include/dai/bp_dual.h

   1 /*  This file is part of libDAI - http://www.libdai.org/
   2  *
   3  *  Copyright (c) 2006-2011, The libDAI authors. All rights reserved.
   4  *
   5  *  Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
   6  */
   7
   8
   9 /// \file
  10 /// \brief Defines class BP_dual, which is used primarily by BBP.
  11 /// \idea BP_dual replicates a large part of the functionality of BP; would it not be more efficient to adapt BP instead?
  12 /// \author Frederik Eaton
  13
  14
  15 #ifndef __defined_libdai_bp_dual_h
  16 #define __defined_libdai_bp_dual_h
  17
  18
  19 #include <dai/daialg.h>
  20 #include <dai/factorgraph.h>
  21 #include <dai/enum.h>
  22
  23
  24 namespace dai {
  25
  26
  27 /// Calculates both types of BP messages and their normalizers from an InfAlg.
  28 /** BP_dual calculates "dual" versions of BP messages (both messages from factors
  29  *  to variables and messages from variables to factors), and normalizers, given an InfAlg.
  30  *  These are computed from the variable and factor beliefs of the InfAlg.
  31  *  This class is used primarily by BBP.
  32  *
  33  *  \author Frederik Eaton
  34  */
  35 class BP_dual {
  36     protected:
  37         /// Convenience label for storing edge properties
  38         template<class T>
  39         struct _edges_t : public std::vector<std::vector<T> > {};
  40
  41         /// Groups together the data structures for storing the two types of messages and their normalizers
  42         struct messages {
  43             /// Unnormalized variable->factor messages
  44             _edges_t<Prob> n;
  45             /// Normalizers of variable->factor messages
  46             _edges_t<Real> Zn;
  47             /// Unnormalized Factor->variable messages
  48             _edges_t<Prob> m;
  49             /// Normalizers of factor->variable messages
  50             _edges_t<Real> Zm;
  51         };
  52         /// Stores all messages
  53         messages _msgs;
  54
  55         /// Groups together the data structures for storing the two types of beliefs and their normalizers
  56         struct beliefs {
  57             /// Unnormalized variable beliefs
  58             std::vector<Prob> b1;
  59             /// Normalizers of variable beliefs
  60             std::vector<Real> Zb1;
  61             /// Unnormalized factor beliefs
  62             std::vector<Prob> b2;
  63             /// Normalizers of factor beliefs
  64             std::vector<Real> Zb2;
  65         };
  66         /// Stores all beliefs
  67         beliefs _beliefs;
  68
  69         /// Pointer to the InfAlg object
  70         const InfAlg *_ia;
  71
  72         /// Does all necessary preprocessing
  73         void init();
  74         /// Allocates space for \a _msgs
  75         void regenerateMessages();
  76         /// Allocates space for \a _beliefs
  77         void regenerateBeliefs();
  78
  79         /// Calculate all messages from InfAlg beliefs
  80         void calcMessages();
  81         /// Update factor->variable message (\a i -> \a I)
  82         void calcNewM(size_t i, size_t _I);
  83         /// Update variable->factor message (\a I -> \a i)
  84         void calcNewN(size_t i, size_t _I);
  85
  86         /// Calculate all variable and factor beliefs from messages
  87         void calcBeliefs();
  88         /// Calculate belief of variable \a i
  89         void calcBeliefV(size_t i);
  90         /// Calculate belief of factor \a I
  91         void calcBeliefF(size_t I);
  92
  93     public:
  94         /// Construct BP_dual object from (converged) InfAlg object's beliefs and factors.
  95         /** \warning A pointer to the the InfAlg object is stored,
  96          *  so the object must not be destroyed before the BP_dual is destroyed.
  97          */
  98         BP_dual( const InfAlg *ia ) : _ia(ia) { init(); }
  99
 100         /// Returns the underlying FactorGraph
 101         const FactorGraph& fg() const { return _ia->fg(); }
 102
 103         /// Returns reference to factor->variable message (\a I -> \a i)
 104         Prob & msgM( size_t i, size_t _I ) { return _msgs.m[i][_I]; }
 105         /// Returns constant reference to factor->variable message (\a I -> \a i)
 106         const Prob & msgM( size_t i, size_t _I ) const { return _msgs.m[i][_I]; }
 107         /// Returns reference to variable -> factor message (\a i -> \a I)
 108         Prob & msgN( size_t i, size_t _I ) { return _msgs.n[i][_I]; }
 109         /// Returns constant reference to variable -> factor message (\a i -> \a I)
 110         const Prob & msgN( size_t i, size_t _I ) const { return _msgs.n[i][_I]; }
 111         /// Returns reference to normalizer for factor->variable message (\a I -> \a i)
 112         Real & zM( size_t i, size_t _I ) { return _msgs.Zm[i][_I]; }
 113         /// Returns constant reference to normalizer for factor->variable message (\a I -> \a i)
 114         const Real & zM( size_t i, size_t _I ) const { return _msgs.Zm[i][_I]; }
 115         /// Returns reference to normalizer for variable -> factor message (\a i -> \a I)
 116         Real & zN( size_t i, size_t _I ) { return _msgs.Zn[i][_I]; }
 117         /// Returns constant reference to normalizer for variable -> factor message (\a i -> \a I)
 118         const Real & zN( size_t i, size_t _I ) const { return _msgs.Zn[i][_I]; }
 119
 120         /// Returns belief of variable \a i
 121         Factor beliefV( size_t i ) const { return Factor( _ia->fg().var(i), _beliefs.b1[i] ); }
 122         /// Returns belief of factor \a I
 123         Factor beliefF( size_t I ) const { return Factor( _ia->fg().factor(I).vars(), _beliefs.b2[I] ); }
 124
 125         /// Returns normalizer for belief of variable \a i
 126         Real beliefVZ( size_t i ) const { return _beliefs.Zb1[i]; }
 127         /// Returns normalizer for belief of factor \a I
 128         Real beliefFZ( size_t I ) const { return _beliefs.Zb2[I]; }
 129 };
 130
 131
 132 } // end of namespace dai
 133
 134
 135 #endif