Example #1
0
WitnessImprovement FCSimplexDecisionProcedure::focusUsingSignDisagreements(ArithVar basic){
  Assert(!d_sgnDisagreements.empty());
  Assert(d_errorSet.focusSize() >= 2);

  if(Debug.isOn("arith::focus")){
    d_errorSet.debugPrint(Debug("arith::focus"));
  }

  ArithVar nb = d_linEq.minBy(d_sgnDisagreements, &LinearEqualityModule::minColLength);
  const Tableau::Entry& e_evar_nb = d_tableau.basicFindEntry(basic, nb);
  int oppositeSgn = - (e_evar_nb.getCoefficient().sgn());
  Debug("arith::focus") << "focusUsingSignDisagreements " << basic << " " << oppositeSgn << endl;

  ArithVarVec dropped;

  Tableau::ColIterator colIter = d_tableau.colIterator(nb);
  for(; !colIter.atEnd(); ++colIter){
    const Tableau::Entry& entry = *colIter;
    Assert(entry.getColVar() == nb);

    int sgn = entry.getCoefficient().sgn();
    Debug("arith::focus")
      << "on row "
      << d_tableau.rowIndexToBasic(entry.getRowIndex())
      << " "
      << entry.getCoefficient() << endl;
    ArithVar currRow = d_tableau.rowIndexToBasic(entry.getRowIndex());
    if(d_errorSet.inError(currRow) && d_errorSet.inFocus(currRow)){
      int errSgn = d_errorSet.getSgn(currRow);

      if(errSgn * sgn == oppositeSgn){
        dropped.push_back(currRow);
        Debug("arith::focus") << "dropping from focus " << currRow << endl;
      }
    }
  }

  d_sgnDisagreements.clear();
  return adjustFocusShrank(dropped);
}
Result::Sat AttemptSolutionSDP::attempt(const ApproximateSimplex::Solution& sol){
  const DenseSet& newBasis = sol.newBasis;
  const DenseMap<DeltaRational>& newValues = sol.newValues;

  DenseSet needsToBeAdded;
  for(DenseSet::const_iterator i = newBasis.begin(), i_end = newBasis.end(); i != i_end; ++i){
    ArithVar b = *i;
    if(!d_tableau.isBasic(b)){
      needsToBeAdded.add(b);
    }
  }
  DenseMap<DeltaRational>::const_iterator nvi = newValues.begin(), nvi_end = newValues.end();
  for(; nvi != nvi_end; ++nvi){
    ArithVar currentlyNb = *nvi;
    if(!d_tableau.isBasic(currentlyNb)){
      if(!matchesNewValue(newValues, currentlyNb)){
        const DeltaRational& newValue = newValues[currentlyNb];
        Trace("arith::updateMany")
          << "updateMany:" << currentlyNb << " "
          << d_variables.getAssignment(currentlyNb) << " to "<< newValue << endl;
        d_linEq.update(currentlyNb, newValue);
        Assert(d_variables.assignmentIsConsistent(currentlyNb));
      }
    }
  }
  d_errorSet.reduceToSignals();
  d_errorSet.setSelectionRule(VAR_ORDER);

  static int instance = 0;
  ++instance;

  if(processSignals()){
    Debug("arith::findModel") << "attemptSolution("<< instance <<") early conflict" << endl;
    d_conflictVariables.purge();
    return Result::UNSAT;
  }else if(d_errorSet.errorEmpty()){
    Debug("arith::findModel") << "attemptSolution("<< instance <<") fixed itself" << endl;
    return Result::SAT;
  }

  while(!needsToBeAdded.empty() && !d_errorSet.errorEmpty()){
    ArithVar toRemove = ARITHVAR_SENTINEL;
    ArithVar toAdd = ARITHVAR_SENTINEL;
    DenseSet::const_iterator i = needsToBeAdded.begin(), i_end = needsToBeAdded.end();
    for(; toAdd == ARITHVAR_SENTINEL && i != i_end; ++i){
      ArithVar v = *i;

      Tableau::ColIterator colIter = d_tableau.colIterator(v);
      for(; !colIter.atEnd(); ++colIter){
        const Tableau::Entry& entry = *colIter;
        Assert(entry.getColVar() == v);
        ArithVar b = d_tableau.rowIndexToBasic(entry.getRowIndex());
        if(!newBasis.isMember(b)){
          toAdd = v;

          bool favorBOverToRemove =
            (toRemove == ARITHVAR_SENTINEL) ||
            (matchesNewValue(newValues, toRemove) && !matchesNewValue(newValues, b)) ||
            (d_tableau.basicRowLength(toRemove) > d_tableau.basicRowLength(b));

          if(favorBOverToRemove){
            toRemove = b;
          }
        }
      }
    }
    Assert(toRemove != ARITHVAR_SENTINEL);
    Assert(toAdd != ARITHVAR_SENTINEL);

    Trace("arith::forceNewBasis") << toRemove << " " << toAdd << endl;
    //Message() << toRemove << " " << toAdd << endl;

    d_linEq.pivotAndUpdate(toRemove, toAdd, newValues[toRemove]);

    Trace("arith::forceNewBasis") << needsToBeAdded.size() << "to go" << endl;
    //Message() << needsToBeAdded.size() << "to go" << endl;
    needsToBeAdded.remove(toAdd);

    bool conflict = processSignals();
    if(conflict){
      d_errorSet.reduceToSignals();
      d_conflictVariables.purge();

      return Result::UNSAT;
    }
  }
  Assert( d_conflictVariables.empty() );

  if(d_errorSet.errorEmpty()){
    return Result::SAT;
  }else{
    d_errorSet.reduceToSignals();
    return Result::SAT_UNKNOWN;
  }
}