78 lines
2.6 KiB
C++
78 lines
2.6 KiB
C++
/*
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* CSP.h
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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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#pragma once
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#include <gtsam/discrete/DiscreteFactorGraph.h>
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#include <gtsam_unstable/discrete/AllDiff.h>
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#include <gtsam_unstable/discrete/SingleValue.h>
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namespace gtsam {
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/**
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* Constraint Satisfaction Problem class
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* A specialization of a DiscreteFactorGraph.
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* It knows about CSP-specific constraints and algorithms
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*/
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class GTSAM_UNSTABLE_EXPORT CSP : public DiscreteFactorGraph {
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public:
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/** A map from keys to values */
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typedef Assignment<Key> Values;
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typedef boost::shared_ptr<Values> sharedValues;
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public:
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/// Add a unary constraint, allowing only a single value
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void addSingleValue(const DiscreteKey& dkey, size_t value) {
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emplace_shared<SingleValue>(dkey, value);
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}
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/// Add a binary AllDiff constraint
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void addAllDiff(const DiscreteKey& key1, const DiscreteKey& key2) {
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emplace_shared<BinaryAllDiff>(key1, key2);
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}
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/// Add a general AllDiff constraint
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void addAllDiff(const DiscreteKeys& dkeys) { emplace_shared<AllDiff>(dkeys); }
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// /** return product of all factors as a single factor */
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// DecisionTreeFactor product() const {
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// DecisionTreeFactor result;
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// for(const sharedFactor& factor: *this)
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// if (factor) result = (*factor) * result;
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// return result;
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// }
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/// Find the best total assignment - can be expensive.
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sharedValues optimalAssignment() const;
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/// Find the best total assignment, with given ordering - can be expensive.
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sharedValues optimalAssignment(const Ordering& ordering) const;
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// /*
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// * Perform loopy belief propagation
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// * True belief propagation would check for each value in domain
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// * whether any satisfying separator assignment can be found.
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// * This corresponds to hyper-arc consistency in CSP speak.
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// * This can be done by creating a mini-factor graph and search.
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// * For a nine-by-nine Sudoku, the search tree will be 8+6+6=20 levels
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// deep.
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// * It will be very expensive to exclude values that way.
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// */
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// void applyBeliefPropagation(size_t nrIterations = 10) const;
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/*
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* Apply arc-consistency ~ Approximate loopy belief propagation
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* We need to give the domains to a constraint, and it returns
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* a domain whose values don't conflict in the arc-consistency way.
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* TODO: should get cardinality from DiscreteKeys
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*/
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void runArcConsistency(size_t cardinality, size_t nrIterations = 10,
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bool print = false) const;
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}; // CSP
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} // namespace gtsam
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