src/theory/bv/bv_subtheory_core.cpp

   1 /*********************                                                        */
   2 /*! \file bv_subtheory_core.cpp
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Liana Hadarean, Andrew Reynolds, Tim King
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2016 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 Algebraic solver.
  13  **
  14  ** Algebraic solver.
  15  **/
  16
  17 #include "theory/bv/bv_subtheory_core.h"
  18
  19 #include "options/bv_options.h"
  20 #include "options/smt_options.h"
  21 #include "smt/smt_statistics_registry.h"
  22 #include "theory/bv/slicer.h"
  23 #include "theory/bv/theory_bv.h"
  24 #include "theory/bv/theory_bv_utils.h"
  25 #include "theory/theory_model.h"
  26
  27 using namespace std;
  28 using namespace CVC4;
  29 using namespace CVC4::context;
  30 using namespace CVC4::theory;
  31 using namespace CVC4::theory::bv;
  32 using namespace CVC4::theory::bv::utils;
  33
  34 CoreSolver::CoreSolver(context::Context* c, TheoryBV* bv)
  35   : SubtheorySolver(c, bv),
  36     d_notify(*this),
  37     d_equalityEngine(d_notify, c, "theory::bv::TheoryBV", true),
  38     d_slicer(new Slicer()),
  39     d_isComplete(c, true),
  40     d_lemmaThreshold(16),
  41     d_useSlicer(false),
  42     d_preregisterCalled(false),
  43     d_checkCalled(false),
  44     d_reasons(c)
  45 {
  46   // The kinds we are treating as function application in congruence
  47   d_equalityEngine.addFunctionKind(kind::BITVECTOR_CONCAT, true);
  48   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_AND);
  49   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_OR);
  50   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XOR);
  51   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOT);
  52   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NAND);
  53   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOR);
  54   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XNOR);
  55   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_COMP);
  56   d_equalityEngine.addFunctionKind(kind::BITVECTOR_MULT, true);
  57   d_equalityEngine.addFunctionKind(kind::BITVECTOR_PLUS, true);
  58   d_equalityEngine.addFunctionKind(kind::BITVECTOR_EXTRACT, true);
  59   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SUB);
  60   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NEG);
  61   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UDIV);
  62   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UREM);
  63   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SDIV);
  64   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SREM);
  65   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SMOD);
  66   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SHL);
  67   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_LSHR);
  68   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ASHR);
  69   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULT);
  70   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULE);
  71   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGT);
  72   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGE);
  73   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLT);
  74   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLE);
  75   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGT);
  76   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGE);
  77   d_equalityEngine.addFunctionKind(kind::BITVECTOR_TO_NAT);
  78   d_equalityEngine.addFunctionKind(kind::INT_TO_BITVECTOR);
  79 }
  80
  81 CoreSolver::~CoreSolver() {
  82   delete d_slicer;
  83 }
  84 void CoreSolver::setMasterEqualityEngine(eq::EqualityEngine* eq) {
  85   d_equalityEngine.setMasterEqualityEngine(eq);
  86 }
  87
  88 void CoreSolver::enableSlicer() {
  89   AlwaysAssert (!d_preregisterCalled);
  90   d_useSlicer = true;
  91   d_statistics.d_slicerEnabled.setData(true);
  92 }
  93
  94 void CoreSolver::preRegister(TNode node) {
  95   d_preregisterCalled = true;
  96   if (node.getKind() == kind::EQUAL) {
  97       d_equalityEngine.addTriggerEquality(node);
  98       if (d_useSlicer) {
  99         d_slicer->processEquality(node);
 100         AlwaysAssert(!d_checkCalled);
 101       }
 102   } else {
 103     d_equalityEngine.addTerm(node);
 104   }
 105 }
 106
 107
 108 void CoreSolver::explain(TNode literal, std::vector<TNode>& assumptions) {
 109   bool polarity = literal.getKind() != kind::NOT;
 110   TNode atom = polarity ? literal : literal[0];
 111   if (atom.getKind() == kind::EQUAL) {
 112     d_equalityEngine.explainEquality(atom[0], atom[1], polarity, assumptions);
 113   } else {
 114     d_equalityEngine.explainPredicate(atom, polarity, assumptions);
 115   }
 116 }
 117
 118 Node CoreSolver::getBaseDecomposition(TNode a) {
 119   std::vector<Node> a_decomp;
 120   d_slicer->getBaseDecomposition(a, a_decomp);
 121   Node new_a = utils::mkConcat(a_decomp);
 122   Debug("bv-slicer") << "CoreSolver::getBaseDecomposition " << a <<" => " << new_a << "\n";
 123   return new_a;
 124 }
 125
 126 bool CoreSolver::decomposeFact(TNode fact) {
 127   Debug("bv-slicer") << "CoreSolver::decomposeFact fact=" << fact << endl;
 128   // FIXME: are this the right things to assert?
