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/********************* */
/*! \file theory_bool.cpp
** \verbatim
** Original author: mdeters
** Major contributors: none
** Minor contributors (to current version): none
** This file is part of the CVC4 prototype.
** Copyright (c) 2009, 2010, 2011 The Analysis of Computer Systems Group (ACSys)
** Courant Institute of Mathematical Sciences
** New York University
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief The theory of booleans.
**
** The theory of booleans.
**/
#include "theory/theory.h"
#include "theory/booleans/theory_bool.h"
#include "theory/booleans/circuit_propagator.h"
#include "theory/valuation.h"
#include "util/boolean_simplification.h"
#include <vector>
#include <stack>
#include "util/hash.h"
using namespace std;
namespace CVC4 {
namespace theory {
namespace booleans {
Node TheoryBool::getValue(TNode n) {
NodeManager* nodeManager = NodeManager::currentNM();
switch(n.getKind()) {
case kind::VARIABLE:
// case for Boolean vars is implemented in TheoryEngine (since it
// appeals to the PropEngine to get the value)
Unreachable();
case kind::EQUAL: // 2 args
// should be handled by IFF
Unreachable();
case kind::NOT: // 1 arg
return nodeManager->mkConst(! d_valuation.getValue(n[0]).getConst<bool>());
case kind::AND: { // 2+ args
for(TNode::iterator i = n.begin(),
iend = n.end();
i != iend;
++i) {
if(! d_valuation.getValue(*i).getConst<bool>()) {
return nodeManager->mkConst(false);
}
}
return nodeManager->mkConst(true);
}
case kind::IFF: // 2 args
return nodeManager->mkConst( d_valuation.getValue(n[0]).getConst<bool>() ==
d_valuation.getValue(n[1]).getConst<bool>() );
case kind::IMPLIES: // 2 args
return nodeManager->mkConst( (! d_valuation.getValue(n[0]).getConst<bool>()) ||
d_valuation.getValue(n[1]).getConst<bool>() );
case kind::OR: { // 2+ args
for(TNode::iterator i = n.begin(),
iend = n.end();
i != iend;
++i) {
if(d_valuation.getValue(*i).getConst<bool>()) {
return nodeManager->mkConst(true);
}
}
return nodeManager->mkConst(false);
}
case kind::XOR: // 2 args
return nodeManager->mkConst( d_valuation.getValue(n[0]).getConst<bool>() !=
d_valuation.getValue(n[1]).getConst<bool>() );
case kind::ITE: // 3 args
// all ITEs should be gone except (bool,bool,bool) ones
Assert( n[1].getType() == nodeManager->booleanType() &&
n[2].getType() == nodeManager->booleanType() );
return nodeManager->mkConst( d_valuation.getValue(n[0]).getConst<bool>() ?
d_valuation.getValue(n[1]).getConst<bool>() :
d_valuation.getValue(n[2]).getConst<bool>() );
default:
Unhandled(n.getKind());
}
}
static void
findAtoms(TNode in, vector<TNode>& atoms,
hash_map<TNode, vector<TNode>, TNodeHashFunction>& backEdges) {
Kind k = in.getKind();
Assert(kindToTheoryId(k) == THEORY_BOOL);
stack< pair<TNode, TNode::iterator> > trail;
hash_set<TNode, TNodeHashFunction> seen;
trail.push(make_pair(in, in.begin()));
while(!trail.empty()) {
pair<TNode, TNode::iterator>& pr = trail.top();
Debug("simplify") << "looking at: " << pr.first << endl;
if(pr.second == pr.first.end()) {
trail.pop();
} else {
if(pr.second == pr.first.begin()) {
Debug("simplify") << "first visit: " << pr.first << endl;
// first time we've visited this node?
