src/theory/bv/bv_subtheory_core.cpp

   1 /*********************                                                        */
   2 /*! \file bv_subtheory_core.cpp
   3  ** \verbatim
   4  ** Original author: Liana Hadarean
   5  ** Major contributors: lianah
   6  ** Minor contributors (to current version): none
   7  ** This file is part of the CVC4 project.
   8  ** Copyright (c) 2009-2013  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/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"),
  36     d_slicer(new Slicer()),
  37     d_isCoreTheory(c, true),
  38     d_reasons(c)
  39 {
  40   if (d_useEqualityEngine) {
  41
  42     // The kinds we are treating as function application in congruence
  43     d_equalityEngine.addFunctionKind(kind::BITVECTOR_CONCAT, true);
  44     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_AND);
  45     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_OR);
  46     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XOR);
  47     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOT);
  48     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NAND);
  49     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOR);
  50     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XNOR);
  51     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_COMP);
  52     d_equalityEngine.addFunctionKind(kind::BITVECTOR_MULT, true);
  53     d_equalityEngine.addFunctionKind(kind::BITVECTOR_PLUS, true);
  54     d_equalityEngine.addFunctionKind(kind::BITVECTOR_EXTRACT, true);
  55     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SUB);
  56     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NEG);
  57     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UDIV);
  58     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UREM);
  59     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SDIV);
  60     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SREM);
  61     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SMOD);
  62     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SHL);
  63     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_LSHR);
  64     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ASHR);
  65     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULT);
  66     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULE);
  67     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGT);
  68     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGE);
  69     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLT);
  70     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLE);
  71     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGT);
  72     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGE);
  73   }
  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::preRegister(TNode node) {
  84   if (!d_useEqualityEngine)
  85     return;
  86
  87   if (node.getKind() == kind::EQUAL) {
  88       d_equalityEngine.addTriggerEquality(node);
  89       if (options::bitvectorCoreSolver()) {
  90         d_slicer->processEquality(node);
  91       }
  92   } else {
  93     d_equalityEngine.addTerm(node);
  94   }
  95 }
  96
  97
  98 void CoreSolver::explain(TNode literal, std::vector<TNode>& assumptions) {
  99   bool polarity = literal.getKind() != kind::NOT;
 100   TNode atom = polarity ? literal : literal[0];
 101   if (atom.getKind() == kind::EQUAL) {
 102     d_equalityEngine.explainEquality(atom[0], atom[1], polarity, assumptions);
 103   } else {
 104     d_equalityEngine.explainPredicate(atom, polarity, assumptions);
 105   }
 106 }
 107
 108 Node CoreSolver::getBaseDecomposition(TNode a) {
 109   std::vector<Node> a_decomp;
 110   d_slicer->getBaseDecomposition(a, a_decomp);
 111   Node new_a = utils::mkConcat(a_decomp);
 112   Debug("bv-slicer") << "CoreSolver::getBaseDecomposition " << a <<" => " << new_a << "\n";
 113   return new_a;
 114 }
 115
 116 bool CoreSolver::decomposeFact(TNode fact) {
 117   Debug("bv-slicer") << "CoreSolver::decomposeFact fact=" << fact << endl;
 118   // assert decompositions since the equality engine does not know the semantics of
 119   // concat:
 120   //   a == a_1 concat ... concat a_k
 121   //   b == b_1 concat ... concat b_k
 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   Assert (!d_bv->inConflict());
 170   ++(d_statistics.d_numCallstoCheck);
 171   bool ok = true;
 172   std::vector<Node> core_eqs;
 173   while (! done()) {
 174     TNode fact = get();
 175
 176     // update whether we are in the core fragment
 177     if (d_isCoreTheory && !d_slicer->isCoreTerm(fact)) {
 178       d_isCoreTheory = false;
 179     }
 180
