95 lines
2.7 KiB
C++
95 lines
2.7 KiB
C++
/*
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* CSP.cpp
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* @brief Constraint Satisfaction Problem class
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* @date Feb 6, 2012
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* @author Frank Dellaert
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*/
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#include <gtsam_unstable/discrete/Domain.h>
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#include <gtsam_unstable/discrete/CSP.h>
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#include <gtsam/discrete/DiscreteSequentialSolver.h>
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#include <gtsam/base/Testable.h>
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#include <boost/foreach.hpp>
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namespace gtsam {
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/// Find the best total assignment - can be expensive
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CSP::sharedValues CSP::optimalAssignment() const {
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DiscreteSequentialSolver solver(*this);
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DiscreteBayesNet::shared_ptr chordal = solver.eliminate();
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sharedValues mpe = optimize(*chordal);
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return mpe;
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}
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void CSP::runArcConsistency(size_t cardinality, size_t nrIterations, bool print) const {
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// Create VariableIndex
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VariableIndex index(*this);
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// index.print();
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size_t n = index.size();
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// Initialize domains
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std::vector < Domain > domains;
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for (size_t j = 0; j < n; j++)
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domains.push_back(Domain(DiscreteKey(j,cardinality)));
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// Create array of flags indicating a domain changed or not
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std::vector<bool> changed(n);
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// iterate nrIterations over entire grid
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for (size_t it = 0; it < nrIterations; it++) {
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bool anyChange = false;
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// iterate over all cells
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for (size_t v = 0; v < n; v++) {
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// keep track of which domains changed
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changed[v] = false;
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// loop over all factors/constraints for variable v
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const VariableIndex::Factors& factors = index[v];
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BOOST_FOREACH(size_t f,factors) {
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// if not already a singleton
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if (!domains[v].isSingleton()) {
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// get the constraint and call its ensureArcConsistency method
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Constraint::shared_ptr factor = (*this)[f];
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changed[v] = factor->ensureArcConsistency(v,domains) || changed[v];
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}
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} // f
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if (changed[v]) anyChange = true;
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} // v
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if (!anyChange) break;
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// TODO: Sudoku specific hack
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if (print) {
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if (cardinality == 9 && n == 81) {
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for (size_t i = 0, v = 0; i < sqrt(n); i++) {
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for (size_t j = 0; j < sqrt(n); j++, v++) {
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if (changed[v]) cout << "*";
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domains[v].print();
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cout << "\t";
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} // i
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cout << endl;
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} // j
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} else {
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for (size_t v = 0; v < n; v++) {
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if (changed[v]) cout << "*";
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domains[v].print();
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cout << "\t";
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} // v
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}
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cout << endl;
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} // print
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} // it
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#ifndef INPROGRESS
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// Now create new problem with all singleton variables removed
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// We do this by adding simplifying all factors using parial application
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// TODO: create a new ordering as we go, to ensure a connected graph
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// KeyOrdering ordering;
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// vector<Index> dkeys;
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BOOST_FOREACH(const Constraint::shared_ptr& factor, factors_) {
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Constraint::shared_ptr reduced = factor->partiallyApply(domains);
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if (print) reduced->print();
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}
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#endif
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}
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} // gtsam
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