examples/example_varset.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) 2008-2009  Joris Mooij  [joris dot mooij at libdai dot org]
   8  */
   9
  10
  11 #include <dai/varset.h>
  12 #include <dai/index.h>
  13 #include <iostream>
  14
  15 using namespace std;
  16 using namespace dai;
  17
  18 int main() {
  19     Var x0(0, 2);   // Define binary variable x0 (with label 0)
  20     Var x1(1, 3);   // Define ternary variable x1 (with label 1)
  21
  22     // Define set X = {x0, x1}
  23     VarSet X; // empty
  24     X |= x1;  // X = {x1}
  25     X |= x0;  // X = {x1, x0}
  26     cout << "X = " << X << endl << endl; // Note that the elements of X are ordered according to their labels
  27
  28     // Output some information about x0, x1 and X
  29     cout << "Var " << x0 << " has " << x0.states() << " states (possible values)." << endl;
  30     cout << "Var " << x1 << " has " << x1.states() << " states." << endl << endl;
  31     cout << "VarSet " << X << " has " << X.nrStates() << " states (joint assignments of its variables)." << endl << endl;
  32
  33     cout << "States of VarSets correspond to states of their constituent Vars:" << endl;
  34     cout << "  state of x0:   state of x1:   (linear) state of X:" << endl;
  35     for( size_t s1 = 0; s1 < x1.states(); s1++ ) // for all states s1 of x1
  36         for( size_t s0 = 0; s0 < x0.states(); s0++ ) { // for all states s0 of x0
  37             // store s0 and s1 in a map "states"
  38             map<Var,size_t> states;
  39             states[x0] = s0;
  40             states[x1] = s1;
  41
  42             // output states of x0, x1 and corresponding state of X
  43             cout << "    " << s0 << "              " << s1 << "              " << X.calcState(states) << endl;
  44
  45             // VarSet::calcStates is the inverse of VarSet::calcState
  46             DAI_ASSERT( X.calcStates(X.calcState(states)) == states );
  47         }
  48
  49     cout << endl << "And vice versa:" << endl;
  50     cout << "  state of x0:   state of x1:   (linear) state of X:" << endl;
  51     for( size_t S = 0; S < X.nrStates(); S++ ) { // for all (joint) states of X
  52         // calculate states of x0 and x1 corresponding to state S of X
  53         map<Var,size_t> states = X.calcStates(S);
  54
  55         // output state of X and corresponding states of x0, x1
  56         cout << "    " << states[x0] << "              " << states[x1] << "              " << S << endl;
  57
  58         // VarSet::calcState is the inverse of VarSet::calcStates
  59         DAI_ASSERT( X.calcState(X.calcStates(S)) == S );
  60     }
  61
  62     cout << endl << "Iterating over all joint states using the State class:" << endl;
  63     cout << "  state of x0:   state of x1:   (linear) state of X:   state of X (as a map):" << endl;
  64     for( State S(X); S.valid(); S++ ) {
  65         // output state of X and corresponding states of x0, x1
  66         cout << "    " << S(x0) << "              " << S(x1) << "              " << S << "                      " << S.get() << endl;
  67     }
  68
  69     return 0;
  70 }