {
FactorGraph::setFactor( I, newFactor, backup );
recomputeOR( I );
}
/// Set the contents of all factors as specified by \a facs and make a backup of the old contents if \a backup == \c true
virtual void setFactors( const std::map& facs, bool backup = false ) {
FactorGraph::setFactors( facs, backup );
VarSet ns;
for( std::map::const_iterator fac = facs.begin(); fac != facs.end(); fac++ )
ns |= fac->second.vars();
recomputeORs( ns );
}
//@}
/// \name Input/output
//@{
/// Reads a region graph from a file
/** \note Not implemented yet
*/
virtual void ReadFromFile( const char* /*filename*/ ) {
DAI_THROW(NOT_IMPLEMENTED);
}
/// Writes a factor graph to a file
/** \note Not implemented yet
*/
virtual void WriteToFile( const char* /*filename*/, size_t /*precision*/=15 ) const {
DAI_THROW(NOT_IMPLEMENTED);
}
/// Writes a RegionGraph to an output stream
friend std::ostream& operator<< ( std::ostream& os, const RegionGraph& rg );
/// Writes a region graph to a GraphViz .dot file
/** \note Not implemented yet
*/
virtual void printDot( std::ostream& /*os*/ ) const {
DAI_THROW(NOT_IMPLEMENTED);
}
//@}
protected:
/// Helper function for constructors
void construct( const FactorGraph& fg, const std::vector& ors, const std::vector& irs, const std::vector >& edges );
/// Helper function for constructors (CVM style)
void constructCVM( const FactorGraph& fg, const std::vector& cl, size_t verbose=0 );
/// Recompute all outer regions
/** The factor contents of each outer region is set to the product of the factors belonging to that region.
*/
void recomputeORs();
/// Recompute all outer regions involving the variables in \a vs
/** The factor contents of each outer region involving at least one of the variables in \a vs is set to the product of the factors belonging to that region.
*/
void recomputeORs( const VarSet& vs );
/// Recompute all outer regions involving factor \a I
/** The factor contents of each outer region involving the \a I 'th factor is set to the product of the factors belonging to that region.
*/
void recomputeOR( size_t I );
/// Calculates counting numbers of inner regions based upon counting numbers of outer regions
/** The counting numbers of the inner regions are set using the Moebius inversion formula:
* \f[ c_\beta := 1 - \sum_{\gamma \in \mathrm{an}(\beta)} c_\gamma \f]
* where \f$\mathrm{an}(\beta)\f$ are the ancestors of inner region \f$\beta\f$ according to
* the partial ordering induced by the subset relation (i.e., a region is a child of another
* region if its variables are a subset of the variables of its parent region).
*/
void calcCVMCountingNumbers();
};
} // end of namespace dai
#endif