src/theory/theory_engine.h

   1 /*********************                                                        */
   2 /*! \file theory_engine.h
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Dejan Jovanovic, Morgan Deters, Andrew Reynolds
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2019 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.\endverbatim
  11  **
  12  ** \brief The theory engine
  13  **
  14  ** The theory engine.
  15  **/
  16
  17 #include "cvc4_private.h"
  18
  19 #ifndef CVC4__THEORY_ENGINE_H
  20 #define CVC4__THEORY_ENGINE_H
  21
  22 #include <deque>
  23 #include <memory>
  24 #include <set>
  25 #include <unordered_map>
  26 #include <vector>
  27 #include <utility>
  28
  29 #include "base/cvc4_assert.h"
  30 #include "context/cdhashset.h"
  31 #include "expr/node.h"
  32 #include "options/options.h"
  33 #include "options/smt_options.h"
  34 #include "prop/prop_engine.h"
  35 #include "smt/command.h"
  36 #include "smt_util/lemma_channels.h"
  37 #include "theory/atom_requests.h"
  38 #include "theory/decision_manager.h"
  39 #include "theory/interrupted.h"
  40 #include "theory/rewriter.h"
  41 #include "theory/shared_terms_database.h"
  42 #include "theory/sort_inference.h"
  43 #include "theory/substitutions.h"
  44 #include "theory/term_registration_visitor.h"
  45 #include "theory/theory.h"
  46 #include "theory/uf/equality_engine.h"
  47 #include "theory/valuation.h"
  48 #include "util/hash.h"
  49 #include "util/statistics_registry.h"
  50 #include "util/unsafe_interrupt_exception.h"
  51
  52 namespace CVC4 {
  53
  54 class ResourceManager;
  55 class LemmaProofRecipe;
  56
  57 /**
  58  * A pair of a theory and a node. This is used to mark the flow of
  59  * propagations between theories.
  60  */
  61 struct NodeTheoryPair {
  62   Node node;
  63   theory::TheoryId theory;
  64   size_t timestamp;
  65   NodeTheoryPair(TNode node, theory::TheoryId theory, size_t timestamp = 0)
  66   : node(node), theory(theory), timestamp(timestamp) {}
  67   NodeTheoryPair() : theory(theory::THEORY_LAST), timestamp() {}
  68   // Comparison doesn't take into account the timestamp
  69   bool operator == (const NodeTheoryPair& pair) const {
  70     return node == pair.node && theory == pair.theory;
  71   }
  72 };/* struct NodeTheoryPair */
  73
  74 struct NodeTheoryPairHashFunction {
  75   NodeHashFunction hashFunction;
  76   // Hash doesn't take into account the timestamp
  77   size_t operator()(const NodeTheoryPair& pair) const {
  78     uint64_t hash = fnv1a::fnv1a_64(NodeHashFunction()(pair.node));
  79     return static_cast<size_t>(fnv1a::fnv1a_64(pair.theory, hash));
  80   }
  81 };/* struct NodeTheoryPairHashFunction */
  82
  83
  84 /* Forward declarations */
  85 namespace theory {
  86   class TheoryModel;
  87   class TheoryEngineModelBuilder;
  88
  89   namespace eq {
  90     class EqualityEngine;
  91   }/* CVC4::theory::eq namespace */
  92
  93   namespace quantifiers {
  94     class TermDb;
  95   }
  96
  97   class EntailmentCheckParameters;
  98   class EntailmentCheckSideEffects;
  99 }/* CVC4::theory namespace */
 100
 101 class DecisionEngine;
 102 class RemoveTermFormulas;
 103
 104 /**
 105  * This is essentially an abstraction for a collection of theories.  A
 106  * TheoryEngine provides services to a PropEngine, making various
 107  * T-solvers look like a single unit to the propositional part of
 108  * CVC4.
 109  */
 110 class TheoryEngine {
 111
 112   /** Shared terms database can use the internals notify the theories */
 113   friend class SharedTermsDatabase;
 114   friend class theory::quantifiers::TermDb;
 115
 116   /** Associated PropEngine engine */
 117   prop::PropEngine* d_propEngine;
 118
 119   /** Access to decision engine */
 120   DecisionEngine* d_decisionEngine;
 121
 122   /** Our context */
 123   context::Context* d_context;
 124
 125   /** Our user context */
 126   context::UserContext* d_userContext;
 127
 128   /**
 129    * A table of from theory IDs to theory pointers. Never use this table
 130    * directly, use theoryOf() instead.
