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File:	src/theory/relevance_manager.h	Lines:	1	1	100.0 %
Date:	2021-09-10	Branches:	0	0	0.0 %


/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds
 *
 * This file is part of the cvc5 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.
 * ****************************************************************************
 *
 * Relevance manager.
 */

#include "cvc5_private.h"

#ifndef CVC5__THEORY__RELEVANCE_MANAGER__H
#define CVC5__THEORY__RELEVANCE_MANAGER__H

#include <unordered_map>
#include <unordered_set>

#include "context/cdlist.h"
#include "expr/node.h"
#include "theory/valuation.h"

namespace cvc5 {
namespace theory {

/**
 * This class manages queries related to relevance of asserted literals.
 * In particular, note the following definition:
 *
 * Let F be a formula, and let L = { l_1, ..., l_n } be a set of
 * literals that propositionally entail it. A "relevant selection of L with
 * respect to F" is a subset of L that also propositionally entails F.
 *
 * This class computes a relevant selection of the current assertion stack
 * at FULL effort with respect to the input formula + theory lemmas that are
 * critical to justify (see LemmaProperty::NEEDS_JUSTIFY). By default, theory
 * lemmas are not critical to justify; in fact, all T-valid theory lemmas
 * are not critical to justify, since they are guaranteed to be satisfied in
 * all inputs. However, some theory lemmas that introduce skolems need
 * justification.
 *
 * As an example of such a lemma, take the example input formula:
 *   (and (exists ((x Int)) (P x)) (not (P 0)))
 * A skolemization lemma like the following needs justification:
 *   (=> (exists ((x Int)) (P x)) (P k))
 * Intuitively, this is because the satisfiability of the existential above is
 * being deferred to the satisfiability of (P k) where k is fresh. Thus,
 * a relevant selection must include both (exists ((x Int)) (P x)) and (P k)
 * in this example.
 *
 * Theories are responsible for marking such lemmas using the NEEDS_JUSTIFY
 * property when calling OutputChannel::lemma.
 *
 * Notice that this class has some relation to the justification decision
 * heuristic (--decision=justification), which constructs a relevant selection
 * of the input formula by construction. This class is orthogonal to this
 * method, since it computes relevant selection *after* a full assignment. Thus
 * its main advantage with respect to decision=justification is that it can be
 * used in combination with any SAT decision heuristic.
 *
 * Internally, this class stores the input assertions and can be asked if an
 * asserted literal is part of the current relevant selection. The relevant
 * selection is computed lazily, i.e. only when someone asks if a literal is
 * relevant, and only at most once per FULL effort check.
 */
class RelevanceManager
{
  typedef context::CDList<Node> NodeList;

 public:
  RelevanceManager(context::UserContext* userContext, Valuation val);
  /**
   * Notify (preprocessed) assertions. This is called for input formulas or
   * lemmas that need justification that have been fully processed, just before
   * adding them to the PropEngine.
   */
  void notifyPreprocessedAssertions(const std::vector<Node>& assertions);
  /** Singleton version of above */
  void notifyPreprocessedAssertion(Node n);
  /**
   * Reset round, called at the beginning of a full effort check in
   * TheoryEngine.
   */
  void resetRound();
  /**
   * Is lit part of the current relevant selection? This computes the set of
   * relevant assertions if not already done so. This call is valid during a
   * full effort check in TheoryEngine, or after TheoryEngine has terminated
   * with "sat". This means that theories can query this during FULL or
   * LAST_CALL efforts, through the Valuation class.
   */
  bool isRelevant(Node lit);
  /**
   * Get the current relevant selection (see above). This computes this set
   * if not already done so. This call is valid during a full effort check in
   * TheoryEngine, or after TheoryEngine has terminated with "sat". This method
   * sets the flag success to false if we failed to compute relevant
   * assertions, which can occur if
   *
   * The value of this return is only valid if success was not updated to false.
   */
  const std::unordered_set<TNode>& getRelevantAssertions(bool& success);