 181     // only reason about equalities
 182     if (fact.getKind() == kind::EQUAL || (fact.getKind() == kind::NOT && fact[0].getKind() == kind::EQUAL)) {
 183       if (options::bitvectorCoreSolver()) {
 184         ok = decomposeFact(fact);
 185       } else {
 186         ok = assertFactToEqualityEngine(fact, fact);
 187       }
 188     } else {
 189       ok = assertFactToEqualityEngine(fact, fact);
 190     }
 191     if (!ok)
 192       return false;
 193   }
 194
 195   if (Theory::fullEffort(e) && isComplete()) {
 196     buildModel();
 197   }
 198
 199   return true;
 200 }
 201
 202 void CoreSolver::buildModel() {
 203   if (options::bitvectorCoreSolver()) {
 204     // FIXME
 205     Unreachable();
 206     return;
 207   }
 208   Debug("bv-core") << "CoreSolver::buildModel() \n";
 209   d_modelValues.clear();
 210   TNodeSet constants;
 211   TNodeSet constants_in_eq_engine;
 212   // collect constants in equality engine
 213   eq::EqClassesIterator eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 214   while (!eqcs_i.isFinished()) {
 215     TNode repr = *eqcs_i;
 216     if  (repr.getKind() == kind::CONST_BITVECTOR) {
 217       // must check if it's just the constant
 218       eq::EqClassIterator it(repr, &d_equalityEngine);
 219       if (!(++it).isFinished() || true) {
 220         constants.insert(repr);
 221         constants_in_eq_engine.insert(repr);
 222       }
 223     }
 224     ++eqcs_i;
 225   }
 226   // build repr to value map
 227
 228   eqcs_i = eq::EqClassesIterator(&d_equalityEngine);
 229   while (!eqcs_i.isFinished()) {
 230     TNode repr = *eqcs_i;
 231     ++eqcs_i;
 232
 233     if (repr.getKind() != kind::VARIABLE &&
 234         repr.getKind() != kind::SKOLEM &&
 235         repr.getKind() != kind::CONST_BITVECTOR &&
 236         !d_bv->isSharedTerm(repr)) {
 237       continue;
 238     }
 239
 240     TypeNode type = repr.getType();
 241     if (type.isBitVector() && repr.getKind()!= kind::CONST_BITVECTOR) {
 242       Debug("bv-core-model") << "   processing " << repr <<"\n";
 243       // we need to assign a value for it
 244       TypeEnumerator te(type);
 245       Node val;
 246       do {
 247         val = *te;
 248         ++te;
 249         // Debug("bv-core-model") << "  trying value " << val << "\n";
 250         // Debug("bv-core-model") << "  is in set? " << constants.count(val) << "\n";
 251         // Debug("bv-core-model") << "  enumerator done? " << te.isFinished() << "\n";
 252       } while (constants.count(val) != 0 && !(te.isFinished()));
 253
 254       if (te.isFinished() && constants.count(val) != 0) {
 255         // if we cannot enumerate anymore values we just return the lemma stating that
 256         // at least two of the representatives are equal.
 257         std::vector<TNode> representatives;
 258         representatives.push_back(repr);
 259
 260         for (TNodeSet::const_iterator it = constants_in_eq_engine.begin();
 261              it != constants_in_eq_engine.end(); ++it) {
 262           TNode constant = *it;
 263           if (utils::getSize(constant) == utils::getSize(repr)) {
 264             representatives.push_back(constant);
 265           }
 266         }
 267         for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 268           representatives.push_back(it->first);
 269         }
 270         std::vector<Node> equalities;
 271         for (unsigned i = 0; i < representatives.size(); ++i) {
 272           for (unsigned j = i + 1; j < representatives.size(); ++j) {
 273             TNode a = representatives[i];
 274             TNode b = representatives[j];
 275             if (utils::getSize(a) == utils::getSize(b)) {
 276               equalities.push_back(utils::mkNode(kind::EQUAL, a, b));
 277             }
 278           }
 279         }
 280         Node lemma = utils::mkOr(equalities);
 281         d_bv->lemma(lemma);
 282         Debug("bv-core") << "  lemma: " << lemma << "\n";
 283         return;
 284       }
 285       Debug("bv-core-model") << "   " << repr << " => " << val <<"\n" ;
 286       constants.insert(val);
 287       d_modelValues[repr] = val;
 288     }
 289   }
 290 }
 291
 292 bool CoreSolver::assertFactToEqualityEngine(TNode fact, TNode reason) {
 293   // Notify the equality engine
 294   if (d_useEqualityEngine && !d_bv->inConflict() && (!d_bv->wasPropagatedBySubtheory(fact) || !d_bv->getPropagatingSubtheory(fact) == SUB_CORE)) {
 295     Debug("bv-slicer-eq") << "CoreSolver::assertFactToEqualityEngine fact=" << fact << endl;
 296     // Debug("bv-slicer-eq") << "                     reason=" << reason << endl;
 297     bool negated = fact.getKind() == kind::NOT;
