src/theory/theory.cpp

   1 /*********************                                                        */
   2 /*! \file theory.cpp
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Tim King, Mathias Preiner, Dejan Jovanovic
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2020 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 Base for theory interface.
  13  **
  14  ** Base for theory interface.
  15  **/
  16
  17 #include "theory/theory.h"
  18
  19 #include <iostream>
  20 #include <sstream>
  21 #include <string>
  22 #include <vector>
  23
  24 #include "base/check.h"
  25 #include "expr/node_algorithm.h"
  26 #include "options/theory_options.h"
  27 #include "smt/smt_statistics_registry.h"
  28 #include "theory/ext_theory.h"
  29 #include "theory/quantifiers_engine.h"
  30 #include "theory/substitutions.h"
  31 #include "theory/theory_rewriter.h"
  32
  33 using namespace std;
  34
  35 namespace CVC4 {
  36 namespace theory {
  37
  38 /** Default value for the uninterpreted sorts is the UF theory */
  39 TheoryId Theory::s_uninterpretedSortOwner = THEORY_UF;
  40
  41 std::ostream& operator<<(std::ostream& os, Theory::Effort level){
  42   switch(level){
  43   case Theory::EFFORT_STANDARD:
  44     os << "EFFORT_STANDARD"; break;
  45   case Theory::EFFORT_FULL:
  46     os << "EFFORT_FULL"; break;
  47   case Theory::EFFORT_LAST_CALL:
  48     os << "EFFORT_LAST_CALL"; break;
  49   default:
  50       Unreachable();
  51   }
  52   return os;
  53 }/* ostream& operator<<(ostream&, Theory::Effort) */
  54
  55 Theory::Theory(TheoryId id,
  56                context::Context* satContext,
  57                context::UserContext* userContext,
  58                OutputChannel& out,
  59                Valuation valuation,
  60                const LogicInfo& logicInfo,
  61                ProofNodeManager* pnm,
  62                std::string name)
  63     : d_id(id),
  64       d_satContext(satContext),
  65       d_userContext(userContext),
  66       d_logicInfo(logicInfo),
  67       d_pnm(pnm),
  68       d_facts(satContext),
  69       d_factsHead(satContext, 0),
  70       d_sharedTermsIndex(satContext, 0),
  71       d_careGraph(NULL),
  72       d_quantEngine(NULL),
  73       d_decManager(nullptr),
  74       d_instanceName(name),
  75       d_checkTime(getStatsPrefix(id) + name + "::checkTime"),
  76       d_computeCareGraphTime(getStatsPrefix(id) + name
  77                              + "::computeCareGraphTime"),
  78       d_sharedTerms(satContext),
  79       d_out(&out),
  80       d_valuation(valuation),
  81       d_equalityEngine(nullptr),
  82       d_allocEqualityEngine(nullptr),
  83       d_theoryState(nullptr),
  84       d_proofsEnabled(false)
  85 {
  86   smtStatisticsRegistry()->registerStat(&d_checkTime);
  87   smtStatisticsRegistry()->registerStat(&d_computeCareGraphTime);
  88 }
  89
  90 Theory::~Theory() {
  91   smtStatisticsRegistry()->unregisterStat(&d_checkTime);
  92   smtStatisticsRegistry()->unregisterStat(&d_computeCareGraphTime);
  93 }
  94
  95 bool Theory::needsEqualityEngine(EeSetupInfo& esi)
  96 {
  97   // by default, this theory does not use an (official) equality engine
  98   return false;
  99 }
 100
 101 void Theory::setEqualityEngine(eq::EqualityEngine* ee)
 102 {
 103   // set the equality engine pointer
 104   d_equalityEngine = ee;
 105   if (d_theoryState != nullptr)
 106   {
 107     d_theoryState->setEqualityEngine(ee);
 108   }
 109 }
 110
 111 void Theory::setQuantifiersEngine(QuantifiersEngine* qe)
 112 {
 113   Assert(d_quantEngine == nullptr);
 114   // quantifiers engine may be null if not in quantified logic
 115   d_quantEngine = qe;
 116 }
 117
 118 void Theory::setDecisionManager(DecisionManager* dm)
 119 {
 120   Assert(d_decManager == nullptr);
 121   Assert(dm != nullptr);
 122   d_decManager = dm;
 123 }
 124
 125 void Theory::finishInitStandalone()
 126 {
 127   EeSetupInfo esi;
 128   if (needsEqualityEngine(esi))
 129   {
 130     // always associated with the same SAT context as the theory (d_satContext)
 131     d_allocEqualityEngine.reset(new eq::EqualityEngine(
 132         *esi.d_notify, d_satContext, esi.d_name, esi.d_constantsAreTriggers));
 133     // use it as the official equality engine
 134     setEqualityEngine(d_allocEqualityEngine.get());
 135   }
 136   finishInit();
 137 }
 138
 139 TheoryId Theory::theoryOf(options::TheoryOfMode mode, TNode node)