 131    */
 132   theory::Theory* d_theoryTable[theory::THEORY_LAST];
 133
 134   /**
 135    * A collection of theories that are "active" for the current run.
 136    * This set is provided by the user (as a logic string, say, in SMT-LIBv2
 137    * format input), or else by default it's all-inclusive.  This is important
 138    * because we can optimize for single-theory runs (no sharing), can reduce
 139    * the cost of walking the DAG on registration, etc.
 140    */
 141   const LogicInfo& d_logicInfo;
 142
 143   /**
 144    * The database of shared terms.
 145    */
 146   SharedTermsDatabase d_sharedTerms;
 147
 148   /**
 149    * Master equality engine, to share with theories.
 150    */
 151   theory::eq::EqualityEngine* d_masterEqualityEngine;
 152
 153   /** notify class for master equality engine */
 154   class NotifyClass : public theory::eq::EqualityEngineNotify {
 155     TheoryEngine& d_te;
 156   public:
 157     NotifyClass(TheoryEngine& te): d_te(te) {}
 158     bool eqNotifyTriggerEquality(TNode equality, bool value) override
 159     {
 160       return true;
 161     }
 162     bool eqNotifyTriggerPredicate(TNode predicate, bool value) override
 163     {
 164       return true;
 165     }
 166     bool eqNotifyTriggerTermEquality(theory::TheoryId tag,
 167                                      TNode t1,
 168                                      TNode t2,
 169                                      bool value) override
 170     {
 171       return true;
 172     }
 173     void eqNotifyConstantTermMerge(TNode t1, TNode t2) override {}
 174     void eqNotifyNewClass(TNode t) override { d_te.eqNotifyNewClass(t); }
 175     void eqNotifyPreMerge(TNode t1, TNode t2) override
 176     {
 177       d_te.eqNotifyPreMerge(t1, t2);
 178     }
 179     void eqNotifyPostMerge(TNode t1, TNode t2) override
 180     {
 181       d_te.eqNotifyPostMerge(t1, t2);
 182     }
 183     void eqNotifyDisequal(TNode t1, TNode t2, TNode reason) override
 184     {
 185       d_te.eqNotifyDisequal(t1, t2, reason);
 186     }
 187   };/* class TheoryEngine::NotifyClass */
 188   NotifyClass d_masterEENotify;
 189
 190   /**
 191    * notification methods
 192    */
 193   void eqNotifyNewClass(TNode t);
 194   void eqNotifyPreMerge(TNode t1, TNode t2);
 195   void eqNotifyPostMerge(TNode t1, TNode t2);
 196   void eqNotifyDisequal(TNode t1, TNode t2, TNode reason);
 197
 198   /**
 199    * The quantifiers engine
 200    */
 201   theory::QuantifiersEngine* d_quantEngine;
 202   /**
 203    * The decision manager
 204    */
 205   std::unique_ptr<theory::DecisionManager> d_decManager;
 206
 207   /**
 208    * Default model object
 209    */
 210   theory::TheoryModel* d_curr_model;
 211   bool d_aloc_curr_model;
 212   /**
 213    * Model builder object
 214    */
 215   theory::TheoryEngineModelBuilder* d_curr_model_builder;
 216   bool d_aloc_curr_model_builder;
 217   /** are we in eager model building mode? (see setEagerModelBuilding). */
 218   bool d_eager_model_building;
 219
 220   typedef std::unordered_map<Node, Node, NodeHashFunction> NodeMap;
 221   typedef std::unordered_map<TNode, Node, TNodeHashFunction> TNodeMap;
 222
 223   /**
 224   * Cache for theory-preprocessing of assertions
 225    */
 226   NodeMap d_ppCache;
 227
 228   /**
 229    * Used for "missed-t-propagations" dumping mode only.  A set of all
 230    * theory-propagable literals.
 231    */
 232   context::CDList<TNode> d_possiblePropagations;
 233
 234   /**
 235    * Used for "missed-t-propagations" dumping mode only.  A
 236    * context-dependent set of those theory-propagable literals that
 237    * have been propagated.