if(seen.find(pr.first) == seen.end()) {
Debug("simplify") << "+ haven't seen it yet." << endl;
seen.insert(pr.first);
} else {
Debug("simplify") << "+ saw it before." << endl;
trail.pop();
continue;
}
}
TNode n = *pr.second++;
if(seen.find(n) == seen.end()) {
Debug("simplify") << "back edge " << n << " to " << pr.first << endl;
backEdges[n].push_back(pr.first);
Kind nk = n.getKind();
if(kindToTheoryId(nk) == THEORY_BOOL) {
trail.push(make_pair(n, n.begin()));
} else {
Debug("simplify") << "atom: " << n << endl;
atoms.push_back(n);
}
}
}
}
}
Node TheoryBool::simplify(TNode in, Substitutions& outSubstitutions) {
const unsigned prev = outSubstitutions.size();
if(kindToTheoryId(in.getKind()) != THEORY_BOOL) {
Assert(in.getMetaKind() == kind::metakind::VARIABLE &&
in.getType().isBoolean());
return in;
}
// form back edges and atoms
vector<TNode> atoms;
hash_map<TNode, vector<TNode>, TNodeHashFunction> backEdges;
Debug("simplify") << "finding atoms..." << endl << push;
findAtoms(in, atoms, backEdges);
Debug("simplify") << pop << "done finding atoms..." << endl;
hash_map<TNode, Node, TNodeHashFunction> simplified;
vector<Node> newFacts;
CircuitPropagator circuit(atoms, backEdges);
Debug("simplify") << "propagate..." << endl;
if(circuit.propagate(in, true, newFacts)) {
Notice() << "Found a conflict in nonclausal Boolean reasoning" << endl;
return NodeManager::currentNM()->mkConst(false);
}
Debug("simplify") << "done w/ propagate..." << endl;
for(vector<Node>::iterator i = newFacts.begin(), i_end = newFacts.end(); i != i_end; ++i) {
TNode a = *i;
if(a.getKind() == kind::NOT) {
if(a[0].getMetaKind() == kind::metakind::VARIABLE ) {
Debug("simplify") << "found bool unit ~" << a[0] << "..." << endl;
outSubstitutions.push_back(make_pair(a[0], NodeManager::currentNM()->mkConst(false)));
} else if(kindToTheoryId(a[0].getKind()) != THEORY_BOOL) {
Debug("simplify") << "simplifying: " << a << endl;
simplified[a] = d_valuation.simplify(a, outSubstitutions);
Debug("simplify") << "done simplifying, got: " << simplified[a] << endl;
}
} else {
if(a.getMetaKind() == kind::metakind::VARIABLE) {
Debug("simplify") << "found bool unit " << a << "..." << endl;
outSubstitutions.push_back(make_pair(a, NodeManager::currentNM()->mkConst(true)));
} else if(kindToTheoryId(a.getKind()) != THEORY_BOOL) {
Debug("simplify") << "simplifying: " << a << endl;
simplified[a] = d_valuation.simplify(a, outSubstitutions);
Debug("simplify") << "done simplifying, got: " << simplified[a] << endl;
}
}
}
Debug("simplify") << "substituting in root..." << endl;
Node n = in.substitute(outSubstitutions.begin(), outSubstitutions.end());
Debug("simplify") << "got: " << n << endl;
if(Debug.isOn("simplify")) {
Debug("simplify") << "new substitutions:" << endl;
copy(outSubstitutions.begin() + prev, outSubstitutions.end(),
ostream_iterator< pair<TNode, TNode> >(Debug("simplify"), "\n"));
Debug("simplify") << "done." << endl;
}
if(outSubstitutions.size() > prev) {
NodeBuilder<> b(kind::AND);
b << n;
for(Substitutions::iterator i = outSubstitutions.begin() + prev,
i_end = outSubstitutions.end();
i != i_end;
++i) {
if((*i).first.getType().isBoolean()) {
if((*i).second.getMetaKind() == kind::metakind::CONSTANT) {
if((*i).second.getConst<bool>()) {
b << (*i).first;
} else {
b << BooleanSimplification::negate((*i).first);
}
} else {
b << (*i).first.iffNode((*i).second);
}
} else {
b << (*i).first.eqNode((*i).second);
}
}
n = b;
}
Debug("simplify") << "final boolean simplification returned: " << n << endl;
return n;
}
}/* CVC4::theory::booleans namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
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