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/********************* */
/*! \file inst_strategy_cegqi.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds, Mathias Preiner, Tim King
** This file is part of the CVC4 project.
** Copyright (c) 2009-2021 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 counterexample-guided quantifier instantiation
**/
#include "cvc4_private.h"
#ifndef CVC4__THEORY__QUANTIFIERS__INST_STRATEGY_CEGQI_H
#define CVC4__THEORY__QUANTIFIERS__INST_STRATEGY_CEGQI_H
#include "theory/decision_manager.h"
#include "theory/quantifiers/bv_inverter.h"
#include "theory/quantifiers/cegqi/ceg_instantiator.h"
#include "theory/quantifiers/cegqi/nested_qe.h"
#include "theory/quantifiers/cegqi/vts_term_cache.h"
#include "theory/quantifiers/instantiate.h"
#include "theory/quantifiers/quant_module.h"
#include "util/statistics_registry.h"
namespace CVC5 {
namespace theory {
namespace quantifiers {
class InstStrategyCegqi;
/**
* An instantiation rewriter based on the counterexample-guided instantiation
* quantifiers module below.
*/
class InstRewriterCegqi : public InstantiationRewriter
{
public:
InstRewriterCegqi(InstStrategyCegqi* p);
~InstRewriterCegqi() {}
/**
* Rewrite the instantiation via d_parent, based on virtual term substitution
* and nested quantifier elimination. Returns a TrustNode of kind REWRITE,
* corresponding to the rewrite and its proof generator.
*/
TrustNode rewriteInstantiation(Node q,
std::vector<Node>& terms,
Node inst,
bool doVts) override;
private:
/** pointer to the parent of this class */
InstStrategyCegqi* d_parent;
};
/**
* Counterexample-guided quantifier instantiation module.
*
* This class manages counterexample-guided instantiation strategies for all
* asserted quantified formulas.
*/
class InstStrategyCegqi : public QuantifiersModule
{
typedef context::CDHashSet<Node, NodeHashFunction> NodeSet;
typedef context::CDHashMap< Node, int, NodeHashFunction> NodeIntMap;
public:
InstStrategyCegqi(QuantifiersState& qs,
QuantifiersInferenceManager& qim,
QuantifiersRegistry& qr,
TermRegistry& tr);
~InstStrategyCegqi();
/** whether to do counterexample-guided instantiation for quantifier q */
bool doCbqi(Node q);
/** needs check at effort */
bool needsCheck(Theory::Effort e) override;
/** needs model at effort */
QEffort needsModel(Theory::Effort e) override;
/** reset round */
void reset_round(Theory::Effort e) override;
/** check */
void check(Theory::Effort e, QEffort quant_e) override;
/** check complete */
bool checkComplete() override;
/** check complete for quantified formula */
bool checkCompleteFor(Node q) override;
/** check ownership */
void checkOwnership(Node q) override;
/** identify */
std::string identify() const override { return std::string("Cegqi"); }
/** get instantiator for quantifier */
CegInstantiator* getInstantiator(Node q);
/** get the virtual term substitution term cache utility */
VtsTermCache* getVtsTermCache() const;
/** get the BV inverter utility */
BvInverter* getBvInverter() const;
/** pre-register quantifier */
void preRegisterQuantifier(Node q) override;
/**
* Rewrite the instantiation inst of quantified formula q for terms; return
* the result.
*
* We rewrite inst based on virtual term substitution and nested quantifier
* elimination. For details, see "Solving Quantified Linear Arithmetic via
* Counterexample-Guided Instantiation" FMSD 2017, Reynolds et al.
*
* Returns a TrustNode of kind REWRITE, corresponding to the rewrite and its
* proof generator.
*/
TrustNode rewriteInstantiation(Node q,
std::vector<Node>& terms,
Node inst,
bool doVts);
/** get the instantiation rewriter object */
InstantiationRewriter* getInstRewriter() const;
//------------------- interface for CegqiOutputInstStrategy
/** Instantiate the current quantified formula forall x. Q with x -> subs. */
bool doAddInstantiation(std::vector<Node>& subs);
//------------------- end interface for CegqiOutputInstStrategy
protected:
/** The instantiation rewriter object */
std::unique_ptr<InstRewriterCegqi> d_irew;
/** set quantified formula inactive
*
* This flag is set to true during a full effort check if at least one
* quantified formula is set "inactive", that is, its negation is
* unsatisfiable in the current context.
*/
bool d_cbqi_set_quant_inactive;
/** incomplete check
*
* This is set to true during a full effort check if this strategy could
* not find an instantiation for at least one asserted quantified formula.
*/
bool d_incomplete_check;
/** whether we have added cbqi lemma */
NodeSet d_added_cbqi_lemma;
/** parent guards */
std::map< Node, std::vector< Node > > d_parent_quant;
std::map< Node, std::vector< Node > > d_children_quant;
std::map< Node, bool > d_active_quant;
/** Whether cegqi handles each quantified formula. */
std::map<Node, CegHandledStatus> d_do_cbqi;
/**
* The instantiator for each quantified formula q registered to this class.
* This object is responsible for finding instantiatons for q.
*/
std::map<Node, std::unique_ptr<CegInstantiator>> d_cinst;
/** virtual term substitution term cache for arithmetic instantiation */
std::unique_ptr<VtsTermCache> d_vtsCache;
/** inversion utility for BV instantiation */
std::unique_ptr<BvInverter> d_bv_invert;
/**
* The decision strategy for each quantified formula q registered to this
* class.
*/
std::map<Node, std::unique_ptr<DecisionStrategy>> d_dstrat;
/** the current quantified formula we are processing */
Node d_curr_quant;
//---------------------- for vts delta minimization
/**
* Whether we will use vts delta minimization. If this flag is true, we
* add lemmas on demand of the form delta < c^1, delta < c^2, ... where c
* is a small (< 1) constant. This heuristic is used in strategies where
* vts delta cannot be fully eliminated from assertions (for example, when
* using nested quantifiers and a non-innermost instantiation strategy).
* The same strategy applies for vts infinity, which we add lemmas of the
* form inf > (1/c)^1, inf > (1/c)^2, ....
*/
bool d_check_vts_lemma_lc;
/** a small constant, used as a coefficient above */
Node d_small_const;
//---------------------- end for vts delta minimization
/** register ce lemma */
bool registerCbqiLemma( Node q );
/** register counterexample lemma
*
* This is called when we have constructed lem, the negation of the body of
* quantified formula q, skolemized with the instantiation constants of q.
* This function is used for setting up the proper information in the
* instantiator for q.
*/
void registerCounterexampleLemma(Node q, Node lem);
/** has added cbqi lemma */
bool hasAddedCbqiLemma( Node q ) { return d_added_cbqi_lemma.find( q )!=d_added_cbqi_lemma.end(); }
/**
* Return true if q can be processed with nested quantifier elimination.
* This may add a lemma on the output channel of quantifiers engine if so.
*
* @param q The quantified formula to process
* @param isPreregister Whether this method is being called at preregister.
*/
bool processNestedQe(Node q, bool isPreregister);
/** process functions */
void process(Node q, Theory::Effort effort, int e);
/**
* Get counterexample literal. This is the fresh Boolean variable whose
* semantics is "there exists a set of values for which the body of
* quantified formula q does not hold". These literals are cached by this
* class.
*/
Node getCounterexampleLiteral(Node q);
/** map from universal quantifiers to their counterexample literals */
std::map<Node, Node> d_ce_lit;
/** The nested quantifier elimination utility */
std::unique_ptr<NestedQe> d_nestedQe;
};
}
}
} // namespace CVC5
#endif
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