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/********************* */
/*! \file trigger.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds, Morgan Deters, 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 trigger class
**/
#include "cvc4_private.h"
#ifndef CVC4__THEORY__QUANTIFIERS__TRIGGER_H
#define CVC4__THEORY__QUANTIFIERS__TRIGGER_H
#include "expr/node.h"
#include "theory/inference_id.h"
namespace cvc5 {
namespace theory {
class QuantifiersEngine;
class Valuation;
namespace quantifiers {
class QuantifiersState;
class QuantifiersInferenceManager;
class QuantifiersRegistry;
class TermRegistry;
class InstMatch;
namespace inst {
class IMGenerator;
class InstMatchGenerator;
/** A collection of nodes representing a trigger.
*
* This class encapsulates all implementations of E-matching in CVC4.
* Its primary use is as a utility of the quantifiers module InstantiationEngine
* (see theory/quantifiers/ematching/instantiation_engine.h) which uses Trigger to make
* appropriate calls to Instantiate::addInstantiation(...)
* (see theory/instantiate.h) for the instantiate utility of the quantifiers
* engine (d_quantEngine) associated with this trigger. These calls
* queue instantiation lemmas to the output channel of TheoryQuantifiers during
* a full effort check.
*
* Concretely, a Trigger* t is used in the following way during a full effort
* check. Assume that t is associated with quantified formula q (see field d_f).
* We call :
*
* // setup initial information
* t->resetInstantiationRound();
* // will produce instantiations based on matching with all terms
* t->reset( Node::null() );
* // add all instantiations based on E-matching with this trigger and the
* // current context
* t->addInstantiations();
*
* This will result in (a set of) calls to
* Instantiate::addInstantiation(q, m1)...Instantiate::addInstantiation(q, mn),
* where m1...mn are InstMatch objects. These calls add the corresponding
* instantiation lemma for (q,mi) on the output channel associated with
* d_quantEngine.
*
* The Trigger class is wrapper around an underlying IMGenerator class, which
* implements various forms of E-matching for its set of nodes (d_nodes), which
* is refered to in the literature as a "trigger". A trigger is a set of terms
* whose free variables are the bound variables of a quantified formula q,
* and that is used to guide instantiations for q (for example, see "Efficient
* E-Matching for SMT Solvers" by de Moura et al).
*
* For example of an instantiation lemma produced by E-matching :
*
* quantified formula : forall x. P( x )
* trigger : P( x )
* ground context : ~P( a )
*
* Then E-matching matches P( x ) and P( a ), resulting in the match { x -> a }
* which is used to generate the instantiation lemma :
* (forall x. P( x )) => P( a )
*
* Terms that are provided as input to a Trigger class via mkTrigger
* should be in "instantiation constant form", see TermUtil::getInstConstantNode.
* Say we have quantified formula q whose AST is the Node
* (FORALL
* (BOUND_VAR_LIST x)
* (NOT (P x))
* (INST_PATTERN_LIST (INST_PATTERN (P x))))
* then TermUtil::getInstConstantNode( q, (P x) ) = (P IC) where
* IC = TermUtil::getInstantiationConstant( q, i ).
* Trigger expects as input (P IC) to represent the Trigger (P x). This form
* ensures that references to bound variables are unique to quantified formulas,
* which is required to ensure the correctness of instantiation lemmas we
* generate.
*
*/
class Trigger {
friend class IMGenerator;
public:
/** trigger constructor */
Trigger(QuantifiersState& qs,
QuantifiersInferenceManager& qim,
QuantifiersRegistry& qr,
TermRegistry& tr,
Node q,
std::vector<Node>& nodes);
virtual ~Trigger();
/** get the generator associated with this trigger */
IMGenerator* getGenerator() { return d_mg; }
/** Reset instantiation round.
*
* Called once at beginning of an instantiation round.
*/
void resetInstantiationRound();
/** Reset the trigger.