 238    */
 239   context::CDHashSet<Node, NodeHashFunction> d_hasPropagated;
 240
 241
 242   /**
 243    * Statistics for a particular theory.
 244    */
 245   class Statistics {
 246
 247     static std::string mkName(std::string prefix,
 248                               theory::TheoryId theory,
 249                               std::string suffix) {
 250       std::stringstream ss;
 251       ss << prefix << theory << suffix;
 252       return ss.str();
 253     }
 254
 255    public:
 256     IntStat conflicts, propagations, lemmas, requirePhase, restartDemands;
 257
 258     Statistics(theory::TheoryId theory);
 259     ~Statistics();
 260   };/* class TheoryEngine::Statistics */
 261
 262   /**
 263    * An output channel for Theory that passes messages
 264    * back to a TheoryEngine.
 265    */
 266   class EngineOutputChannel : public theory::OutputChannel {
 267     friend class TheoryEngine;
 268
 269     /**
 270      * The theory engine we're communicating with.
 271      */
 272     TheoryEngine* d_engine;
 273
 274     /**
 275      * The statistics of the theory interractions.
 276      */
 277     Statistics d_statistics;
 278
 279     /** The theory owning this channel. */
 280     theory::TheoryId d_theory;
 281
 282    public:
 283     EngineOutputChannel(TheoryEngine* engine, theory::TheoryId theory)
 284         : d_engine(engine), d_statistics(theory), d_theory(theory) {}
 285
 286     void safePoint(uint64_t amount) override {
 287       spendResource(amount);
 288       if (d_engine->d_interrupted) {
 289         throw theory::Interrupted();
 290       }
 291     }
 292
 293     void conflict(TNode conflictNode,
 294                   std::unique_ptr<Proof> pf = nullptr) override;
 295     bool propagate(TNode literal) override;
 296
 297     theory::LemmaStatus lemma(TNode lemma, ProofRule rule,
 298                               bool removable = false, bool preprocess = false,
 299                               bool sendAtoms = false) override;
 300
 301     theory::LemmaStatus splitLemma(TNode lemma,
 302                                    bool removable = false) override;
 303
 304     void demandRestart() override {
 305       NodeManager* curr = NodeManager::currentNM();
 306       Node restartVar = curr->mkSkolem(
 307           "restartVar", curr->booleanType(),
 308           "A boolean variable asserted to be true to force a restart");
 309       Trace("theory::restart")
 310           << "EngineOutputChannel<" << d_theory << ">::restart(" << restartVar
 311           << ")" << std::endl;
 312       ++d_statistics.restartDemands;
 313       lemma(restartVar, RULE_INVALID, true);
 314     }
 315
 316     void requirePhase(TNode n, bool phase) override {
 317       Debug("theory") << "EngineOutputChannel::requirePhase(" << n << ", "
 318                       << phase << ")" << std::endl;
 319       ++d_statistics.requirePhase;
 320       d_engine->d_propEngine->requirePhase(n, phase);
 321     }
 322
 323     void setIncomplete() override {
 324       Trace("theory") << "TheoryEngine::setIncomplete()" << std::endl;
 325       d_engine->setIncomplete(d_theory);
 326     }
 327
 328     void spendResource(unsigned amount) override {
 329       d_engine->spendResource(amount);
 330     }
 331
 332     void handleUserAttribute(const char* attr, theory::Theory* t) override {
 333       d_engine->handleUserAttribute(attr, t);
 334     }
 335
 336    private:
 337     /**
 338      * A helper function for registering lemma recipes with the proof engine
 339      */
 340     void registerLemmaRecipe(Node lemma, Node originalLemma, bool preprocess,
 341                              theory::TheoryId theoryId);
 342   }; /* class TheoryEngine::EngineOutputChannel */
 343
 344   /**
 345    * Output channels for individual theories.
 346    */
 347   EngineOutputChannel* d_theoryOut[theory::THEORY_LAST];
 348
 349   /**
 350    * Are we in conflict.
 351    */
 352   context::CDO<bool> d_inConflict;
 353
 354   /**
 355    * Are we in "SAT mode"? In this state, the user can query for the model.
 356    * This corresponds to the state in Figure 4.1, page 52 of the SMT-LIB
 357    * standard, version 2.6.