 140 {
 141   TheoryId tid = THEORY_BUILTIN;
 142   switch(mode) {
 143     case options::TheoryOfMode::THEORY_OF_TYPE_BASED:
 144       // Constants, variables, 0-ary constructors
 145       if (node.isVar())
 146       {
 147         if (node.getKind() == kind::BOOLEAN_TERM_VARIABLE)
 148         {
 149           tid = THEORY_UF;
 150         }
 151         else
 152         {
 153           tid = Theory::theoryOf(node.getType());
 154         }
 155       }
 156       else if (node.isConst())
 157       {
 158         tid = Theory::theoryOf(node.getType());
 159       }
 160       else if (node.getKind() == kind::EQUAL)
 161       {
 162         // Equality is owned by the theory that owns the domain
 163         tid = Theory::theoryOf(node[0].getType());
 164       }
 165       else
 166       {
 167         // Regular nodes are owned by the kind
 168         tid = kindToTheoryId(node.getKind());
 169       }
 170       break;
 171     case options::TheoryOfMode::THEORY_OF_TERM_BASED:
 172       // Variables
 173       if (node.isVar())
 174       {
 175         if (Theory::theoryOf(node.getType()) != theory::THEORY_BOOL)
 176         {
 177           // We treat the variables as uninterpreted
 178           tid = s_uninterpretedSortOwner;
 179         }
 180         else
 181         {
 182           if (node.getKind() == kind::BOOLEAN_TERM_VARIABLE)
 183           {
 184             // Boolean vars go to UF
 185             tid = THEORY_UF;
 186           }
 187           else
 188           {
 189             // Except for the Boolean ones
 190             tid = THEORY_BOOL;
 191           }
 192         }
 193       }
 194       else if (node.isConst())
 195       {
 196         // Constants go to the theory of the type
 197         tid = Theory::theoryOf(node.getType());
 198       }
 199       else if (node.getKind() == kind::EQUAL)
 200       {  // Equality
 201         // If one of them is an ITE, it's irelevant, since they will get
 202         // replaced out anyhow
 203         if (node[0].getKind() == kind::ITE)
 204         {
 205           tid = Theory::theoryOf(node[0].getType());
 206         }
 207         else if (node[1].getKind() == kind::ITE)
 208         {
 209           tid = Theory::theoryOf(node[1].getType());
 210         }
 211         else
 212         {
 213           TNode l = node[0];
 214           TNode r = node[1];
 215           TypeNode ltype = l.getType();
 216           TypeNode rtype = r.getType();
 217           if (ltype != rtype)
 218           {
 219             tid = Theory::theoryOf(l.getType());
 220           }
 221           else
 222           {
 223             // If both sides belong to the same theory the choice is easy
 224             TheoryId T1 = Theory::theoryOf(l);
 225             TheoryId T2 = Theory::theoryOf(r);
 226             if (T1 == T2)
 227             {
 228               tid = T1;
 229             }
 230             else
 231             {
 232               TheoryId T3 = Theory::theoryOf(ltype);
 233               // This is a case of
 234               // * x*y = f(z) -> UF
 235               // * x = c      -> UF
 236               // * f(x) = read(a, y) -> either UF or ARRAY
 237               // at least one of the theories has to be parametric, i.e. theory
 238               // of the type is different from the theory of the term
 239               if (T1 == T3)
 240               {
 241                 tid = T2;
 242               }
 243               else if (T2 == T3)
 244               {
 245                 tid = T1;
 246               }
 247               else
 248               {
 249                 // If both are parametric, we take the smaller one (arbitrary)
 250                 tid = T1 < T2 ? T1 : T2;
 251               }
 252             }
 253           }
 254         }
 255       }
 256       else
 257       {
 258         // Regular nodes are owned by the kind
 259         tid = kindToTheoryId(node.getKind());
 260       }
 261     break;
 262   default:
 263     Unreachable();
 264   }
 265   Trace("theory::internal") << "theoryOf(" << mode << ", " << node << ") -> " << tid << std::endl;
 266   return tid;
 267 }
 268
 269 void Theory::notifySharedTerm(TNode n)
 270 {
 271   // TODO (project #39): this will move to addSharedTerm, as every theory with
 272   // an equality does this in their notifySharedTerm method.
