src/theory/bv/bv_subtheory_core.cpp

   1 /*********************                                                        */
   2 /*! \file bv_subtheory_core.cpp
   3  ** \verbatim
   4  ** Original author: Liana Hadarean
   5  ** Major contributors: Andrew Reynolds
   6  ** Minor contributors (to current version): Morgan Deters
   7  ** This file is part of the CVC4 project.
   8  ** Copyright (c) 2009-2014  New York University and The University of Iowa
   9  ** See the file COPYING in the top-level source directory for licensing
  10  ** information.\endverbatim
  11  **
  12  ** \brief Algebraic solver.
  13  **
  14  ** Algebraic solver.
  15  **/
  16
  17 #include "theory/bv/bv_subtheory_core.h"
  18
  19 #include "theory/bv/theory_bv.h"
  20 #include "theory/bv/theory_bv_utils.h"
  21 #include "theory/bv/slicer.h"
  22 #include "theory/theory_model.h"
  23 #include "theory/bv/options.h"
  24
  25 using namespace std;
  26 using namespace CVC4;
  27 using namespace CVC4::context;
  28 using namespace CVC4::theory;
  29 using namespace CVC4::theory::bv;
  30 using namespace CVC4::theory::bv::utils;
  31
  32 CoreSolver::CoreSolver(context::Context* c, TheoryBV* bv)
  33   : SubtheorySolver(c, bv),
  34     d_notify(*this),
  35     d_equalityEngine(d_notify, c, "theory::bv::TheoryBV", true),
  36     d_slicer(new Slicer()),
  37     d_isComplete(c, true),
  38     d_useSlicer(false),
  39     d_preregisterCalled(false),
  40     d_checkCalled(false),
  41     d_reasons(c)
  42 {
  43   // The kinds we are treating as function application in congruence
  44   d_equalityEngine.addFunctionKind(kind::BITVECTOR_CONCAT, true);
  45   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_AND);
  46   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_OR);
  47   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XOR);
  48   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOT);
  49   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NAND);
  50   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOR);
  51   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XNOR);
  52   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_COMP);
  53   d_equalityEngine.addFunctionKind(kind::BITVECTOR_MULT, true);
  54   d_equalityEngine.addFunctionKind(kind::BITVECTOR_PLUS, true);
  55   d_equalityEngine.addFunctionKind(kind::BITVECTOR_EXTRACT, true);
  56   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SUB);
  57   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NEG);
  58   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UDIV);
  59   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UREM);
  60   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SDIV);
  61   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SREM);
  62   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SMOD);
  63   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SHL);
  64   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_LSHR);
  65   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ASHR);
  66   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULT);
  67   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULE);
  68   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGT);
  69   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGE);
  70   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLT);
  71   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLE);
  72   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGT);
  73   //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGE);
  74 }
  75
  76 CoreSolver::~CoreSolver() {
  77   delete d_slicer;
  78 }
  79 void CoreSolver::setMasterEqualityEngine(eq::EqualityEngine* eq) {
  80   d_equalityEngine.setMasterEqualityEngine(eq);
  81 }
  82
  83 void CoreSolver::enableSlicer() {
  84   AlwaysAssert (!d_preregisterCalled);
  85   d_useSlicer = true;
  86   d_statistics.d_slicerEnabled.setData(true);
  87 }
  88
  89 void CoreSolver::preRegister(TNode node) {
  90   d_preregisterCalled = true;
  91   if (node.getKind() == kind::EQUAL) {
  92       d_equalityEngine.addTriggerEquality(node);
  93       if (d_useSlicer) {
  94         d_slicer->processEquality(node);
  95         AlwaysAssert(!d_checkCalled);
  96       }
  97   } else {
  98     d_equalityEngine.addTerm(node);
  99   }
 100 }
 101
 102
 103 void CoreSolver::explain(TNode literal, std::vector<TNode>& assumptions) {
 104   bool polarity = literal.getKind() != kind::NOT;
 105   TNode atom = polarity ? literal : literal[0];
 106   if (atom.getKind() == kind::EQUAL) {
 107     d_equalityEngine.explainEquality(atom[0], atom[1], polarity, assumptions);
 108   } else {
 109     d_equalityEngine.explainPredicate(atom, polarity, assumptions);
 110   }
 111 }
 112
 113 Node CoreSolver::getBaseDecomposition(TNode a) {
 114   std::vector<Node> a_decomp;
 115   d_slicer->getBaseDecomposition(a, a_decomp);
 116   Node new_a = utils::mkConcat(a_decomp);
 117   Debug("bv-slicer") << "CoreSolver::getBaseDecomposition " << a <<" => " << new_a << "\n";
 118   return new_a;
 119 }
 120
 121 bool CoreSolver::decomposeFact(TNode fact) {
 122   Debug("bv-slicer") << "CoreSolver::decomposeFact fact=" << fact << endl;
 123   // FIXME: are this the right things to assert?