*
* eqc is the equivalence class from which to match ground terms. If eqc is
* Node::null(), then we match ground terms from all equivalence classes.
*/
void reset( Node eqc );
/** add all available instantiations, based on the current context
*
* This function makes the appropriate calls to d_qe->addInstantiation(...)
* based on the current ground terms and equalities in the current context,
* via queries to functions in d_qe. This calls the addInstantiations function
* of the underlying match generator. It can be extended to
* produce instantiations beyond what is produced by the match generator
* (for example, see theory/quantifiers/ematching/ho_trigger.h).
*/
virtual uint64_t addInstantiations();
/** Return whether this is a multi-trigger. */
bool isMultiTrigger() const;
/** Get instantiation pattern list associated with this trigger.
*
* An instantiation pattern list is the node representation of a trigger, in
* particular, it is the third argument of quantified formulas which have user
* (! ... :pattern) attributes.
*/
Node getInstPattern() const;
/* A heuristic value indicating how active this generator is.
*
* This returns the number of ground terms for the match operators in terms
* from d_nodes. This score is only used with the experimental option
* --trigger-active-sel.
*/
int getActiveScore();
/** print debug information for the trigger */
void debugPrint(const char* c) const;
protected:
/** add an instantiation (called by InstMatchGenerator)
*
* This calls Instantiate::addInstantiation(...) for instantiations
* associated with m. Typically, m is associated with a single instantiation,
* but in some cases (e.g. higher-order) we may modify m before calling
* Instantiate::addInstantiation(...).
*/
virtual bool sendInstantiation(std::vector<Node>& m, InferenceId id);
/** inst match version, calls the above method */
bool sendInstantiation(InstMatch& m, InferenceId id);
/**
* Ensure that all ground subterms of n have been preprocessed. This makes
* calls to the provided valuation to obtain the preprocessed form of these
* terms. The preprocessed form of each ground subterm is added to gts.
*
* As an optimization, this method does not preprocess terms with no
* arguments, e.g. variables and constants are not preprocessed (as they
* should not change after preprocessing), nor are they added to gts.
*
* @param val The valuation to use for looking up preprocessed terms.
* @param n The node to process, which is in inst-constant form (free
* variables have been substituted by corresponding INST_CONSTANT).
* @param gts The set of preprocessed ground subterms of n.
* @return The converted form of n where all ground subterms have been
* replaced by their preprocessed form.
*/
static Node ensureGroundTermPreprocessed(Valuation& val,
Node n,
std::vector<Node>& gts);
/** The nodes comprising this trigger. */
std::vector<Node> d_nodes;
/**
* The preprocessed ground terms in the nodes of the trigger, which as an
* optimization omits variables and constant subterms. These terms are
* important since we must ensure that the quantifier-free solvers are
* aware of these terms. In particular, when adding instantiations for
* a trigger P(f(a), x), we first check if f(a) is a term in the master
* equality engine. If it is not, then we add the lemma k = f(a) where k
* is the purification skolem for f(a). This ensures that f(a) will be
* registered as a term in the master equality engine on the next
* instantiation round. This is particularly important for cases where
* P(f(a), x) is matched with P(f(b), c), where a=b in the current context.
* This example would fail to match when f(a) is not registered.
*/
std::vector<Node> d_groundTerms;
/** Reference to the quantifiers state */
QuantifiersState& d_qstate;
/** Reference to the quantifiers inference manager */
QuantifiersInferenceManager& d_qim;
/** The quantifiers registry */
QuantifiersRegistry& d_qreg;
/** Reference to the term registry */
TermRegistry& d_treg;
/** The quantified formula this trigger is for. */
Node d_quant;
/** match generator
*
* This is the back-end utility that implements the underlying matching
* algorithm associated with this trigger.
*/
IMGenerator* d_mg;
}; /* class Trigger */
} // namespace inst
} // namespace quantifiers
} // namespace theory
} // namespace cvc5
#endif /* CVC4__THEORY__QUANTIFIERS__TRIGGER_H */
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