src/theory/bv/bv_subtheory_core.cpp

   1 /*********************                                                        */
   2 /*! \file bv_subtheory_eq.cpp
   3  ** \verbatim
   4  ** Original author: dejan
   5  ** Major contributors: none
   6  ** Minor contributors (to current version): lianah
   7  ** This file is part of the CVC4 prototype.
   8  ** Copyright (c) 2009-2012  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
  24 using namespace std;
  25 using namespace CVC4;
  26 using namespace CVC4::context;
  27 using namespace CVC4::theory;
  28 using namespace CVC4::theory::bv;
  29 using namespace CVC4::theory::bv::utils;
  30
  31 CoreSolver::CoreSolver(context::Context* c, TheoryBV* bv)
  32   : SubtheorySolver(c, bv),
  33     d_notify(*this),
  34     d_equalityEngine(d_notify, c, "theory::bv::TheoryBV"),
  35     d_slicer(new Slicer(c, this)),
  36     d_isCoreTheory(c, true),
  37     d_reasons(c)
  38 {
  39   if (d_useEqualityEngine) {
  40
  41     // The kinds we are treating as function application in congruence
  42     d_equalityEngine.addFunctionKind(kind::BITVECTOR_CONCAT, true);
  43     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_AND);
  44     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_OR);
  45     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XOR);
  46     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOT);
  47     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NAND);
  48     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NOR);
  49     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_XNOR);
  50     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_COMP);
  51     d_equalityEngine.addFunctionKind(kind::BITVECTOR_MULT, true);
  52     d_equalityEngine.addFunctionKind(kind::BITVECTOR_PLUS, true);
  53     d_equalityEngine.addFunctionKind(kind::BITVECTOR_EXTRACT, true);
  54     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SUB);
  55     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_NEG);
  56     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UDIV);
  57     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UREM);
  58     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SDIV);
  59     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SREM);
  60     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SMOD);
  61     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SHL);
  62     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_LSHR);
  63     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ASHR);
  64     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULT);
  65     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_ULE);
  66     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGT);
  67     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_UGE);
  68     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLT);
  69     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SLE);
  70     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGT);
  71     //    d_equalityEngine.addFunctionKind(kind::BITVECTOR_SGE);
  72   }
  73 }
  74
  75 CoreSolver::~CoreSolver() {
  76   delete d_slicer;
  77 }
  78 void CoreSolver::setMasterEqualityEngine(eq::EqualityEngine* eq) {
  79   d_equalityEngine.setMasterEqualityEngine(eq);
  80 }
  81
  82 void CoreSolver::preRegister(TNode node) {
  83   if (!d_useEqualityEngine)
  84     return;
  85
  86   if (node.getKind() == kind::EQUAL) {
  87       d_equalityEngine.addTriggerEquality(node);
  88       // d_slicer->processEquality(node);
  89   } else {
  90     d_equalityEngine.addTerm(node);
  91   }
  92 }
  93
  94
  95 void CoreSolver::explain(TNode literal, std::vector<TNode>& assumptions) {
  96   bool polarity = literal.getKind() != kind::NOT;
  97   TNode atom = polarity ? literal : literal[0];
  98   if (atom.getKind() == kind::EQUAL) {
  99     d_equalityEngine.explainEquality(atom[0], atom[1], polarity, assumptions);
 100   } else {
 101     d_equalityEngine.explainPredicate(atom, polarity, assumptions);
 102   }
 103 }
 104
 105 Node CoreSolver::getBaseDecomposition(TNode a, std::vector<Node>& explanation) {
 106   std::vector<Node> a_decomp;
 107   d_slicer->getBaseDecomposition(a, a_decomp, explanation);
 108   Node new_a = utils::mkConcat(a_decomp);
 109   Debug("bv-slicer") << "CoreSolver::getBaseDecomposition " << a <<" => " << new_a << "\n";
 110   return new_a;
 111 }
 112
 113 bool CoreSolver::decomposeFact(TNode fact) {
 114   Debug("bv-slicer") << "CoreSolver::decomposeFact fact=" << fact << endl;
 115   // assert decompositions since the equality engine does not know the semantics of
 116   // concat:
 117   //   a == a_1 concat ... concat a_k
 118   //   b == b_1 concat ... concat b_k
 119
 120   if (fact.getKind() == kind::EQUAL) {
 121     TNode a = fact[0];
 122     TNode b = fact[1];
 123
 124     d_slicer->processEquality(fact);
 125     std::vector<Node> explanation;
 126     Node new_a = getBaseDecomposition(a, explanation);
 127     Node new_b = getBaseDecomposition(b, explanation);
 128
 129     explanation.push_back(fact);
 130     Node reason = utils::mkAnd(explanation);
 131     d_reasons.insert(reason);
 132
 133     Assert (utils::getSize(new_a) == utils::getSize(new_b) &&
 134             utils::getSize(new_a) == utils::getSize(a));
 135     // FIXME: do we still need to assert these?
