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/********************* */
/*! \file proof_equality_engine.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2019 by the authors listed in the file AUTHORS
** in the top-level source directory) and their institutional affiliations.
** All rights reserved. See the file COPYING in the top-level source
** directory for licensing information.\endverbatim
**
** \brief The proof-producing equality engine
**/
#include "cvc4_private.h"
#ifndef CVC4__THEORY__UF__PROOF_EQUALITY_ENGINE_H
#define CVC4__THEORY__UF__PROOF_EQUALITY_ENGINE_H
#include <map>
#include <vector>
#include "context/cdhashmap.h"
#include "expr/lazy_proof.h"
#include "expr/node.h"
#include "expr/proof_node.h"
#include "expr/proof_node_manager.h"
#include "expr/proof_step_buffer.h"
#include "theory/eager_proof_generator.h"
#include "theory/uf/equality_engine.h"
namespace CVC4 {
namespace theory {
namespace eq {
/**
* A layer on top of an EqualityEngine. The goal of this class is manage the
* use of an EqualityEngine object in such a way that the proper proofs are
* internally constructed, and can be retrieved from this class when
* necessary.
*
* It tracks the reason for why all facts are added to an EqualityEngine in a
* SAT-context dependent manner in a context-dependent (CDProof) object.
*
* It is an eager proof generator (see theory/proof_generator.h), in that
* it stores (copies) of proofs for lemmas at the moment they are sent out.
*
* A theory that is proof producing and uses the equality engine may use this
* class to manage proofs that are justified by its underlying equality engine.
*/
class ProofEqEngine : public EagerProofGenerator
{
typedef context::CDHashSet<Node, NodeHashFunction> NodeSet;
typedef context::CDHashMap<Node, std::shared_ptr<ProofNode>, NodeHashFunction>
NodeProofMap;
public:
ProofEqEngine(context::Context* c,
context::UserContext* u,
EqualityEngine& ee,
ProofNodeManager* pnm,
bool pfEnabled = true,
bool recExplain = false);
~ProofEqEngine() {}
//-------------------------- assert assumption
/** Assert predicate lit by assumption */
bool assertAssume(TNode lit);
//-------------------------- assert fact
/**
* Assert the predicate lit by proof step id, given explanation exp and
* arguments args.
*/
bool assertFact(Node lit,
PfRule id,
const std::vector<Node>& exp,
const std::vector<Node>& args);
bool assertFact(Node lit, PfRule id, Node exp, const std::vector<Node>& args);
/** Multi-step versions */
bool assertFact(Node lit, Node exp, ProofStepBuffer& psb);
bool assertFact(Node lit, Node exp, ProofGenerator* pg);
//-------------------------- assert conflicts
/**
* This method is called when the equality engine of this class is
* inconsistent (false has been proven) by a contradictory literal lit. This
* returns the trust node corresponding to the current conflict.
*/
TrustNode assertConflict(Node lit);
/**
* Get proven conflict from contradictory facts. This method is called when
* the proof rule with premises exp and arguments args implies a contradiction
* by proof rule id.
*
* This method returns the TrustNode containing the corresponding conflict
* resulting from adding this step, and ensures that a proof has been stored
* internally so that this class may respond to a call to
* ProofGenerator::getProof(...).
*/
TrustNode assertConflict(PfRule id,
const std::vector<Node>& exp,
const std::vector<Node>& args);
/** Multi-step version */
TrustNode assertConflict(const std::vector<Node>& exp, ProofStepBuffer& psb);
// TrustNode assertConflict(ProofNode* p);
//-------------------------- assert lemma
/**
* Called when we have concluded conc, which is either false or a
* disjunction.
*
* We provide the explanation in two parts:
* (1) exp \ noExplain, which are literals that hold in the equality engine of
* this class,
* (2) noExplain, which do not necessarily hold in the equality engine of this
* class.
* Notice that noExplain is a subset of exp.
