src/factor.cpp

   1 /*  This file is part of libDAI - http://www.libdai.org/
   2  *
   3  *  libDAI is licensed under the terms of the GNU General Public License version
   4  *  2, or (at your option) any later version. libDAI is distributed without any
   5  *  warranty. See the file COPYING for more details.
   6  *
   7  *  Copyright (C) 2006-2010  Joris Mooij  [joris dot mooij at libdai dot org]
   8  *  Copyright (C) 2006-2007  Radboud University Nijmegen, The Netherlands
   9  */
  10
  11
  12 #include <dai/factor.h>
  13
  14
  15 namespace dai {
  16
  17
  18 using namespace std;
  19
  20
  21 Factor createFactorIsing( const Var &n, Real h ) {
  22     DAI_ASSERT( n.states() == 2 );
  23     Real buf[2];
  24     buf[0] = std::exp(-h);
  25     buf[1] = std::exp(h);
  26     return Factor(n, &buf[0]);
  27 }
  28
  29
  30 Factor createFactorIsing( const Var &n1, const Var &n2, Real J ) {
  31     DAI_ASSERT( n1.states() == 2 );
  32     DAI_ASSERT( n2.states() == 2 );
  33     DAI_ASSERT( n1 != n2 );
  34     Real buf[4];
  35     buf[0] = (buf[3] = std::exp(J));
  36     buf[1] = (buf[2] = std::exp(-J));
  37     return Factor( VarSet(n1, n2), &buf[0] );
  38 }
  39
  40
  41 Factor createFactorExpGauss( const VarSet &ns, Real beta ) {
  42     Factor fac( ns );
  43     for( size_t t = 0; t < fac.nrStates(); t++ )
  44         fac.set( t, std::exp(rnd_stdnormal() * beta) );
  45     return fac;
  46 }
  47
  48
  49 Factor createFactorPotts( const Var &n1, const Var &n2, Real J ) {
  50     Factor fac( VarSet( n1, n2 ), 1.0 );
  51     DAI_ASSERT( n1.states() == n2.states() );
  52     for( size_t s = 0; s < n1.states(); s++ )
  53         fac.set( s * (n1.states() + 1), std::exp(J) );
  54     return fac;
  55 }
  56
  57
  58 Factor createFactorDelta( const Var &v, size_t state ) {
  59     Factor fac( v, 0.0 );
  60     DAI_ASSERT( state < v.states() );
  61     fac.set( state, 1.0 );
  62     return fac;
  63 }
  64
  65
  66 Factor createFactorDelta( const VarSet& vs, size_t state ) {
  67     Factor fac( vs, 0.0 );
  68     DAI_ASSERT( state < vs.nrStates() );
  69     fac.set( state, 1.0 );
  70     return fac;
  71 }
  72
  73
  74 } // end of namespace dai