 136     NodeManager* nm = NodeManager::currentNM();
 137     Node a_eq_new_a = nm->mkNode(kind::EQUAL, a, new_a);
 138     Node b_eq_new_b = nm->mkNode(kind::EQUAL, b, new_b);
 139
 140     d_reasons.insert(a_eq_new_a);
 141     d_reasons.insert(b_eq_new_b);
 142
 143     bool ok = true;
 144     ok = assertFactToEqualityEngine(a_eq_new_a, utils::mkTrue());
 145     if (!ok) return false;
 146     ok = assertFactToEqualityEngine(b_eq_new_b, utils::mkTrue());
 147     if (!ok) return false;
 148     // assert the individual equalities as well
 149     //    a_i == b_i
 150     if (new_a.getKind() == kind::BITVECTOR_CONCAT &&
 151         new_b.getKind() == kind::BITVECTOR_CONCAT) {
 152       Assert (new_a.getNumChildren() == new_b.getNumChildren());
 153       for (unsigned i = 0; i < new_a.getNumChildren(); ++i) {
 154         Node eq_i = nm->mkNode(kind::EQUAL, new_a[i], new_b[i]);
 155         ok = assertFactToEqualityEngine(eq_i, reason);
 156         d_reasons.insert(eq_i);
 157         if (!ok) return false;
 158       }
 159     }
 160     // merge the two terms in the slicer as well
 161     d_slicer->assertEquality(fact);
 162   } else {
 163     // still need to register the terms
 164     d_slicer->processEquality(fact[0]);
 165     TNode a = fact[0][0];
 166     TNode b = fact[0][1];
 167     std::vector<Node> explanation_a;
 168     Node new_a = getBaseDecomposition(a, explanation_a);
 169     Node reason_a = explanation_a.empty()? mkTrue() : mkAnd(explanation_a);
 170     assertFactToEqualityEngine(utils::mkNode(kind::EQUAL, a, new_a), reason_a);
 171
 172     std::vector<Node> explanation_b;
 173     Node new_b = getBaseDecomposition(b, explanation_b);
 174     Node reason_b = explanation_b.empty()? mkTrue() : mkAnd(explanation_b);
 175     assertFactToEqualityEngine(utils::mkNode(kind::EQUAL, b, new_b), reason_b);
 176     d_reasons.insert(reason_a);
 177     d_reasons.insert(reason_b);
 178   }
 179   // finally assert the actual fact to the equality engine
 180   return assertFactToEqualityEngine(fact, fact);
 181 }
 182
 183 bool CoreSolver::check(Theory::Effort e) {
 184   Trace("bitvector::core") << "CoreSolver::check \n";
 185   Assert (!d_bv->inConflict());
 186
 187   bool ok = true;
 188   std::vector<Node> core_eqs;
 189   while (! done()) {
 190     TNode fact = get();
 191
 192     // update whether we are in the core fragment
 193     if (d_isCoreTheory && !d_slicer->isCoreTerm(fact)) {
 194       d_isCoreTheory = false;
 195     }
 196
 197     // only reason about equalities
 198     if (fact.getKind() == kind::EQUAL || (fact.getKind() == kind::NOT && fact[0].getKind() == kind::EQUAL)) {
 199       ok = decomposeFact(fact);
 200     } else {
 201       ok = assertFactToEqualityEngine(fact, fact);
 202     }
 203     if (!ok)
 204       return false;
 205   }
 206
 207   // make sure to assert the new splits
 208   std::vector<Node> new_splits;
 209   d_slicer->getNewSplits(new_splits);
 210   for (unsigned i = 0; i < new_splits.size(); ++i) {
 211     ok = assertFactToEqualityEngine(new_splits[i], utils::mkTrue());
 212     if (!ok)
 213       return false;
 214   }
 215   return true;
 216 }
 217
 218 bool CoreSolver::assertFactToEqualityEngine(TNode fact, TNode reason) {
 219   // Notify the equality engine