 298     TNode predicate = negated ? fact[0] : fact;
 299     if (predicate.getKind() == kind::EQUAL) {
 300       if (negated) {
 301         // dis-equality
 302         d_equalityEngine.assertEquality(predicate, false, reason);
 303       } else {
 304         // equality
 305         d_equalityEngine.assertEquality(predicate, true, reason);
 306       }
 307     } else {
 308       // Adding predicate if the congruence over it is turned on
 309       if (d_equalityEngine.isFunctionKind(predicate.getKind())) {
 310         d_equalityEngine.assertPredicate(predicate, !negated, reason);
 311       }
 312     }
 313   }
 314
 315   // checking for a conflict
 316   if (d_bv->inConflict()) {
 317     return false;
 318   }
 319   return true;
 320 }
 321
 322 bool CoreSolver::NotifyClass::eqNotifyTriggerEquality(TNode equality, bool value) {
 323   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerEquality(" << equality << ", " << (value ? "true" : "false" )<< ")" << std::endl;
 324   if (value) {
 325     return d_solver.storePropagation(equality);
 326   } else {
 327     return d_solver.storePropagation(equality.notNode());
 328   }
 329 }
 330
 331 bool CoreSolver::NotifyClass::eqNotifyTriggerPredicate(TNode predicate, bool value) {
 332   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerPredicate(" << predicate << ", " << (value ? "true" : "false" ) << ")" << std::endl;
 333   if (value) {
 334     return d_solver.storePropagation(predicate);
 335   } else {
 336     return d_solver.storePropagation(predicate.notNode());
 337   }
 338 }
 339
 340 bool CoreSolver::NotifyClass::eqNotifyTriggerTermEquality(TheoryId tag, TNode t1, TNode t2, bool value) {
 341   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerTermMerge(" << t1 << ", " << t2 << ")" << std::endl;
 342   if (value) {
 343     return d_solver.storePropagation(t1.eqNode(t2));
 344   } else {
 345     return d_solver.storePropagation(t1.eqNode(t2).notNode());
 346   }
 347 }
 348
 349 void CoreSolver::NotifyClass::eqNotifyConstantTermMerge(TNode t1, TNode t2) {
 350   d_solver.conflict(t1, t2);
 351 }
 352
 353 bool CoreSolver::storePropagation(TNode literal) {
 354   return d_bv->storePropagation(literal, SUB_CORE);
 355 }
 356
 357 void CoreSolver::conflict(TNode a, TNode b) {
 358   std::vector<TNode> assumptions;
 359   d_equalityEngine.explainEquality(a, b, true, assumptions);
 360   Node conflict = flattenAnd(assumptions);
 361   d_bv->setConflict(conflict);
 362 }
 363
 364 void CoreSolver::collectModelInfo(TheoryModel* m) {
 365   if (options::bitvectorCoreSolver()) {
 366     Unreachable();
 367     return;
 368   }
 369   if (Debug.isOn("bitvector-model")) {
 370     context::CDQueue<Node>::const_iterator it = d_assertionQueue.begin();
 371     for (; it!= d_assertionQueue.end(); ++it) {
 372       Debug("bitvector-model") << "CoreSolver::collectModelInfo (assert "
 373                                << *it << ")\n";
 374     }
 375   }
 376   set<Node> termSet;
 377   d_bv->computeRelevantTerms(termSet);
 378   m->assertEqualityEngine(&d_equalityEngine, &termSet);
 379   if (isComplete()) {
 380     Debug("bitvector-model") << "CoreSolver::collectModelInfo complete.";
 381     for (ModelValue::const_iterator it = d_modelValues.begin(); it != d_modelValues.end(); ++it) {
 382       Node a = it->first;
 383       Node b = it->second;
 384       m->assertEquality(a, b, true);
 385     }
 386   }
 387 }
 388
 389 Node CoreSolver::getModelValue(TNode var) {
 390   // we don't need to evaluate bv expressions and only look at variable values
 391   // because this only gets called when the core theory is complete (i.e. no other bv
 392   // function symbols are currently asserted)
 393   Assert (d_slicer->isCoreTerm(var));
 394
 395   Debug("bitvector-model") << "CoreSolver::getModelValue (" << var <<")";
 396   Assert (isComplete());
 397   TNode repr = d_equalityEngine.getRepresentative(var);
 398   Node result = Node();
 399   if (repr.getKind() == kind::CONST_BITVECTOR) {
 400     result = repr;
 401   } else if (d_modelValues.find(repr) == d_modelValues.end()) {
 402     // it may be a shared term that never gets asserted
 403     // result is just Null
 404     Assert(d_bv->isSharedTerm(var));
 405   } else {
 406     result = d_modelValues[repr];
 407   }
 408   Debug("bitvector-model") << " => " << result <<"\n";
 409   return result;
 410 }
 411
 412 CoreSolver::Statistics::Statistics()
 413   : d_numCallstoCheck("theory::bv::CoreSolver::NumCallsToCheck", 0)
 414 {
 415   StatisticsRegistry::registerStat(&d_numCallstoCheck);
 416 }
 417 CoreSolver::Statistics::~Statistics() {
 418   StatisticsRegistry::unregisterStat(&d_numCallstoCheck);
 419 }