 358    */
 359   bool d_inSatMode;
 360
 361   /**
 362    * Called by the theories to notify of a conflict.
 363    */
 364   void conflict(TNode conflict, theory::TheoryId theoryId);
 365
 366   /**
 367    * Debugging flag to ensure that shutdown() is called before the
 368    * destructor.
 369    */
 370   bool d_hasShutDown;
 371
 372   /**
 373    * True if a theory has notified us of incompleteness (at this
 374    * context level or below).
 375    */
 376   context::CDO<bool> d_incomplete;
 377
 378   /**
 379    * Called by the theories to notify that the current branch is incomplete.
 380    */
 381   void setIncomplete(theory::TheoryId theory) {
 382     d_incomplete = true;
 383   }
 384
 385
 386   /**
 387    * Mapping of propagations from recievers to senders.
 388    */
 389   typedef context::CDHashMap<NodeTheoryPair, NodeTheoryPair, NodeTheoryPairHashFunction> PropagationMap;
 390   PropagationMap d_propagationMap;
 391
 392   /**
 393    * Timestamp of propagations
 394    */
 395   context::CDO<size_t> d_propagationMapTimestamp;
 396
 397   /**
 398    * Literals that are propagated by the theory. Note that these are TNodes.
 399    * The theory can only propagate nodes that have an assigned literal in the
 400    * SAT solver and are hence referenced in the SAT solver.
 401    */
 402   context::CDList<TNode> d_propagatedLiterals;
 403
 404   /**
 405    * The index of the next literal to be propagated by a theory.
 406    */
 407   context::CDO<unsigned> d_propagatedLiteralsIndex;
 408
 409   /**
 410    * Called by the output channel to propagate literals and facts
 411    * @return false if immediate conflict
 412    */
 413   bool propagate(TNode literal, theory::TheoryId theory);
 414
 415   /**
 416    * Internal method to call the propagation routines and collect the
 417    * propagated literals.
 418    */
 419   void propagate(theory::Theory::Effort effort);
 420
 421   /**
 422    * A variable to mark if we added any lemmas.
 423    */
 424   bool d_lemmasAdded;
 425
 426   /**
 427    * A variable to mark if the OutputChannel was "used" by any theory
 428    * since the start of the last check.  If it has been, we require
 429    * a FULL_EFFORT check before exiting and reporting SAT.
 430    *
 431    * See the documentation for the needCheck() function, below.
 432    */
 433   bool d_outputChannelUsed;
 434
 435   /** Atom requests from lemmas */
 436   AtomRequests d_atomRequests;
 437
 438   /**
 439    * Adds a new lemma, returning its status.
 440    * @param node the lemma
 441    * @param negated should the lemma be asserted negated
 442    * @param removable can the lemma be remove (restrictions apply)
 443    * @param needAtoms if not THEORY_LAST, then
 444    */
 445   theory::LemmaStatus lemma(TNode node,
 446                             ProofRule rule,
 447                             bool negated,
 448                             bool removable,
 449                             bool preprocess,
 450                             theory::TheoryId atomsTo);
 451
 452   /** Enusre that the given atoms are send to the given theory */
 453   void ensureLemmaAtoms(const std::vector<TNode>& atoms, theory::TheoryId theory);
 454
 455   RemoveTermFormulas& d_tform_remover;
 456
 457   /** sort inference module */
 458   SortInference d_sortInfer;
 459
 460   /** Time spent in theory combination */
 461   TimerStat d_combineTheoriesTime;
 462
 463   Node d_true;
 464   Node d_false;
 465
 466   /** Whether we were just interrupted (or not) */
 467   bool d_interrupted;
 468   ResourceManager* d_resourceManager;
 469
 470   /** Container for lemma input and output channels. */
 471   LemmaChannels* d_channels;
 472
 473 public:
 474
 475   /** Constructs a theory engine */
 476   TheoryEngine(context::Context* context, context::UserContext* userContext,
 477                RemoveTermFormulas& iteRemover, const LogicInfo& logic,
 478                LemmaChannels* channels);
 479
 480   /** Destroys a theory engine */
 481   ~TheoryEngine();
 482
 483   void interrupt();
 484
 485   /** "Spend" a resource during a search or preprocessing.*/
 486   void spendResource(unsigned amount);
 487
 488   /**
 489    * Adds a theory. Only one theory per TheoryId can be present, so if
 490    * there is another theory it will be deleted.