 124   // assert decompositions since the equality engine does not know the semantics of
 125   // concat:
 126   //   a == a_1 concat ... concat a_k
 127   //   b == b_1 concat ... concat b_k
 128   TNode eq = fact.getKind() == kind::NOT? fact[0] : fact;
 129
 130   TNode a = eq[0];
 131   TNode b = eq[1];
 132   Node new_a = getBaseDecomposition(a);
 133   Node new_b = getBaseDecomposition(b);
 134
 135   Assert (utils::getSize(new_a) == utils::getSize(new_b) &&
 136           utils::getSize(new_a) == utils::getSize(a));
 137
 138   NodeManager* nm = NodeManager::currentNM();
 139   Node a_eq_new_a = nm->mkNode(kind::EQUAL, a, new_a);
 140   Node b_eq_new_b = nm->mkNode(kind::EQUAL, b, new_b);
 141
 142   bool ok = true;
 143   ok = assertFactToEqualityEngine(a_eq_new_a, utils::mkTrue());
 144   if (!ok) return false;
 145   ok = assertFactToEqualityEngine(b_eq_new_b, utils::mkTrue());
 146   if (!ok) return false;
 147   ok = assertFactToEqualityEngine(fact, fact);
 148   if (!ok) return false;
 149
 150   if (fact.getKind() == kind::EQUAL) {
 151     // assert the individual equalities as well
 152     //    a_i == b_i
 153     if (new_a.getKind() == kind::BITVECTOR_CONCAT &&
 154         new_b.getKind() == kind::BITVECTOR_CONCAT) {
 155
 156       Assert (new_a.getNumChildren() == new_b.getNumChildren());
 157       for (unsigned i = 0; i < new_a.getNumChildren(); ++i) {
 158         Node eq_i = nm->mkNode(kind::EQUAL, new_a[i], new_b[i]);
 159         ok = assertFactToEqualityEngine(eq_i, fact);
 160         if (!ok) return false;
 161       }
 162     }
 163   }
 164   return true;
 165 }
 166
 167 bool CoreSolver::check(Theory::Effort e) {
 168   Trace("bitvector::core") << "CoreSolver::check \n";
 169
 170   d_bv->spendResource();
 171
 172   d_checkCalled = true;
 173   Assert (!d_bv->inConflict());
 174   ++(d_statistics.d_numCallstoCheck);
 175   bool ok = true;
 176   std::vector<Node> core_eqs;
 177   TNodeBoolMap seen;
 178   // slicer does not deal with cardinality constraints yet
 179   if (d_useSlicer) {
 180     d_isComplete = false;
 181   }
 182   while (! done()) {
 183     TNode fact = get();
 184     if (d_isComplete && !isCompleteForTerm(fact, seen)) {
 185       d_isComplete = false;
 186     }
 187
 188     // only reason about equalities
 189     if (fact.getKind() == kind::EQUAL || (fact.getKind() == kind::NOT && fact[0].getKind() == kind::EQUAL)) {
 190       if (d_useSlicer) {
 191         ok = decomposeFact(fact);
 192       } else {
 193         ok = assertFactToEqualityEngine(fact, fact);
 194       }
 195     } else {
 196       ok = assertFactToEqualityEngine(fact, fact);
 197     }
 198     if (!ok)
 199       return false;
 200   }
 201
 202   if (Theory::fullEffort(e) && isComplete()) {
 203     buildModel();
 204   }
 205
 206   return true;
 207 }
 208
 209 void CoreSolver::buildModel() {
 210   Debug("bv-core") << "CoreSolver::buildModel() \n";
 211   d_modelValues.clear();
 212   TNodeSet constants;
 213   TNodeSet constants_in_eq_engine;
 214   // collect constants in equality engine
 215   eq::EqClassesIterator eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 216   while (!eqcs_i.isFinished()) {
 217     TNode repr = *eqcs_i;
 218     if  (repr.getKind() == kind::CONST_BITVECTOR) {
 219       // must check if it's just the constant
 220       eq::EqClassIterator it(repr, &d_equalityEngine);
 221       if (!(++it).isFinished() || true) {
 222         constants.insert(repr);
 223         constants_in_eq_engine.insert(repr);
 224       }
 225     }
 226     ++eqcs_i;
 227   }
 228
 229   // build repr to value map
 230
 231   eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 232   while (!eqcs_i.isFinished()) {
 233     TNode repr = *eqcs_i;
 234     ++eqcs_i;
 235
 236     if (repr.getKind() != kind::VARIABLE &&
 237         repr.getKind() != kind::SKOLEM &&
 238         repr.getKind() != kind::CONST_BITVECTOR &&
 239         !d_bv->isSharedTerm(repr)) {
 240       continue;
