gtsam/gtsam_unstable/discrete/AllDiff.h

/*
 * AllDiff.h
 * @brief General "all-different" constraint
 * @date Feb 6, 2012
 * @author Frank Dellaert
 */

#pragma once

#include <gtsam/discrete/DiscreteKey.h>
#include <gtsam_unstable/discrete/BinaryAllDiff.h>

namespace gtsam {

/**
 * General AllDiff constraint
 * Returns 1 if values for all keys are different, 0 otherwise
 * DiscreteFactors are all awkward in that they have to store two types of keys:
 * for each variable we have a Key and an Key. In this factor, we
 * keep the Indices locally, and the Indices are stored in IndexFactor.
 */
class GTSAM_UNSTABLE_EXPORT AllDiff : public Constraint {
  std::map<Key, size_t> cardinalities_;

  DiscreteKey discreteKey(size_t i) const {
    Key j = keys_[i];
    return DiscreteKey(j, cardinalities_.at(j));
  }

 public:
  /// Constructor
  AllDiff(const DiscreteKeys& dkeys);

  // print
  void print(const std::string& s = "", const KeyFormatter& formatter =
                                            DefaultKeyFormatter) const override;

  /// equals
  bool equals(const DiscreteFactor& other, double tol) const override {
    if (!dynamic_cast<const AllDiff*>(&other))
      return false;
    else {
      const AllDiff& f(static_cast<const AllDiff&>(other));
      return cardinalities_.size() == f.cardinalities_.size() &&
             std::equal(cardinalities_.begin(), cardinalities_.end(),
                        f.cardinalities_.begin());
    }
  }

  /// Calculate value = expensive !
  double operator()(const Values& values) const override;

  /// Convert into a decisiontree, can be *very* expensive !
  DecisionTreeFactor toDecisionTreeFactor() const override;

  /// Multiply into a decisiontree
  DecisionTreeFactor operator*(const DecisionTreeFactor& f) const override;

  /*
   * Ensure Arc-consistency
   * Arc-consistency involves creating binaryAllDiff constraints
   * In which case the combinatorial hyper-arc explosion disappears.
   * @param j domain to be checked
   * @param domains all other domains
   */
  bool ensureArcConsistency(size_t j,
                            std::vector<Domain>& domains) const override;

  /// Partially apply known values
  Constraint::shared_ptr partiallyApply(const Values&) const override;

  /// Partially apply known values, domain version
  Constraint::shared_ptr partiallyApply(
      const std::vector<Domain>&) const override;
};

}  // namespace gtsam