 220   if (d_useEqualityEngine && !d_bv->inConflict() && !d_bv->propagatedBy(fact, SUB_CORE) ) {
 221     Debug("bv-slicer-eq") << "CoreSolver::assertFactToEqualityEngine fact=" << fact << endl;
 222     // Debug("bv-slicer-eq") << "                     reason=" << reason << endl;
 223     bool negated = fact.getKind() == kind::NOT;
 224     TNode predicate = negated ? fact[0] : fact;
 225     if (predicate.getKind() == kind::EQUAL) {
 226       if (negated) {
 227         // dis-equality
 228         d_equalityEngine.assertEquality(predicate, false, reason);
 229       } else {
 230         // equality
 231         d_equalityEngine.assertEquality(predicate, true, reason);
 232       }
 233     } else {
 234       // Adding predicate if the congruence over it is turned on
 235       if (d_equalityEngine.isFunctionKind(predicate.getKind())) {
 236         d_equalityEngine.assertPredicate(predicate, !negated, reason);
 237       }
 238     }
 239   }
 240
 241   // checking for a conflict
 242   if (d_bv->inConflict()) {
 243     return false;
 244   }
 245   return true;
 246 }
 247
 248 bool CoreSolver::NotifyClass::eqNotifyTriggerEquality(TNode equality, bool value) {
 249   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerEquality(" << equality << ", " << (value ? "true" : "false" )<< ")" << std::endl;
 250   if (value) {
 251     return d_solver.storePropagation(equality);
 252   } else {
 253     return d_solver.storePropagation(equality.notNode());
 254   }
 255 }
 256
 257 bool CoreSolver::NotifyClass::eqNotifyTriggerPredicate(TNode predicate, bool value) {
 258   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerPredicate(" << predicate << ", " << (value ? "true" : "false" ) << ")" << std::endl;
 259   if (value) {
 260     return d_solver.storePropagation(predicate);
 261   } else {
 262     return d_solver.storePropagation(predicate.notNode());
 263   }
 264 }
 265
 266 bool CoreSolver::NotifyClass::eqNotifyTriggerTermEquality(TheoryId tag, TNode t1, TNode t2, bool value) {
 267   Debug("bitvector::core") << "NotifyClass::eqNotifyTriggerTermMerge(" << t1 << ", " << t2 << ")" << std::endl;
 268   if (value) {
 269     return d_solver.storePropagation(t1.eqNode(t2));
 270   } else {
 271     return d_solver.storePropagation(t1.eqNode(t2).notNode());
 272   }
 273 }
 274
 275 void CoreSolver::NotifyClass::eqNotifyConstantTermMerge(TNode t1, TNode t2) {
 276   d_solver.conflict(t1, t2);
 277 }
 278
 279 bool CoreSolver::storePropagation(TNode literal) {
 280   return d_bv->storePropagation(literal, SUB_CORE);
 281 }
 282
 283 void CoreSolver::conflict(TNode a, TNode b) {
 284   std::vector<TNode> assumptions;
 285   d_equalityEngine.explainEquality(a, b, true, assumptions);
 286   d_bv->setConflict(mkAnd(assumptions));
 287 }
 288
 289 void CoreSolver::collectModelInfo(TheoryModel* m) {
 290   if (Debug.isOn("bitvector-model")) {
 291     context::CDQueue<Node>::const_iterator it = d_assertionQueue.begin();
 292     for (; it!= d_assertionQueue.end(); ++it) {
 293       Debug("bitvector-model") << "CoreSolver::collectModelInfo (assert "
 294                                << *it << ")\n";
 295     }
 296   }
 297   set<Node> termSet;
 298   d_bv->computeRelevantTerms(termSet);
 299   m->assertEqualityEngine(&d_equalityEngine, &termSet);
 300 }