 491    */
 492   template <class TheoryClass>
 493   inline void addTheory(theory::TheoryId theoryId) {
 494     Assert(d_theoryTable[theoryId] == NULL && d_theoryOut[theoryId] == NULL);
 495     d_theoryOut[theoryId] = new EngineOutputChannel(this, theoryId);
 496     d_theoryTable[theoryId] =
 497         new TheoryClass(d_context, d_userContext, *d_theoryOut[theoryId],
 498                         theory::Valuation(this), d_logicInfo);
 499   }
 500
 501   inline void setPropEngine(prop::PropEngine* propEngine) {
 502     Assert(d_propEngine == NULL);
 503     d_propEngine = propEngine;
 504   }
 505
 506   inline void setDecisionEngine(DecisionEngine* decisionEngine) {
 507     Assert(d_decisionEngine == NULL);
 508     d_decisionEngine = decisionEngine;
 509   }
 510
 511   /** Called when all initialization of options/logic is done */
 512   void finishInit();
 513
 514   /**
 515    * Get a pointer to the underlying propositional engine.
 516    */
 517   inline prop::PropEngine* getPropEngine() const {
 518     return d_propEngine;
 519   }
 520
 521   /**
 522    * Get a pointer to the underlying sat context.
 523    */
 524   inline context::Context* getSatContext() const {
 525     return d_context;
 526   }
 527
 528   /**
 529    * Get a pointer to the underlying user context.
 530    */
 531   inline context::Context* getUserContext() const {
 532     return d_userContext;
 533   }
 534
 535   /**
 536    * Get a pointer to the underlying quantifiers engine.
 537    */
 538   theory::QuantifiersEngine* getQuantifiersEngine() const {
 539     return d_quantEngine;
 540   }
 541   /**
 542    * Get a pointer to the underlying decision manager.
 543    */
 544   theory::DecisionManager* getDecisionManager() const
 545   {
 546     return d_decManager.get();
 547   }
 548
 549  private:
 550   /**
 551    * Helper for preprocess
 552    */
 553   Node ppTheoryRewrite(TNode term);
 554
 555   /**
 556    * Queue of nodes for pre-registration.
 557    */
 558   std::queue<TNode> d_preregisterQueue;
 559
 560   /**
 561    * Boolean flag denoting we are in pre-registration.
 562    */
 563   bool d_inPreregister;
 564
 565   /**
 566    * Did the theories get any new facts since the last time we called
 567    * check()
 568    */
 569   context::CDO<bool> d_factsAsserted;
 570
 571   /**
 572    * Map from equality atoms to theories that would like to be notified about them.
 573    */
 574
 575
 576   /**
 577    * Assert the formula to the given theory.
 578    * @param assertion the assertion to send (not necesserily normalized)
 579    * @param original the assertion as it was sent in from the propagating theory
 580    * @param toTheoryId the theory to assert to
 581    * @param fromTheoryId the theory that sent it
 582    */
 583   void assertToTheory(TNode assertion, TNode originalAssertion, theory::TheoryId toTheoryId, theory::TheoryId fromTheoryId);
 584
 585   /**
 586    * Marks a theory propagation from a theory to a theory where a
 587    * theory could be the THEORY_SAT_SOLVER for literals coming from
 588    * or being propagated to the SAT solver. If the receiving theory
 589    * already recieved the literal, the method returns false, otherwise
 590    * it returns true.
 591    *
 592    * @param assertion the normalized assertion being sent
 593    * @param originalAssertion the actual assertion that was sent
 594    * @param toTheoryId the theory that is on the receiving end
 595    * @param fromTheoryId the theory that sent the assertino
 596    * @return true if a new assertion, false if theory already got it
 597    */
 598   bool markPropagation(TNode assertion, TNode originalAssertions, theory::TheoryId toTheoryId, theory::TheoryId fromTheoryId);
 599
 600   /**
 601    * Computes the explanation by travarsing the propagation graph and
 602    * asking relevant theories to explain the propagations. Initially
 603    * the explanation vector should contain only the element (node, theory)
 604    * where the node is the one to be explained, and the theory is the
 605    * theory that sent the literal. The lemmaProofRecipe will contain a list
 606    * of the explanation steps required to produce the original node.