 129   // assert decompositions since the equality engine does not know the semantics of
 130   // concat:
 131   //   a == a_1 concat ... concat a_k
 132   //   b == b_1 concat ... concat b_k
 133   TNode eq = fact.getKind() == kind::NOT? fact[0] : fact;
 134
 135   TNode a = eq[0];
 136   TNode b = eq[1];
 137   Node new_a = getBaseDecomposition(a);
 138   Node new_b = getBaseDecomposition(b);
 139
 140   Assert (utils::getSize(new_a) == utils::getSize(new_b) &&
 141           utils::getSize(new_a) == utils::getSize(a));
 142
 143   NodeManager* nm = NodeManager::currentNM();
 144   Node a_eq_new_a = nm->mkNode(kind::EQUAL, a, new_a);
 145   Node b_eq_new_b = nm->mkNode(kind::EQUAL, b, new_b);
 146
 147   bool ok = true;
 148   ok = assertFactToEqualityEngine(a_eq_new_a, utils::mkTrue());
 149   if (!ok) return false;
 150   ok = assertFactToEqualityEngine(b_eq_new_b, utils::mkTrue());
 151   if (!ok) return false;
 152   ok = assertFactToEqualityEngine(fact, fact);
 153   if (!ok) return false;
 154
 155   if (fact.getKind() == kind::EQUAL) {
 156     // assert the individual equalities as well
 157     //    a_i == b_i
 158     if (new_a.getKind() == kind::BITVECTOR_CONCAT &&
 159         new_b.getKind() == kind::BITVECTOR_CONCAT) {
 160
 161       Assert (new_a.getNumChildren() == new_b.getNumChildren());
 162       for (unsigned i = 0; i < new_a.getNumChildren(); ++i) {
 163         Node eq_i = nm->mkNode(kind::EQUAL, new_a[i], new_b[i]);
 164         ok = assertFactToEqualityEngine(eq_i, fact);
 165         if (!ok) return false;
 166       }
 167     }
 168   }
 169   return true;
 170 }
 171
 172 bool CoreSolver::check(Theory::Effort e) {
 173   Trace("bitvector::core") << "CoreSolver::check \n";
 174
 175   d_bv->spendResource(options::theoryCheckStep());
 176
 177   d_checkCalled = true;
 178   Assert (!d_bv->inConflict());
 179   ++(d_statistics.d_numCallstoCheck);
 180   bool ok = true;
 181   std::vector<Node> core_eqs;
 182   TNodeBoolMap seen;
 183   // slicer does not deal with cardinality constraints yet
 184   if (d_useSlicer) {
 185     d_isComplete = false;
 186   }
 187   while (! done()) {
 188     TNode fact = get();
 189     if (d_isComplete && !isCompleteForTerm(fact, seen)) {
 190       d_isComplete = false;
 191     }
 192
 193     // only reason about equalities
 194     if (fact.getKind() == kind::EQUAL || (fact.getKind() == kind::NOT && fact[0].getKind() == kind::EQUAL)) {
 195       if (d_useSlicer) {
 196         ok = decomposeFact(fact);
 197       } else {
 198         ok = assertFactToEqualityEngine(fact, fact);
 199       }
 200     } else {
 201       ok = assertFactToEqualityEngine(fact, fact);
 202     }
 203     if (!ok)
 204       return false;
 205   }
 206
 207   if (Theory::fullEffort(e) && isComplete()) {
 208     buildModel();
 209   }
 210
 211   return true;
 212 }
 213
 214 void CoreSolver::buildModel() {
 215   Debug("bv-core") << "CoreSolver::buildModel() \n";
 216   d_modelValues.clear();
 217   TNodeSet constants;
 218   TNodeSet constants_in_eq_engine;
 219   // collect constants in equality engine
 220   eq::EqClassesIterator eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 221   while (!eqcs_i.isFinished()) {
 222     TNode repr = *eqcs_i;
 223     if  (repr.getKind() == kind::CONST_BITVECTOR) {
 224       // must check if it's just the constant
 225       eq::EqClassIterator it(repr, &d_equalityEngine);
 226       if (!(++it).isFinished() || true) {
 227         constants.insert(repr);
 228         constants_in_eq_engine.insert(repr);
 229       }
 230     }
 231     ++eqcs_i;
 232   }
 233
 234   // build repr to value map
 235
 236   eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 237   while (!eqcs_i.isFinished()) {
 238     TNode repr = *eqcs_i;
 239     ++eqcs_i;
 240
 241     if (!repr.isVar() &&
 242         repr.getKind() != kind::CONST_BITVECTOR &&
 243         !d_bv->isSharedTerm(repr)) {
 244       continue;
 245     }
 246
 247     TypeNode type = repr.getType();
 248     if (type.isBitVector() && repr.getKind()!= kind::CONST_BITVECTOR) {
 249       Debug("bv-core-model") << "   processing " << repr <<"\n";
 250       // we need to assign a value for it
 251       TypeEnumerator te(type);
 252       Node val;
 253       do {
 254         val = *te;
 255         ++te;
 256         // Debug("bv-core-model") << "  trying value " << val << "\n";
 257         // Debug("bv-core-model") << "  is in set? " << constants.count(val) << "\n";
 258         // Debug("bv-core-model") << "  enumerator done? " << te.isFinished() << "\n";
 259       } while (constants.count(val) != 0 && !(te.isFinished()));
 260
 261       if (te.isFinished() && constants.count(val) != 0) {
 262         // if we cannot enumerate anymore values we just return the lemma stating that
 263         // at least two of the representatives are equal.