 private:
  /**
   * Add the set of assertions to the formulas known to this class. This
   * method handles optimizations such as breaking apart top-level applications
   * of and.
   */
  void addAssertionsInternal(std::vector<Node>& toProcess);
  /** compute the relevant selection */
  void computeRelevance();
  /**
   * Justify formula n. To "justify" means we have added literals to our
   * relevant selection set (d_rset) whose current values ensure that n
   * evaluates to true or false.
   *
   * This method returns 1 if we justified n to be true, -1 means
   * justified n to be false, 0 means n could not be justified.
   */
  int justify(TNode n, std::unordered_map<TNode, int>& cache);
  /** Is the top symbol of cur a Boolean connective? */
  bool isBooleanConnective(TNode cur);
  /**
   * Update justify last child. This method is a helper function for justify,
   * which is called at the moment that Boolean connective formula cur
   * has a new child that has been computed in the justify cache.
   *
   * @param cur The Boolean connective formula
   * @param childrenJustify The values of the previous children (not including
   * the current one)
   * @param cache The justify cache
   * @return True if we wish to visit the next child. If this is the case, then
   * the justify value of the current child is added to childrenJustify.
   */
  bool updateJustifyLastChild(TNode cur,
                              std::vector<int>& childrenJustify,
                              std::unordered_map<TNode, int>& cache);
  /** The valuation object, used to query current value of theory literals */
  Valuation d_val;
  /** The input assertions */
  NodeList d_input;
  /** The current relevant selection. */
  std::unordered_set<TNode> d_rset;
  /** Have we computed the relevant selection this round? */
  bool d_computed;
  /**
   * Did we succeed in computing the relevant selection? If this is false, there
   * was a syncronization issue between the input formula and the satisfying
   * assignment since this class found that the input formula was not satisfied
   * by the assignment. This should never happen, but if it does, this class
   * aborts and indicates that all literals are relevant.
   */
  bool d_success;
};

}  // namespace theory
}  // namespace cvc5

#endif /* CVC5__THEORY__RELEVANCE_MANAGER__H */


Generated by: GCOVR (Version 3.2)