 607    */
 608   void getExplanation(std::vector<NodeTheoryPair>& explanationVector, LemmaProofRecipe* lemmaProofRecipe);
 609
 610 public:
 611
 612   /**
 613    * Signal the start of a new round of assertion preprocessing
 614    */
 615   void preprocessStart();
 616
 617   /**
 618    * Runs theory specific preprocessing on the non-Boolean parts of
 619    * the formula.  This is only called on input assertions, after ITEs
 620    * have been removed.
 621    */
 622   Node preprocess(TNode node);
 623
 624   /** Notify (preprocessed) assertions. */
 625   void notifyPreprocessedAssertions(const std::vector<Node>& assertions);
 626
 627   /** Return whether or not we are incomplete (in the current context). */
 628   inline bool isIncomplete() const { return d_incomplete; }
 629
 630   /**
 631    * Returns true if we need another round of checking.  If this
 632    * returns true, check(FULL_EFFORT) _must_ be called by the
 633    * propositional layer before reporting SAT.
 634    *
 635    * This is especially necessary for incomplete theories that lazily
 636    * output some lemmas on FULL_EFFORT check (e.g. quantifier reasoning
 637    * outputing quantifier instantiations).  In such a case, a lemma can
 638    * be asserted that is simplified away (perhaps it's already true).
 639    * However, we must maintain the invariant that, if a theory uses the
 640    * OutputChannel, it implicitly requests that another check(FULL_EFFORT)
 641    * be performed before exit, even if no new facts are on its fact queue,
 642    * as it might decide to further instantiate some lemmas, precluding
 643    * a SAT response.
 644    */
 645   inline bool needCheck() const {
 646     return d_outputChannelUsed || d_lemmasAdded;
 647   }
 648
 649   /**
 650    * This is called at shutdown time by the SmtEngine, just before
 651    * destruction.  It is important because there are destruction
 652    * ordering issues between PropEngine and Theory.
 653    */
 654   void shutdown();
 655
 656   /**
 657    * Solve the given literal with a theory that owns it.
 658    */
 659   theory::Theory::PPAssertStatus solve(TNode literal,
 660                                     theory::SubstitutionMap& substitutionOut);
 661
 662   /**
 663    * Preregister a Theory atom with the responsible theory (or
 664    * theories).
 665    */
 666   void preRegister(TNode preprocessed);
 667
 668   /**
 669    * Assert the formula to the appropriate theory.
 670    * @param node the assertion
 671    */
 672   void assertFact(TNode node);
 673
 674   /**
 675    * Check all (currently-active) theories for conflicts.
 676    * @param effort the effort level to use
 677    */
 678   void check(theory::Theory::Effort effort);
 679
 680   /**
 681    * Run the combination framework.
 682    */
 683   void combineTheories();
 684
 685   /**
 686    * Calls ppStaticLearn() on all theories, accumulating their
 687    * combined contributions in the "learned" builder.
 688    */
 689   void ppStaticLearn(TNode in, NodeBuilder<>& learned);
 690
 691   /**
 692    * Calls presolve() on all theories and returns true
 693    * if one of the theories discovers a conflict.
 694    */
 695   bool presolve();
 696
 697    /**
 698    * Calls postsolve() on all theories.
 699    */
 700   void postsolve();
 701
 702   /**
 703    * Calls notifyRestart() on all active theories.
 704    */
 705   void notifyRestart();
 706
 707   void getPropagatedLiterals(std::vector<TNode>& literals) {
 708     for (; d_propagatedLiteralsIndex < d_propagatedLiterals.size(); d_propagatedLiteralsIndex = d_propagatedLiteralsIndex + 1) {
 709       Debug("getPropagatedLiterals") << "TheoryEngine::getPropagatedLiterals: propagating: " << d_propagatedLiterals[d_propagatedLiteralsIndex] << std::endl;
 710       literals.push_back(d_propagatedLiterals[d_propagatedLiteralsIndex]);
 711     }
 712   }
 713
 714   /**
 715    * Returns the next decision request, or null if none exist. The next
 716    * decision request is a literal that this theory engine prefers the SAT
 717    * solver to make as its next decision. Decision requests are managed by
 718    * the decision manager d_decManager.
