112 lines
4.1 KiB
C++
112 lines
4.1 KiB
C++
/*
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* AllDiff.cpp
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* @brief General "all-different" constraint
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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/AllDiff.h>
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#include <gtsam/base/Testable.h>
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#include <boost/make_shared.hpp>
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namespace gtsam {
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/* ************************************************************************* */
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AllDiff::AllDiff(const DiscreteKeys& dkeys) :
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Constraint(dkeys.indices()) {
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BOOST_FOREACH(const DiscreteKey& dkey, dkeys)
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cardinalities_.insert(dkey);
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}
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/* ************************************************************************* */
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void AllDiff::print(const std::string& s,
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const IndexFormatter& formatter) const {
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std::cout << s << "AllDiff on ";
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BOOST_FOREACH (Index dkey, keys_)
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std::cout << formatter(dkey) << " ";
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std::cout << std::endl;
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}
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/* ************************************************************************* */
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double AllDiff::operator()(const Values& values) const {
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std::set < size_t > taken; // record values taken by keys
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BOOST_FOREACH(Index dkey, keys_) {
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size_t value = values.at(dkey); // get the value for that key
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if (taken.count(value)) return 0.0;// check if value alreday taken
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taken.insert(value);// if not, record it as taken and keep checking
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}
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return 1.0;
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}
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/* ************************************************************************* */
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DecisionTreeFactor AllDiff::toDecisionTreeFactor() const {
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// We will do this by converting the allDif into many BinaryAllDiff constraints
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DecisionTreeFactor converted;
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size_t nrKeys = keys_.size();
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for (size_t i1 = 0; i1 < nrKeys; i1++)
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for (size_t i2 = i1 + 1; i2 < nrKeys; i2++) {
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BinaryAllDiff binary12(discreteKey(i1),discreteKey(i2));
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converted = converted * binary12.toDecisionTreeFactor();
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}
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return converted;
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}
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/* ************************************************************************* */
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DecisionTreeFactor AllDiff::operator*(const DecisionTreeFactor& f) const {
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// TODO: can we do this more efficiently?
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return toDecisionTreeFactor() * f;
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}
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/* ************************************************************************* */
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bool AllDiff::ensureArcConsistency(size_t j, std::vector<Domain>& domains) const {
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// Though strictly not part of allDiff, we check for
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// a value in domains[j] that does not occur in any other connected domain.
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// If found, we make this a singleton...
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// TODO: make a new constraint where this really is true
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Domain& Dj = domains[j];
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if (Dj.checkAllDiff(keys_, domains)) return true;
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// Check all other domains for singletons and erase corresponding values
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// This is the same as arc-consistency on the equivalent binary constraints
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bool changed = false;
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BOOST_FOREACH(Index k, keys_)
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if (k != j) {
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const Domain& Dk = domains[k];
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if (Dk.isSingleton()) { // check if singleton
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size_t value = Dk.firstValue();
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if (Dj.contains(value)) {
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Dj.erase(value); // erase value if true
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changed = true;
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}
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}
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}
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return changed;
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}
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/* ************************************************************************* */
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Constraint::shared_ptr AllDiff::partiallyApply(const Values& values) const {
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DiscreteKeys newKeys;
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// loop over keys and add them only if they do not appear in values
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BOOST_FOREACH(Index k, keys_)
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if (values.find(k) == values.end()) {
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newKeys.push_back(DiscreteKey(k,cardinalities_.at(k)));
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}
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return boost::make_shared<AllDiff>(newKeys);
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}
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/* ************************************************************************* */
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Constraint::shared_ptr AllDiff::partiallyApply(
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const std::vector<Domain>& domains) const {
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DiscreteFactor::Values known;
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BOOST_FOREACH(Index k, keys_) {
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const Domain& Dk = domains[k];
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if (Dk.isSingleton())
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known[k] = Dk.firstValue();
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}
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return partiallyApply(known);
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}
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/* ************************************************************************* */
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} // namespace gtsam
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