 241     }
 242
 243     TypeNode type = repr.getType();
 244     if (type.isBitVector() && repr.getKind()!= kind::CONST_BITVECTOR) {
 245       Debug("bv-core-model") << "   processing " << repr <<"\n";
 246       // we need to assign a value for it
 247       TypeEnumerator te(type);
 248       Node val;
 249       do {
 250         val = *te;
 251         ++te;
 252         // Debug("bv-core-model") << "  trying value " << val << "\n";
 253         // Debug("bv-core-model") << "  is in set? " << constants.count(val) << "\n";
 254         // Debug("bv-core-model") << "  enumerator done? " << te.isFinished() << "\n";
 255       } while (constants.count(val) != 0 && !(te.isFinished()));
 256
 257       if (te.isFinished() && constants.count(val) != 0) {
 258         // if we cannot enumerate anymore values we just return the lemma stating that
 259         // at least two of the representatives are equal.
 260         std::vector<TNode> representatives;
 261         representatives.push_back(repr);
 262
 263         for (TNodeSet::const_iterator it = constants_in_eq_engine.begin();
 264              it != constants_in_eq_engine.end(); ++it) {
 265           TNode constant = *it;
 266           if (utils::getSize(constant) == utils::getSize(repr)) {
 267             representatives.push_back(constant);
 268           }
 269         }
 270         for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 271           representatives.push_back(it->first);
 272         }
 273         std::vector<Node> equalities;
 274         for (unsigned i = 0; i < representatives.size(); ++i) {
 275           for (unsigned j = i + 1; j < representatives.size(); ++j) {
 276             TNode a = representatives[i];
 277             TNode b = representatives[j];
 278             if (utils::getSize(a) == utils::getSize(b)) {
 279               equalities.push_back(utils::mkNode(kind::EQUAL, a, b));
 280             }
 281           }
 282         }
 283         Node lemma = utils::mkOr(equalities);
 284         d_bv->lemma(lemma);
 285         Debug("bv-core") << "  lemma: " << lemma << "\n";
 286         return;
 287       }
 288       Debug("bv-core-model") << "   " << repr << " => " << val <<"\n" ;
 289       constants.insert(val);
 290       d_modelValues[repr] = val;
 291     }
 292   }
 293 }
 294
 295 bool CoreSolver::assertFactToEqualityEngine(TNode fact, TNode reason) {
 296   // Notify the equality engine
 297   if (!d_bv->inConflict() && (!d_bv->wasPropagatedBySubtheory(fact) || d_bv->getPropagatingSubtheory(fact) != SUB_CORE)) {
 298     Debug("bv-slicer-eq") << "CoreSolver::assertFactToEqualityEngine fact=" << fact << endl;
 299     // Debug("bv-slicer-eq") << "                     reason=" << reason << endl;
 300     bool negated = fact.getKind() == kind::NOT;
 301     TNode predicate = negated ? fact[0] : fact;
 302     if (predicate.getKind() == kind::EQUAL) {
 303       if (negated) {
 304         // dis-equality
 305         d_equalityEngine.assertEquality(predicate, false, reason);
 306       } else {
 307         // equality
 308         d_equalityEngine.assertEquality(predicate, true, reason);
 309       }
 310     } else {
 311       // Adding predicate if the congruence over it is turned on
 312       if (d_equalityEngine.isFunctionKind(predicate.getKind())) {
 313         d_equalityEngine.assertPredicate(predicate, !negated, reason);
 314       }
 315     }
 316   }
 317
 318   // checking for a conflict
 319   if (d_bv->inConflict()) {
 320     return false;
 321   }
 322   return true;
 323 }
 324
 325 bool CoreSolver::NotifyClass::eqNotifyTriggerEquality(TNode equality, bool value) {
 326   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerEquality(" << equality << ", " << (value ? "true" : "false" )<< ")" << std::endl;
 327   if (value) {
 328     return d_solver.storePropagation(equality);
 329   } else {
 330     return d_solver.storePropagation(equality.notNode());
 331   }
 332 }
 333