 264         std::vector<TNode> representatives;
 265         representatives.push_back(repr);
 266
 267         for (TNodeSet::const_iterator it = constants_in_eq_engine.begin();
 268              it != constants_in_eq_engine.end(); ++it) {
 269           TNode constant = *it;
 270           if (utils::getSize(constant) == utils::getSize(repr)) {
 271             representatives.push_back(constant);
 272           }
 273         }
 274         for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 275           representatives.push_back(it->first);
 276         }
 277         std::vector<Node> equalities;
 278         for (unsigned i = 0; i < representatives.size(); ++i) {
 279           for (unsigned j = i + 1; j < representatives.size(); ++j) {
 280             TNode a = representatives[i];
 281             TNode b = representatives[j];
 282             if (a.getKind() == kind::CONST_BITVECTOR &&
 283                 b.getKind() == kind::CONST_BITVECTOR) {
 284               Assert (a != b);
 285               continue;
 286             }
 287             if (utils::getSize(a) == utils::getSize(b)) {
 288               equalities.push_back(utils::mkNode(kind::EQUAL, a, b));
 289             }
 290           }
 291         }
 292         // better off letting the SAT solver split on values
 293         if (equalities.size() > d_lemmaThreshold) {
 294           d_isComplete = false;
 295           return;
 296         }
 297
 298         Node lemma = utils::mkOr(equalities);
 299         d_bv->lemma(lemma);
 300         Debug("bv-core") << "  lemma: " << lemma << "\n";
 301         return;
 302       }
 303
 304       Debug("bv-core-model") << "   " << repr << " => " << val <<"\n" ;
 305       constants.insert(val);
 306       d_modelValues[repr] = val;
 307     }
 308   }
 309 }
 310
 311 bool CoreSolver::assertFactToEqualityEngine(TNode fact, TNode reason) {
 312   // Notify the equality engine
 313   if (!d_bv->inConflict() && (!d_bv->wasPropagatedBySubtheory(fact) || d_bv->getPropagatingSubtheory(fact) != SUB_CORE)) {
 314     Debug("bv-slicer-eq") << "CoreSolver::assertFactToEqualityEngine fact=" << fact << endl;
 315     // Debug("bv-slicer-eq") << "                     reason=" << reason << endl;
 316     bool negated = fact.getKind() == kind::NOT;
 317     TNode predicate = negated ? fact[0] : fact;
 318     if (predicate.getKind() == kind::EQUAL) {
 319       if (negated) {
 320         // dis-equality
 321         d_equalityEngine.assertEquality(predicate, false, reason);
 322       } else {
 323         // equality
 324         d_equalityEngine.assertEquality(predicate, true, reason);
 325       }
 326     } else {
 327       // Adding predicate if the congruence over it is turned on
 328       if (d_equalityEngine.isFunctionKind(predicate.getKind())) {
 329         d_equalityEngine.assertPredicate(predicate, !negated, reason);
 330       }
 331     }
 332   }
 333
 334   // checking for a conflict
 335   if (d_bv->inConflict()) {
 336     return false;
 337   }
 338   return true;
 339 }
 340
 341 bool CoreSolver::NotifyClass::eqNotifyTriggerEquality(TNode equality, bool value) {
 342   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerEquality(" << equality << ", " << (value ? "true" : "false" )<< ")" << std::endl;
 343   if (value) {
 344     return d_solver.storePropagation(equality);
 345   } else {
 346     return d_solver.storePropagation(equality.notNode());
 347   }
 348 }
 349
 350 bool CoreSolver::NotifyClass::eqNotifyTriggerPredicate(TNode predicate, bool value) {
 351   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerPredicate(" << predicate << ", " << (value ? "true" : "false" ) << ")" << std::endl;
 352   if (value) {
 353     return d_solver.storePropagation(predicate);
 354   } else {
 355     return d_solver.storePropagation(predicate.notNode());
 356   }
 357 }
 358
