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       1                 :            : /******************************************************************************
       2                 :            :  * Top contributors (to current version):
       3                 :            :  *   Alex Ozdemir, Tim King, Andrew Reynolds
       4                 :            :  *
       5                 :            :  * This file is part of the cvc5 project.
       6                 :            :  *
       7                 :            :  * Copyright (c) 2009-2025 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                 :            :  * Congruence manager, the interface to the equality engine from the
      14                 :            :  * linear arithmetic solver
      15                 :            :  */
      16                 :            : 
      17                 :            : #include "cvc5_private.h"
      18                 :            : 
      19                 :            : #pragma once
      20                 :            : 
      21                 :            : #include "context/cdhashmap.h"
      22                 :            : #include "context/cdlist.h"
      23                 :            : #include "context/cdmaybe.h"
      24                 :            : #include "context/cdtrail_queue.h"
      25                 :            : #include "proof/trust_node.h"
      26                 :            : #include "smt/env_obj.h"
      27                 :            : #include "theory/arith/arith_utilities.h"
      28                 :            : #include "theory/arith/linear/arithvar.h"
      29                 :            : #include "theory/arith/linear/arithvar_node_map.h"
      30                 :            : #include "theory/arith/linear/callbacks.h"
      31                 :            : #include "theory/arith/linear/constraint_forward.h"
      32                 :            : #include "theory/uf/equality_engine_notify.h"
      33                 :            : #include "util/dense_map.h"
      34                 :            : #include "util/statistics_stats.h"
      35                 :            : 
      36                 :            : namespace cvc5::internal {
      37                 :            : 
      38                 :            : class ProofNodeManager;
      39                 :            : class EagerProofGenerator;
      40                 :            : 
      41                 :            : namespace theory {
      42                 :            : 
      43                 :            : namespace eq {
      44                 :            : class ProofEqEngine;
      45                 :            : class EqualityEngine;
      46                 :            : }
      47                 :            : 
      48                 :            : namespace arith::linear {
      49                 :            : 
      50                 :            : class ArithVariables;
      51                 :            : 
      52                 :            : class ArithCongruenceManager : protected EnvObj
      53                 :            : {
      54                 :            :  public:
      55                 :            :   ArithCongruenceManager(Env& env,
      56                 :            :                          ConstraintDatabase&,
      57                 :            :                          SetupLiteralCallBack,
      58                 :            :                          const ArithVariables&,
      59                 :            :                          RaiseEqualityEngineConflict raiseConflict);
      60                 :            :   ~ArithCongruenceManager();
      61                 :            : 
      62                 :            :   //--------------------------------- initialization
      63                 :            :   /**
      64                 :            :    * Finish initialize. This class is instructed by TheoryArithPrivate to use
      65                 :            :    * the equality engine ee.
      66                 :            :    */
      67                 :            :   void finishInit(eq::EqualityEngine* ee);
      68                 :            :   //--------------------------------- end initialization
      69                 :            : 
      70                 :            :   /**
      71                 :            :    * Return the trust node for the explanation of literal. The returned
      72                 :            :    * trust node is generated by the proof equality engine of this class.
      73                 :            :    */
      74                 :            :   TrustNode explain(TNode literal);
      75                 :            : 
      76                 :            :   void addWatchedPair(ArithVar s, TNode x, TNode y);
      77                 :            : 
      78                 :   12773200 :   bool isWatchedVariable(ArithVar s) const
      79                 :            :   {
      80                 :   12773200 :     return d_watchedVariables.isMember(s);
      81                 :            :   }
      82                 :            : 
      83                 :            :   /** Assert an equality. */
      84                 :            :   void watchedVariableIsZero(ConstraintCP eq);
      85                 :            : 
      86                 :            :   /** Assert a conjunction from lb and ub. */
      87                 :            :   void watchedVariableIsZero(ConstraintCP lb, ConstraintCP ub);
      88                 :            : 
      89                 :            :   /** Assert that the value cannot be zero. */
      90                 :            :   void watchedVariableCannotBeZero(ConstraintCP c);
      91                 :            : 
      92                 :            :   /** Assert that the value cannot be zero. */
      93                 :            :   void watchedVariableCannotBeZero(ConstraintCP c, ConstraintCP d);
      94                 :            : 
      95                 :            :   /** Assert that the value is congruent to a constant. */
      96                 :            :   void equalsConstant(ConstraintCP eq);
      97                 :            :   void equalsConstant(ConstraintCP lb, ConstraintCP ub);
      98                 :            : 
      99                 :            :   bool inConflict() const;
     100                 :            : 
     101                 :            :   bool hasMorePropagations() const;
     102                 :            : 
     103                 :            :   const Node getNextPropagation();
     104                 :            : 
     105                 :            :   bool canExplain(TNode n) const;
     106                 :            : 
     107                 :            :   /**
     108                 :            :    * Propagate. Called when the equality engine has inferred literal x.