 334 bool CoreSolver::NotifyClass::eqNotifyTriggerPredicate(TNode predicate, bool value) {
 335   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerPredicate(" << predicate << ", " << (value ? "true" : "false" ) << ")" << std::endl;
 336   if (value) {
 337     return d_solver.storePropagation(predicate);
 338   } else {
 339     return d_solver.storePropagation(predicate.notNode());
 340   }
 341 }
 342
 343 bool CoreSolver::NotifyClass::eqNotifyTriggerTermEquality(TheoryId tag, TNode t1, TNode t2, bool value) {
 344   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerTermMerge(" << t1 << ", " << t2 << ")" << std::endl;
 345   if (value) {
 346     return d_solver.storePropagation(t1.eqNode(t2));
 347   } else {
 348     return d_solver.storePropagation(t1.eqNode(t2).notNode());
 349   }
 350 }
 351
 352 void CoreSolver::NotifyClass::eqNotifyConstantTermMerge(TNode t1, TNode t2) {
 353   d_solver.conflict(t1, t2);
 354 }
 355
 356 bool CoreSolver::storePropagation(TNode literal) {
 357   return d_bv->storePropagation(literal, SUB_CORE);
 358 }
 359
 360 void CoreSolver::conflict(TNode a, TNode b) {
 361   std::vector<TNode> assumptions;
 362   d_equalityEngine.explainEquality(a, b, true, assumptions);
 363   Node conflict = flattenAnd(assumptions);
 364   d_bv->setConflict(conflict);
 365 }
 366
 367 bool CoreSolver::isCompleteForTerm(TNode term, TNodeBoolMap& seen) {
 368   if (d_useSlicer)
 369     return utils::isCoreTerm(term, seen);
 370
 371   return utils::isEqualityTerm(term, seen);
 372 }
 373
 374 void CoreSolver::collectModelInfo(TheoryModel* m, bool fullModel) {
 375   if (d_useSlicer) {
 376     Unreachable();
 377   }
 378   if (Debug.isOn("bitvector-model")) {
 379     context::CDQueue<Node>::const_iterator it = d_assertionQueue.begin();
 380     for (; it!= d_assertionQueue.end(); ++it) {
 381       Debug("bitvector-model") << "CoreSolver::collectModelInfo (assert "
 382                                << *it << ")\n";
 383     }
 384   }
 385   set<Node> termSet;
 386   d_bv->computeRelevantTerms(termSet);
 387   m->assertEqualityEngine(&d_equalityEngine, &termSet);
 388   if (isComplete()) {
 389     Debug("bitvector-model") << "CoreSolver::collectModelInfo complete.";
 390     for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 391       Node a = it->first;
 392       Node b = it->second;
 393       Debug("bitvector-model") << "CoreSolver::collectModelInfo modelValues "
 394                                << a << " => " << b <<")\n";
 395       m->assertEquality(a, b, true);
 396     }
 397   }
 398 }
 399
 400 Node CoreSolver::getModelValue(TNode var) {
 401   // we don't need to evaluate bv expressions and only look at variable values
 402   // because this only gets called when the core theory is complete (i.e. no other bv
 403   // function symbols are currently asserted)
 404   Assert (d_slicer->isCoreTerm(var));
 405
 406   Debug("bitvector-model") << "CoreSolver::getModelValue (" << var <<")";
 407   Assert (isComplete());
 408   TNode repr = d_equalityEngine.getRepresentative(var);
 409   Node result = Node();
 410   if (repr.getKind() == kind::CONST_BITVECTOR) {
 411     result = repr;
 412   } else if (d_modelValues.find(repr) == d_modelValues.end()) {
 413     // it may be a shared term that never gets asserted
 414     // result is just Null
 415     Assert(d_bv->isSharedTerm(var));
 416   } else {
 417     result = d_modelValues[repr];
 418   }
 419   Debug("bitvector-model") << " => " << result <<"\n";
 420   return result;
 421 }
 422
 423 CoreSolver::Statistics::Statistics()
 424   : d_numCallstoCheck("theory::bv::CoreSolver::NumCallsToCheck", 0)
 425   , d_slicerEnabled("theory::bv::CoreSolver::SlicerEnabled", false)
 426 {
 427   StatisticsRegistry::registerStat(&d_numCallstoCheck);
 428   StatisticsRegistry::registerStat(&d_slicerEnabled);
 429 }
 430 CoreSolver::Statistics::~Statistics() {
 431   StatisticsRegistry::unregisterStat(&d_numCallstoCheck);
 432   StatisticsRegistry::unregisterStat(&d_slicerEnabled);
 433 }