*
* The proof for conc follows from exp ^ expn by proof rule with the given
* id and arguments.
*
* This call corresponds to a lemma if conc is false and expn is empty.
*
* This returns the TrustNode corresponding to the formula corresonding to
* the call to this method [*], for which a proof can be provided by this
* generator in the remainder of the user context.
*
* [*]
* a. If this call does not correspond to a conflict, then this formula is:
* ( ^_{e in exp} <explain>(e) ^ expn ) => conc
* where <explain>(e) is a conjunction of literals L1 ^ ... ^ Ln such that
* L1 ^ ... ^ Ln entail e, and each Li was passed as an argument to
* assertAssume(...) in the current SAT context. This explanation method
* always succeeds, provided that e is a literal that currently holds in
* the equality engine of this class. Notice that if the antecedant is empty,
* the formula above is assumed to be conc itself. The above formula is
* intended to be valid in Theory that owns this class.
* b. If this call is a conflict, then this formula is:
* ^_{e in exp} <explain>(e)
* The above formula is intended to be equivalent to false according to the
* Theory that owns this class.
*/
TrustNode assertLemma(Node conc,
PfRule id,
const std::vector<Node>& exp,
const std::vector<Node>& noExplain,
const std::vector<Node>& args);
/** Multi-step version */
TrustNode assertLemma(Node conc,
const std::vector<Node>& exp,
const std::vector<Node>& noExplain,
ProofStepBuffer& psb);
/** Generator version */
TrustNode assertLemma(Node conc,
const std::vector<Node>& exp,
const std::vector<Node>& noExplain,
ProofGenerator* pg);
//-------------------------- explain
TrustNode explain(Node conc);
/** identify */
std::string identify() const override;
protected:
/** Add proof step */
bool addProofStep(Node lit,
PfRule id,
const std::vector<Node>& exp,
const std::vector<Node>& args);
/** Assert internal */
bool assertFactInternal(TNode pred, bool polarity, TNode reason);
/** assert lemma internal */
TrustNode assertLemmaInternal(Node conc,
const std::vector<Node>& exp,
const std::vector<Node>& noExplain,
LazyCDProof* curr);
/** ensure proof for fact */
TrustNode ensureProofForFact(Node conc,
const std::vector<TNode>& assumps,
TrustNodeKind tnk,
LazyCDProof* curr);
/**
* Make the conjunction of nodes in a. Returns true if a is empty, and a
* single literal if a has size 1.
*/
Node mkAnd(const std::vector<Node>& a);
Node mkAnd(const std::vector<TNode>& a);
/** flatten and, returns the conjuncts to a */
void flattenAnd(TNode an, std::vector<Node>& a);
private:
/** Reference to the equality engine */
eq::EqualityEngine& d_ee;
/** common nodes */
Node d_true;
Node d_false;
/** the proof node manager */
ProofNodeManager* d_pnm;
/** The SAT-context-dependent proof object */
LazyCDProof d_proof;
/**
* The keep set of this class. This set is maintained to ensure that
* facts and their explanations are reference counted. Since facts and their
* explanations are SAT-context-dependent, this set is also
* SAT-context-dependent.
*/
NodeSet d_keep;
/**
* Whether proofs are enabled. If this flag is false, then this class acts
* as a simplified interface to the EqualityEngine, without proofs.
*/
bool d_pfEnabled;
/**
* Recurse explanations
*/
bool d_recExplain;
/** Explain
*
* This adds to assumps the set of facts that were asserted to this
* class in the current SAT context by calls to assertAssume that are
* required for showing lit.
*
* This additionally registers the equality proof steps required to
* regress the explanation of lit.
*/
void explainWithProof(Node lit,
std::vector<TNode>& assumps,
LazyCDProof* curr);
};
} // namespace eq
} // namespace theory
} // namespace CVC4
#endif /* CVC4__THEORY__STRINGS__PROOF_MANAGER_H */
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