 719    */
 720   Node getNextDecisionRequest();
 721
 722   bool properConflict(TNode conflict) const;
 723   bool properPropagation(TNode lit) const;
 724   bool properExplanation(TNode node, TNode expl) const;
 725
 726   /**
 727    * Returns an explanation of the node propagated to the SAT solver.
 728    */
 729   Node getExplanation(TNode node);
 730
 731   /**
 732    * Returns an explanation of the node propagated to the SAT solver and the theory
 733    * that propagated it.
 734    */
 735   Node getExplanationAndRecipe(TNode node, LemmaProofRecipe* proofRecipe);
 736
 737   /**
 738    * collect model info
 739    */
 740   bool collectModelInfo(theory::TheoryModel* m);
 741   /** post process model */
 742   void postProcessModel( theory::TheoryModel* m );
 743
 744   /**
 745    * Get the pointer to the model object used by this theory engine.
 746    */
 747   theory::TheoryModel* getModel();
 748   /**
 749    * Get the current model for the current set of assertions. This method
 750    * should only be called immediately after a satisfiable or unknown
 751    * response to a check-sat call, and only if produceModels is true.
 752    *
 753    * If the model is not already built, this will cause this theory engine
 754    * to build the model.
 755    *
 756    * If the model is not available (for instance, if the last call to check-sat
 757    * was interrupted), then this returns the null pointer.
 758    */
 759   theory::TheoryModel* getBuiltModel();
 760   /** set eager model building
 761    *
 762    * If this method is called, then this TheoryEngine will henceforth build
 763    * its model immediately after every satisfiability check that results
 764    * in a satisfiable or unknown result. The motivation for this mode is to
 765    * accomodate API users that get the model object from the TheoryEngine,
 766    * where we want to ensure that this model is always valid.
 767    * TODO (#2648): revisit this.
 768    */
 769   void setEagerModelBuilding() { d_eager_model_building = true; }
 770
 771   /** get synth solutions
 772    *
 773    * This function adds entries to sol_map that map functions-to-synthesize with
 774    * their solutions, for all active conjectures. This should be called
 775    * immediately after the solver answers unsat for sygus input.
 776    *
 777    * For details on what is added to sol_map, see
 778    * CegConjecture::getSynthSolutions.
 779    */
 780   void getSynthSolutions(std::map<Node, Node>& sol_map);
 781
 782   /**
 783    * Get the model builder
 784    */
 785   theory::TheoryEngineModelBuilder* getModelBuilder() { return d_curr_model_builder; }
 786
 787   /**
 788    * Get the theory associated to a given Node.
 789    *
 790    * @returns the theory, or NULL if the TNode is
 791    * of built-in type.
 792    */
 793   inline theory::Theory* theoryOf(TNode node) const {
 794     return d_theoryTable[theory::Theory::theoryOf(node)];
 795   }
 796
 797   /**
 798    * Get the theory associated to a the given theory id.
 799    *
 800    * @returns the theory
 801    */
 802   inline theory::Theory* theoryOf(theory::TheoryId theoryId) const {
 803     return d_theoryTable[theoryId];
 804   }
 805
 806   inline bool isTheoryEnabled(theory::TheoryId theoryId) const {
 807     return d_logicInfo.isTheoryEnabled(theoryId);
 808   }
 809   /** get the logic info used by this theory engine */
 810   const LogicInfo& getLogicInfo() const;
 811   /**
 812    * Returns the equality status of the two terms, from the theory
 813    * that owns the domain type.  The types of a and b must be the same.
 814    */
 815   theory::EqualityStatus getEqualityStatus(TNode a, TNode b);
 816
 817   /**
 818    * Returns the value that a theory that owns the type of var currently
 819    * has (or null if none);
 820    */
 821   Node getModelValue(TNode var);
 822
 823   /**
 824    * Takes a literal and returns an equivalent literal that is guaranteed to be a SAT literal
 825    */
 826   Node ensureLiteral(TNode n);
 827
 828   /**
 829    * Print all instantiations made by the quantifiers module.