     109                 :            :    */
     110                 :            :   bool propagate(TNode x);
     111                 :            : 
     112                 :            :  private:
     113                 :            :   context::CDRaised d_inConflict;
     114                 :            :   RaiseEqualityEngineConflict d_raiseConflict;
     115                 :            : 
     116                 :            :   /**
     117                 :            :    * The set of ArithVars equivalent to a pair of terms.
     118                 :            :    * If this is 0 or cannot be 0, this can be signalled.
     119                 :            :    * The pair of terms for the congruence is stored in watched equalities.
     120                 :            :    */
     121                 :            :   DenseSet d_watchedVariables;
     122                 :            :   /** d_watchedVariables |-> (= x y) */
     123                 :            :   ArithVarToNodeMap d_watchedEqualities;
     124                 :            : 
     125                 :            :   context::CDList<Node> d_keepAlive;
     126                 :            : 
     127                 :            :   /** Store the propagations. */
     128                 :            :   context::CDTrailQueue<Node> d_propagatations;
     129                 :            : 
     130                 :            :   /* This maps the node a theory engine will request on an explain call to
     131                 :            :    * to its corresponding PropUnit.
     132                 :            :    * This is node is potentially both the propagation or
     133                 :            :    * rewrite(propagation).
     134                 :            :    */
     135                 :            :   using ExplainMap = context::CDHashMap<Node, size_t>;
     136                 :            :   ExplainMap d_explanationMap;
     137                 :            : 
     138                 :            :   ConstraintDatabase& d_constraintDatabase;
     139                 :            :   SetupLiteralCallBack d_setupLiteral;
     140                 :            : 
     141                 :            :   const ArithVariables& d_avariables;
     142                 :            : 
     143                 :            :   /** The equality engine being used by this class */
     144                 :            :   eq::EqualityEngine* d_ee;
     145                 :            :   /** proof manager */
     146                 :            :   ProofNodeManager* d_pnm;
     147                 :            :   /** A proof generator for storing proofs of facts that are asserted to the EQ
     148                 :            :    * engine. Note that these proofs **are not closed**; they may contain
     149                 :            :    * literals from the explanation of their fact as unclosed assumptions.
     150                 :            :    * This makes these proofs SAT-context depdent.
     151                 :            :    *
     152                 :            :    * This is why this generator is separate from the TheoryArithPrivate
     153                 :            :    * generator, which stores closed proofs.
     154                 :            :    */
     155                 :            :   std::unique_ptr<EagerProofGenerator> d_pfGenEe;
     156                 :            :   /** A proof generator for TrustNodes sent to TheoryArithPrivate.
     157                 :            :    *
     158                 :            :    * When TheoryArithPrivate requests an explanation from
     159                 :            :    * ArithCongruenceManager, it can request a TrustNode for that explanation.
     160                 :            :    * This proof generator is the one used in that TrustNode: it stores the
     161                 :            :    * (closed) proofs of implications proved by the
     162                 :            :    * ArithCongruenceManager/EqualityEngine.
     163                 :            :    *
     164                 :            :    * It is insufficient to just use the ProofGenerator from the ProofEqEngine,
     165                 :            :    * since sometimes the ArithCongruenceManager needs to add some
     166                 :            :    * arith-specific reasoning to extend the proof (e.g. rewriting the result
     167                 :            :    * into a normal form).
     168                 :            :    * */
     169                 :            :   std::unique_ptr<EagerProofGenerator> d_pfGenExplain;
     170                 :            : 
     171                 :            :   /** Pointer to the proof equality engine of TheoryArith */
     172                 :            :   theory::eq::ProofEqEngine* d_pfee;
     173                 :            : 
     174                 :            :   /** Raise a conflict node `conflict` to the theory of arithmetic.