 359 bool CoreSolver::NotifyClass::eqNotifyTriggerTermEquality(TheoryId tag, TNode t1, TNode t2, bool value) {
 360   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerTermMerge(" << t1 << ", " << t2 << ")" << std::endl;
 361   if (value) {
 362     return d_solver.storePropagation(t1.eqNode(t2));
 363   } else {
 364     return d_solver.storePropagation(t1.eqNode(t2).notNode());
 365   }
 366 }
 367
 368 void CoreSolver::NotifyClass::eqNotifyConstantTermMerge(TNode t1, TNode t2) {
 369   d_solver.conflict(t1, t2);
 370 }
 371
 372 void CoreSolver::NotifyClass::eqNotifyNewClass(TNode t) {
 373   d_solver.eqNotifyNewClass( t );
 374 }
 375
 376 bool CoreSolver::storePropagation(TNode literal) {
 377   return d_bv->storePropagation(literal, SUB_CORE);
 378 }
 379
 380 void CoreSolver::conflict(TNode a, TNode b) {
 381   std::vector<TNode> assumptions;
 382   d_equalityEngine.explainEquality(a, b, true, assumptions);
 383   Node conflict = flattenAnd(assumptions);
 384   d_bv->setConflict(conflict);
 385 }
 386
 387 void CoreSolver::eqNotifyNewClass(TNode t) {
 388   Assert( d_bv->getExtTheory()!=NULL );
 389   d_bv->getExtTheory()->registerTerm( t );
 390 }
 391
 392 bool CoreSolver::isCompleteForTerm(TNode term, TNodeBoolMap& seen) {
 393   if (d_useSlicer)
 394     return utils::isCoreTerm(term, seen);
 395
 396   return utils::isEqualityTerm(term, seen);
 397 }
 398
 399 void CoreSolver::collectModelInfo(TheoryModel* m, bool fullModel) {
 400   if (d_useSlicer) {
 401     Unreachable();
 402   }
 403   if (Debug.isOn("bitvector-model")) {
 404     context::CDQueue<Node>::const_iterator it = d_assertionQueue.begin();
 405     for (; it!= d_assertionQueue.end(); ++it) {
 406       Debug("bitvector-model") << "CoreSolver::collectModelInfo (assert "
 407                                << *it << ")\n";
 408     }
 409   }
 410   set<Node> termSet;
 411   d_bv->computeRelevantTerms(termSet);
 412   m->assertEqualityEngine(&d_equalityEngine, &termSet);
 413   if (isComplete()) {
 414     Debug("bitvector-model") << "CoreSolver::collectModelInfo complete.";
 415     for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 416       Node a = it->first;
 417       Node b = it->second;
 418       Debug("bitvector-model") << "CoreSolver::collectModelInfo modelValues "
 419                                << a << " => " << b <<")\n";
 420       m->assertEquality(a, b, true);
 421     }
 422   }
 423 }
 424
 425 Node CoreSolver::getModelValue(TNode var) {
 426   // we don't need to evaluate bv expressions and only look at variable values
 427   // because this only gets called when the core theory is complete (i.e. no other bv
 428   // function symbols are currently asserted)
 429   Assert (d_slicer->isCoreTerm(var));
 430
 431   Debug("bitvector-model") << "CoreSolver::getModelValue (" << var <<")";
 432   Assert (isComplete());
 433   TNode repr = d_equalityEngine.getRepresentative(var);
 434   Node result = Node();
 435   if (repr.getKind() == kind::CONST_BITVECTOR) {
 436     result = repr;
 437   } else if (d_modelValues.find(repr) == d_modelValues.end()) {
 438     // it may be a shared term that never gets asserted
 439     // result is just Null
 440     Assert(d_bv->isSharedTerm(var));
 441   } else {
 442     result = d_modelValues[repr];
 443   }
 444   Debug("bitvector-model") << " => " << result <<"\n";
 445   return result;
 446 }
 447
 448 CoreSolver::Statistics::Statistics()
 449   : d_numCallstoCheck("theory::bv::CoreSolver::NumCallsToCheck", 0)
 450   , d_slicerEnabled("theory::bv::CoreSolver::SlicerEnabled", false)
 451 {
 452   smtStatisticsRegistry()->registerStat(&d_numCallstoCheck);
 453   smtStatisticsRegistry()->registerStat(&d_slicerEnabled);
 454 }
 455 CoreSolver::Statistics::~Statistics() {
 456   smtStatisticsRegistry()->unregisterStat(&d_numCallstoCheck);
 457   smtStatisticsRegistry()->unregisterStat(&d_slicerEnabled);
 458 }