Line	Exec	Source
1		/******************************************************************************
2		* Top contributors (to current version):
3		* Andrew Reynolds
4		*
5		* This file is part of the cvc5 project.
6		*
7		* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
8		* in the top-level source directory and their institutional affiliations.
9		* All rights reserved. See the file COPYING in the top-level source
10		* directory for licensing information.
11		* ****************************************************************************
12		*
13		* Relevance manager.
14		*/
15
16		#include "cvc5_private.h"
17
18		#ifndef CVC5__THEORY__RELEVANCE_MANAGER__H
19		#define CVC5__THEORY__RELEVANCE_MANAGER__H
20
21		#include <unordered_map>
22		#include <unordered_set>
23
24		#include "context/cdlist.h"
25		#include "expr/node.h"
26		#include "theory/valuation.h"
27
28		namespace cvc5 {
29		namespace theory {
30
31		/**
32		* This class manages queries related to relevance of asserted literals.
33		* In particular, note the following definition:
34		*
35		* Let F be a formula, and let L = { l_1, ..., l_n } be a set of
36		* literals that propositionally entail it. A "relevant selection of L with
37		* respect to F" is a subset of L that also propositionally entails F.
38		*
39		* This class computes a relevant selection of the current assertion stack
40		* at FULL effort with respect to the input formula + theory lemmas that are
41		* critical to justify (see LemmaProperty::NEEDS_JUSTIFY). By default, theory
42		* lemmas are not critical to justify; in fact, all T-valid theory lemmas
43		* are not critical to justify, since they are guaranteed to be satisfied in
44		* all inputs. However, some theory lemmas that introduce skolems need
45		* justification.
46		*
47		* As an example of such a lemma, take the example input formula:
48		* (and (exists ((x Int)) (P x)) (not (P 0)))
49		* A skolemization lemma like the following needs justification:
50		* (=> (exists ((x Int)) (P x)) (P k))
51		* Intuitively, this is because the satisfiability of the existential above is
52		* being deferred to the satisfiability of (P k) where k is fresh. Thus,
53		* a relevant selection must include both (exists ((x Int)) (P x)) and (P k)
54		* in this example.
55		*
56		* Theories are responsible for marking such lemmas using the NEEDS_JUSTIFY
57		* property when calling OutputChannel::lemma.
58		*
59		* Notice that this class has some relation to the justification decision
60		* heuristic (--decision=justification), which constructs a relevant selection
61		* of the input formula by construction. This class is orthogonal to this
62		* method, since it computes relevant selection after a full assignment. Thus
63		* its main advantage with respect to decision=justification is that it can be
64		* used in combination with any SAT decision heuristic.
65		*
66		* Internally, this class stores the input assertions and can be asked if an
67		* asserted literal is part of the current relevant selection. The relevant
68		* selection is computed lazily, i.e. only when someone asks if a literal is
69		* relevant, and only at most once per FULL effort check.
70		*/
71	18	class RelevanceManager
72		{
73		typedef context::CDList<Node> NodeList;
74
75		public:
76		RelevanceManager(context::UserContext* userContext, Valuation val);
77		/**
78		* Notify (preprocessed) assertions. This is called for input formulas or
79		* lemmas that need justification that have been fully processed, just before
80		* adding them to the PropEngine.
81		*/
82		void notifyPreprocessedAssertions(const std::vector<Node>& assertions);
83		/** Singleton version of above */
84		void notifyPreprocessedAssertion(Node n);
85		/**
86		* Reset round, called at the beginning of a full effort check in
87		* TheoryEngine.
88		*/
89		void resetRound();
90		/**
91		* Is lit part of the current relevant selection? This computes the set of
92		* relevant assertions if not already done so. This call is valid during a
93		* full effort check in TheoryEngine, or after TheoryEngine has terminated
94		* with "sat". This means that theories can query this during FULL or
95		* LAST_CALL efforts, through the Valuation class.
96		*/
97		bool isRelevant(Node lit);
98		/**
99		* Get the current relevant selection (see above). This computes this set
100		* if not already done so. This call is valid during a full effort check in
101		* TheoryEngine, or after TheoryEngine has terminated with "sat". This method
102		* sets the flag success to false if we failed to compute relevant
103		* assertions, which can occur if
104		*
105		* The value of this return is only valid if success was not updated to false.
106		*/
107		const std::unordered_set<TNode>& getRelevantAssertions(bool& success);
108
109		private:
110		/**
111		* Add the set of assertions to the formulas known to this class. This
112		* method handles optimizations such as breaking apart top-level applications
113		* of and.
114		*/
115		void addAssertionsInternal(std::vector<Node>& toProcess);
116		/** compute the relevant selection */
117		void computeRelevance();
118		/**
119		* Justify formula n. To "justify" means we have added literals to our
120		* relevant selection set (d_rset) whose current values ensure that n
121		* evaluates to true or false.
122		*
123		* This method returns 1 if we justified n to be true, -1 means
124		* justified n to be false, 0 means n could not be justified.
125		*/
126		int justify(TNode n, std::unordered_map<TNode, int>& cache);
127		/** Is the top symbol of cur a Boolean connective? */
128		bool isBooleanConnective(TNode cur);
129		/**
130		* Update justify last child. This method is a helper function for justify,
131		* which is called at the moment that Boolean connective formula cur
132		* has a new child that has been computed in the justify cache.
133		*
134		* @param cur The Boolean connective formula
135		* @param childrenJustify The values of the previous children (not including
136		* the current one)
137		* @param cache The justify cache
138		* @return True if we wish to visit the next child. If this is the case, then
139		* the justify value of the current child is added to childrenJustify.
140		*/
141		bool updateJustifyLastChild(TNode cur,
142		std::vector<int>& childrenJustify,
143		std::unordered_map<TNode, int>& cache);
144		/** The valuation object, used to query current value of theory literals */
145		Valuation d_val;
146		/** The input assertions */
147		NodeList d_input;
148		/** The current relevant selection. */
149		std::unordered_set<TNode> d_rset;
150		/** Have we computed the relevant selection this round? */
151		bool d_computed;
152		/**
153		* Did we succeed in computing the relevant selection? If this is false, there
154		* was a syncronization issue between the input formula and the satisfying
155		* assignment since this class found that the input formula was not satisfied
156		* by the assignment. This should never happen, but if it does, this class
157		* aborts and indicates that all literals are relevant.
158		*/
159		bool d_success;
160		};
161
162		} // namespace theory
163		} // namespace cvc5
164
165		#endif /* CVC5__THEORY__RELEVANCE_MANAGER__H */