 830    */
 831   void printInstantiations( std::ostream& out );
 832
 833   /**
 834    * Print solution for synthesis conjectures found by ce_guided_instantiation module
 835    */
 836   void printSynthSolution( std::ostream& out );
 837
 838   /**
 839    * Get list of quantified formulas that were instantiated
 840    */
 841   void getInstantiatedQuantifiedFormulas( std::vector< Node >& qs );
 842
 843   /**
 844    * Get instantiation methods
 845    *   first inputs forall x.q[x] and returns ( q[a], ..., q[z] )
 846    *   second inputs forall x.q[x] and returns ( a, ..., z )
 847    *   third and fourth return mappings e.g. forall x.q1[x] -> ( q1[a]...q1[z] ) , ... , forall x.qn[x] -> ( qn[a]...qn[z] )
 848    */
 849   void getInstantiations( Node q, std::vector< Node >& insts );
 850   void getInstantiationTermVectors( Node q, std::vector< std::vector< Node > >& tvecs );
 851   void getInstantiations( std::map< Node, std::vector< Node > >& insts );
 852   void getInstantiationTermVectors( std::map< Node, std::vector< std::vector< Node > > >& insts );
 853
 854   /**
 855    * Get instantiated conjunction, returns q[t1] ^ ... ^ q[tn] where t1...tn are current set of instantiations for q.
 856    *   Can be used for quantifier elimination when satisfiable and q[t1] ^ ... ^ q[tn] |= q
 857    */
 858   Node getInstantiatedConjunction( Node q );
 859
 860   /**
 861    * Forwards an entailment check according to the given theoryOfMode.
 862    * See theory.h for documentation on entailmentCheck().
 863    */
 864   std::pair<bool, Node> entailmentCheck(theory::TheoryOfMode mode, TNode lit, const theory::EntailmentCheckParameters* params = NULL, theory::EntailmentCheckSideEffects* out = NULL);
 865
 866 private:
 867
 868   /** Default visitor for pre-registration */
 869   PreRegisterVisitor d_preRegistrationVisitor;
 870
 871   /** Visitor for collecting shared terms */
 872   SharedTermsVisitor d_sharedTermsVisitor;
 873
 874   /** Dump the assertions to the dump */
 875   void dumpAssertions(const char* tag);
 876
 877   /** For preprocessing pass lifting bit-vectors of size 1 to booleans */
 878 public:
 879   void staticInitializeBVOptions(const std::vector<Node>& assertions);
 880
 881   Node ppSimpITE(TNode assertion);
 882   /** Returns false if an assertion simplified to false. */
 883   bool donePPSimpITE(std::vector<Node>& assertions);
 884
 885   SharedTermsDatabase* getSharedTermsDatabase() { return &d_sharedTerms; }
 886
 887   theory::eq::EqualityEngine* getMasterEqualityEngine() { return d_masterEqualityEngine; }
 888
 889   RemoveTermFormulas* getTermFormulaRemover() { return &d_tform_remover; }
 890
 891   SortInference* getSortInference() { return &d_sortInfer; }
 892
 893   /** Prints the assertions to the debug stream */
 894   void printAssertions(const char* tag);
 895
 896   /** Theory alternative is in use. */
 897   bool useTheoryAlternative(const std::string& name);
 898
 899   /** Enables using a theory alternative by name. */
 900   void enableTheoryAlternative(const std::string& name);
 901
 902 private:
 903   std::set< std::string > d_theoryAlternatives;
 904
 905   std::map< std::string, std::vector< theory::Theory* > > d_attr_handle;
 906
 907  public:
 908   /** Set user attribute.
 909    *
 910    * This function is called when an attribute is set by a user.  In SMT-LIBv2
 911    * this is done via the syntax (! n :attr)
 912    */
 913   void setUserAttribute(const std::string& attr,
 914                         Node n,
 915                         const std::vector<Node>& node_values,
 916                         const std::string& str_value);
 917
 918   /** Handle user attribute.
 919    *
 920    * Associates theory t with the attribute attr.  Theory t will be
 921    * notified whenever an attribute of name attr is set.
 922    */
 923   void handleUserAttribute(const char* attr, theory::Theory* t);
 924
 925   /**
 926    * Check that the theory assertions are satisfied in the model.
 927    * This function is called from the smt engine's checkModel routine.
 928    */
 929   void checkTheoryAssertionsWithModel(bool hardFailure);
 930
 931  private:
 932   IntStat d_arithSubstitutionsAdded;
 933
 934 };/* class TheoryEngine */
 935
 936 }/* CVC4 namespace */
 937
 938 #endif /* CVC4__THEORY_ENGINE_H */