 273   // if we have an equality engine, add the trigger term
 274   if (d_equalityEngine != nullptr)
 275   {
 276     d_equalityEngine->addTriggerTerm(n, d_id);
 277   }
 278 }
 279
 280 void Theory::computeCareGraph() {
 281   Debug("sharing") << "Theory::computeCareGraph<" << getId() << ">()" << endl;
 282   for (unsigned i = 0; i < d_sharedTerms.size(); ++ i) {
 283     TNode a = d_sharedTerms[i];
 284     TypeNode aType = a.getType();
 285     for (unsigned j = i + 1; j < d_sharedTerms.size(); ++ j) {
 286       TNode b = d_sharedTerms[j];
 287       if (b.getType() != aType) {
 288         // We don't care about the terms of different types
 289         continue;
 290       }
 291       switch (d_valuation.getEqualityStatus(a, b)) {
 292       case EQUALITY_TRUE_AND_PROPAGATED:
 293       case EQUALITY_FALSE_AND_PROPAGATED:
 294         // If we know about it, we should have propagated it, so we can skip
 295         break;
 296       default:
 297         // Let's split on it
 298         addCarePair(a, b);
 299         break;
 300       }
 301     }
 302   }
 303 }
 304
 305 void Theory::printFacts(std::ostream& os) const {
 306   unsigned i, n = d_facts.size();
 307   for(i = 0; i < n; i++){
 308     const Assertion& a_i = d_facts[i];
 309     Node assertion  = a_i;
 310     os << d_id << '[' << i << ']' << " " << assertion << endl;
 311   }
 312 }
 313
 314 void Theory::debugPrintFacts() const{
 315   DebugChannel.getStream() << "Theory::debugPrintFacts()" << endl;
 316   printFacts(DebugChannel.getStream());
 317 }
 318
 319 bool Theory::isLegalElimination(TNode x, TNode val)
 320 {
 321   Assert(x.isVar());
 322   if (x.getKind() == kind::BOOLEAN_TERM_VARIABLE
 323       || val.getKind() == kind::BOOLEAN_TERM_VARIABLE)
 324   {
 325     return false;
 326   }
 327   if (expr::hasSubterm(val, x))
 328   {
 329     return false;
 330   }
 331   if (!val.getType().isSubtypeOf(x.getType()))
 332   {
 333     return false;
 334   }
 335   if (!options::produceModels())
 336   {
 337     // don't care about the model, we are fine
 338     return true;
 339   }
 340   // if there is a model object
 341   TheoryModel* tm = d_valuation.getModel();
 342   Assert(tm != nullptr);
 343   return tm->isLegalElimination(x, val);
 344 }
 345
 346 std::unordered_set<TNode, TNodeHashFunction> Theory::currentlySharedTerms() const{
 347   std::unordered_set<TNode, TNodeHashFunction> currentlyShared;
 348   for (shared_terms_iterator i = shared_terms_begin(),
 349            i_end = shared_terms_end(); i != i_end; ++i) {
 350     currentlyShared.insert (*i);
 351   }
 352   return currentlyShared;
 353 }
 354
 355 bool Theory::collectModelInfo(TheoryModel* m)
 356 {
 357   std::set<Node> termSet;
 358   // Compute terms appearing in assertions and shared terms
 359   computeRelevantTerms(termSet);
 360   // if we are using an equality engine, assert it to the model
 361   if (d_equalityEngine != nullptr)
 362   {
 363     if (!m->assertEqualityEngine(d_equalityEngine, &termSet))
 364     {
 365       return false;
 366     }
 367   }
 368   // now, collect theory-specific value assigments
 369   return collectModelValues(m, termSet);
 370 }
 371
 372 void Theory::collectTerms(TNode n,
 373                           set<Kind>& irrKinds,
 374                           set<Node>& termSet) const
 375 {
 376   if (termSet.find(n) != termSet.end()) {
 377     return;
 378   }
 379   Kind nk = n.getKind();
 380   if (irrKinds.find(nk) == irrKinds.end())
 381   {
 382     Trace("theory::collectTerms")
 383         << "Theory::collectTerms: adding " << n << endl;
 384     termSet.insert(n);
 385   }
 386   if (nk == kind::NOT || nk == kind::EQUAL || !isLeaf(n))
 387   {
 388     for(TNode::iterator child_it = n.begin(); child_it != n.end(); ++child_it) {
 389       collectTerms(*child_it, irrKinds, termSet);
 390     }
 391   }
 392 }
 393
 394 void Theory::computeRelevantTermsInternal(std::set<Node>& termSet,
