gtsam/gtsam_unstable/discrete/Domain.h

/*
 * Domain.h
 * @brief Domain restriction constraint
 * @date Feb 13, 2012
 * @author Frank Dellaert
 */

#pragma once

#include <gtsam/discrete/DiscreteKey.h>
#include <gtsam_unstable/discrete/Constraint.h>
#include <optional>

namespace gtsam {

/**
 * The Domain class represents a constraint that restricts the possible values a
 * particular variable, with given key, can take on.
 */
class GTSAM_UNSTABLE_EXPORT Domain : public Constraint {
  size_t cardinality_;       /// Cardinality
  std::set<size_t> values_;  /// allowed values

 public:
  typedef std::shared_ptr<Domain> shared_ptr;

  // Constructor on Discrete Key initializes an "all-allowed" domain
  Domain(const DiscreteKey& dkey)
      : Constraint(dkey.first), cardinality_(dkey.second) {
    for (size_t v = 0; v < cardinality_; v++) values_.insert(v);
  }

  // Constructor on Discrete Key with single allowed value
  // Consider SingleValue constraint
  Domain(const DiscreteKey& dkey, size_t v)
      : Constraint(dkey.first), cardinality_(dkey.second) {
    values_.insert(v);
  }

  /// The one key
  Key key() const { return keys_[0]; }

  // The associated discrete key
  DiscreteKey discreteKey() const { return DiscreteKey(key(), cardinality_); }

  /// Insert a value, non const :-(
  void insert(size_t value) { values_.insert(value); }

  /// Erase a value, non const :-(
  void erase(size_t value) { values_.erase(value); }

  size_t nrValues() const { return values_.size(); }

  bool isSingleton() const { return nrValues() == 1; }

  size_t firstValue() const { return *values_.begin(); }

  // 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 Domain*>(&other))
      return false;
    else {
      const Domain& f(static_cast<const Domain&>(other));
      return (cardinality_ == f.cardinality_) && (values_ == f.values_);
    }
  }

  /// Compute error for each assignment and return as a tree
  AlgebraicDecisionTree<Key> errorTree() const override {
    throw std::runtime_error("Domain::error not implemented");
  }

  // Return concise string representation, mostly to debug arc consistency.
  // Converts from base 0 to base1.
  std::string base1Str() const;

  // Check whether domain cotains a specific value.
  bool contains(size_t value) const { return values_.count(value) > 0; }

  /// Calculate value
  double operator()(const DiscreteValues& values) const override;

  /// Convert into a decisiontree
  DecisionTreeFactor toDecisionTreeFactor() const override;

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

  /*
   * Ensure Arc-consistency by checking every possible value of domain j.
   * @param j domain to be checked
   * @param (in/out) domains all domains, but only domains->at(j) will be
   * checked.
   * @return true if domains->at(j) was changed, false otherwise.
   */
  bool ensureArcConsistency(Key j, Domains* domains) const override;

  /**
   * Check for a value in domain that does not occur in any other connected
   * domain. If found, return a a new singleton domain...
   * Called in AllDiff::ensureArcConsistency
   * @param keys connected domains through alldiff
   * @param keys other domains
   */
  std::optional<Domain> checkAllDiff(const KeyVector keys,
                                       const Domains& domains) const;

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

  /// Partially apply known values, domain version
  Constraint::shared_ptr partiallyApply(const Domains& domains) const override;
};

}  // namespace gtsam