     175                 :            :    *
     176                 :            :    * When proofs are enabled, a (closed) proof of the conflict should be
     177                 :            :    * provided.
     178                 :            :    */
     179                 :            :   void raiseConflict(Node conflict, std::shared_ptr<ProofNode> pf = nullptr);
     180                 :            :   /**
     181                 :            :    * Are proofs enabled? This is true if a non-null proof manager was provided
     182                 :            :    * to the constructor of this class.
     183                 :            :    */
     184                 :            :   bool isProofEnabled() const;
     185                 :            : 
     186                 :            :   Node externalToInternal(TNode n) const;
     187                 :            : 
     188                 :            :   void pushBack(TNode n);
     189                 :            : 
     190                 :            :   void pushBack(TNode n, TNode r);
     191                 :            : 
     192                 :            :   void pushBack(TNode n, TNode r, TNode w);
     193                 :            : 
     194                 :            :   /** Assert this literal to the eq engine. Common functionality for
     195                 :            :    *   * assertionToEqualityEngine(..)
     196                 :            :    *   * equalsConstant(c)
     197                 :            :    *   * equalsConstant(lb, ub)
     198                 :            :    * If proof is off, then just asserts.
     199                 :            :    */
     200                 :            :   void assertLitToEqualityEngine(Node lit,
     201                 :            :                                  TNode reason,
     202                 :            :                                  std::shared_ptr<ProofNode> pf);
     203                 :            :   /** This sends a shared term to the uninterpreted equality engine. */
     204                 :            :   void assertionToEqualityEngine(bool eq,
     205                 :            :                                  ArithVar s,
     206                 :            :                                  TNode reason,
     207                 :            :                                  std::shared_ptr<ProofNode> pf);
     208                 :            : 
     209                 :            :   /** Check for proof for this or a symmetric fact
     210                 :            :    *
     211                 :            :    * The proof submitted to this method are stored in `d_pfGenEe`, and should
     212                 :            :    * have closure properties consistent with the documentation for that member.
     213                 :            :    *
     214                 :            :    * @returns whether this or a symmetric fact has a proof.
     215                 :            :    */
     216                 :            :   bool hasProofFor(TNode f) const;
     217                 :            :   /**
     218                 :            :    * Sets the proof for this fact and the symmetric one.
     219                 :            :    *
     220                 :            :    * The proof submitted to this method are stored in `d_pfGenEe`, and should
     221                 :            :    * have closure properties consistent with the documentation for that member.
     222                 :            :    * */
     223                 :            :   void setProofFor(TNode f, std::shared_ptr<ProofNode> pf) const;
     224                 :            : 
     225                 :            :   /** Dequeues the delay queue and asserts these equalities.*/
     226                 :            :   void enableSharedTerms();
     227                 :            :   void dequeueLiterals();
     228                 :            : 
     229                 :            :   /**
     230                 :            :    * Determine an explaination for `internal`. That is a conjunction of theory
     231                 :            :    * literals which imply `internal`.
     232                 :            :    *
     233                 :            :    * The TrustNode here is a trusted propagation.
     234                 :            :    */
     235                 :            :   TrustNode explainInternal(TNode internal);
     236                 :            : 
     237                 :            :   class Statistics {
     238                 :            :   public:
     239                 :            :     IntStat d_watchedVariables;
     240                 :            :     IntStat d_watchedVariableIsZero;
     241                 :            :     IntStat d_watchedVariableIsNotZero;
     242                 :            : 
     243                 :            :     IntStat d_equalsConstantCalls;
     244                 :            : 
     245                 :            :     IntStat d_propagations;
     246                 :            :     IntStat d_propagateConstraints;
     247                 :            :     IntStat d_conflicts;
     248                 :            : 
     249                 :            :     Statistics(StatisticsRegistry& sr);
     250                 :            :   } d_statistics;
     251                 :            : 
     252                 :            : }; /* class ArithCongruenceManager */
     253                 :            : 
     254                 :            : }  // namespace arith
     255                 :            : }  // namespace theory
     256                 :            : }  // namespace cvc5::internal