 395                                           std::set<Kind>& irrKinds,
 396                                           bool includeShared) const
 397 {
 398   // Collect all terms appearing in assertions
 399   irrKinds.insert(kind::EQUAL);
 400   irrKinds.insert(kind::NOT);
 401   context::CDList<Assertion>::const_iterator assert_it = facts_begin(),
 402                                              assert_it_end = facts_end();
 403   for (; assert_it != assert_it_end; ++assert_it)
 404   {
 405     collectTerms(*assert_it, irrKinds, termSet);
 406   }
 407
 408   if (!includeShared)
 409   {
 410     return;
 411   }
 412   // Add terms that are shared terms
 413   std::set<Kind> kempty;
 414   context::CDList<TNode>::const_iterator shared_it = shared_terms_begin(),
 415                                          shared_it_end = shared_terms_end();
 416   for (; shared_it != shared_it_end; ++shared_it)
 417   {
 418     collectTerms(*shared_it, kempty, termSet);
 419   }
 420 }
 421
 422 void Theory::computeRelevantTerms(std::set<Node>& termSet, bool includeShared)
 423 {
 424   std::set<Kind> irrKinds;
 425   computeRelevantTermsInternal(termSet, irrKinds, includeShared);
 426 }
 427
 428 bool Theory::collectModelValues(TheoryModel* m, const std::set<Node>& termSet)
 429 {
 430   return true;
 431 }
 432
 433 Theory::PPAssertStatus Theory::ppAssert(TNode in,
 434                                         SubstitutionMap& outSubstitutions)
 435 {
 436   if (in.getKind() == kind::EQUAL)
 437   {
 438     // (and (= x t) phi) can be replaced by phi[x/t] if
 439     // 1) x is a variable
 440     // 2) x is not in the term t
 441     // 3) x : T and t : S, then S <: T
 442     if (in[0].isVar() && isLegalElimination(in[0], in[1])
 443         && in[0].getKind() != kind::BOOLEAN_TERM_VARIABLE)
 444     {
 445       outSubstitutions.addSubstitution(in[0], in[1]);
 446       return PP_ASSERT_STATUS_SOLVED;
 447     }
 448     if (in[1].isVar() && isLegalElimination(in[1], in[0])
 449         && in[1].getKind() != kind::BOOLEAN_TERM_VARIABLE)
 450     {
 451       outSubstitutions.addSubstitution(in[1], in[0]);
 452       return PP_ASSERT_STATUS_SOLVED;
 453     }
 454     if (in[0].isConst() && in[1].isConst())
 455     {
 456       if (in[0] != in[1])
 457       {
 458         return PP_ASSERT_STATUS_CONFLICT;
 459       }
 460     }
 461   }
 462
 463   return PP_ASSERT_STATUS_UNSOLVED;
 464 }
 465
 466 std::pair<bool, Node> Theory::entailmentCheck(TNode lit)
 467 {
 468   return make_pair(false, Node::null());
 469 }
 470
 471 void Theory::addCarePair(TNode t1, TNode t2) {
 472   if (d_careGraph) {
 473     d_careGraph->insert(CarePair(t1, t2, d_id));
 474   }
 475 }
 476
 477 void Theory::getCareGraph(CareGraph* careGraph) {
 478   Assert(careGraph != NULL);
 479
 480   Trace("sharing") << "Theory<" << getId() << ">::getCareGraph()" << std::endl;
 481   TimerStat::CodeTimer computeCareGraphTime(d_computeCareGraphTime);
 482   d_careGraph = careGraph;
 483   computeCareGraph();
 484   d_careGraph = NULL;
 485 }
 486
 487 EqualityStatus Theory::getEqualityStatus(TNode a, TNode b)
 488 {
 489   // if not using an equality engine, then by default we don't know the status
 490   if (d_equalityEngine == nullptr)
 491   {
 492     return EQUALITY_UNKNOWN;
 493   }
 494   Assert(d_equalityEngine->hasTerm(a) && d_equalityEngine->hasTerm(b));
 495
 496   // Check for equality (simplest)
 497   if (d_equalityEngine->areEqual(a, b))
 498   {
 499     // The terms are implied to be equal
 500     return EQUALITY_TRUE;
 501   }
 502
 503   // Check for disequality
 504   if (d_equalityEngine->areDisequal(a, b, false))
 505   {
 506     // The terms are implied to be dis-equal
 507     return EQUALITY_FALSE;
 508   }
 509
 510   // All other terms are unknown, which is conservative. A theory may override
 511   // this method if it knows more information.
 512   return EQUALITY_UNKNOWN;
 513 }
 514
 515 void Theory::check(Effort level)
 516 {
 517   // see if we are already done (as an optimization)
 518   if (done() && level < EFFORT_FULL)
 519   {
 520     return;
 521   }
 522   Assert(d_theoryState!=nullptr);
 523   // standard calls for resource, stats
 524   d_out->spendResource(ResourceManager::Resource::TheoryCheckStep);
 525   TimerStat::CodeTimer checkTimer(d_checkTime);
 526   // pre-check at level
 527   if (preCheck(level))
 528   {
 529     // check aborted for a theory-specific reason
 530     return;
 531   }
 532   // process the pending fact queue
 533   while (!done() && !d_theoryState->isInConflict())
 534   {
 535     // Get the next assertion from the fact queue
 536     Assertion assertion = get();
 537     TNode fact = assertion.d_assertion;
 538     bool polarity = fact.getKind() != kind::NOT;
 539     TNode atom = polarity ? fact : fact[0];
 540     // call the pre-notify method
 541     if (preNotifyFact(atom, polarity, fact, assertion.d_isPreregistered, false))
 542     {
 543       // handled in theory-specific way that doesn't involve equality engine
 544       continue;
 545     }
 546     // Theories that don't have an equality engine should always return true
 547     // for preNotifyFact
 548     Assert(d_equalityEngine != nullptr);
 549     // assert to the equality engine
 550     if (atom.getKind() == kind::EQUAL)
 551     {
 552       d_equalityEngine->assertEquality(atom, polarity, fact);
 553     }
 554     else
 555     {
 556       d_equalityEngine->assertPredicate(atom, polarity, fact);
 557     }
 558     // notify the theory of the new fact, which is not internal
 559     notifyFact(atom, polarity, fact, false);
 560   }
 561   // post-check at level
 562   postCheck(level);
 563 }
 564
 565 bool Theory::preCheck(Effort level) { return false; }
 566
 567 void Theory::postCheck(Effort level) {}
 568
 569 bool Theory::preNotifyFact(
 570     TNode atom, bool polarity, TNode fact, bool isPrereg, bool isInternal)
 571 {
 572   return false;
 573 }
 574
 575 void Theory::notifyFact(TNode atom, bool polarity, TNode fact, bool isInternal)
 576 {
 577 }
 578
 579 void Theory::preRegisterTerm(TNode node) {}
 580
 581 void Theory::addSharedTerm(TNode n)
 582 {
 583   Debug("sharing") << "Theory::addSharedTerm<" << getId() << ">(" << n << ")"
 584                    << std::endl;
 585   Debug("theory::assertions")
 586       << "Theory::addSharedTerm<" << getId() << ">(" << n << ")" << std::endl;
 587   d_sharedTerms.push_back(n);
 588   // now call theory-specific method notifySharedTerm
 589   notifySharedTerm(n);
 590 }
 591
 592 eq::EqualityEngine* Theory::getEqualityEngine()
 593 {
 594   // get the assigned equality engine, which is a pointer stored in this class
 595   return d_equalityEngine;
 596 }
 597
 598 }/* CVC4::theory namespace */
 599 }/* CVC4 namespace */