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/********************* */
/*! \file circuit_propagator.h
** \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 A non-clausal circuit propagator for Boolean simplification
**
** A non-clausal circuit propagator for Boolean simplification.
**/
#include "cvc4_private.h"
#ifndef __CVC4__THEORY__BOOLEANS__CIRCUIT_PROPAGATOR_H
#define __CVC4__THEORY__BOOLEANS__CIRCUIT_PROPAGATOR_H
#include <vector>
#include <functional>
#include "theory/theory.h"
#include "context/context.h"
#include "util/hash.h"
#include "expr/node.h"
namespace CVC4 {
namespace theory {
namespace booleans {
/**
* The main purpose of the CircuitPropagator class is to maintain the
* state of the circuit for subsequent calls to propagate(), so that
* the same fact is not output twice, so that the same edge in the
* circuit isn't propagated twice, etc.
*/
class CircuitPropagator {
const std::vector<TNode>& d_atoms;
const std::hash_map<TNode, std::vector<TNode>, TNodeHashFunction>& d_backEdges;
class ConflictException : Exception {
public:
ConflictException() : Exception("A conflict was found in the CircuitPropagator") {
}
};/* class ConflictException */
enum {
ASSIGNMENT_MASK = 1,
IS_ASSIGNED_MASK = 2,
IS_PROPAGATED_FORWARD_MASK = 4,
IS_PROPAGATED_BACKWARD_MASK = 8
};/* enum */
/**
* For each Node we care about, we have a 4-bit state:
* Bit 0 (ASSIGNMENT_MASK) is set to indicate the current assignment
* Bit 1 (IS_ASSIGNED_MASK) is set if a value is assigned
* Bit 2 (IS_PROPAGATED_FORWARD) is set to indicate it's been propagated forward
* Bit 2 (IS_PROPAGATED_BACKWARD) is set to indicate it's been propagated backward
*/
std::hash_map<TNode, unsigned, TNodeHashFunction> d_state;
/** Assign Node in circuit with the value and add it to the changed vector; note conflicts. */
void assign(TNode n, bool b, std::vector<TNode>& changed) {
if(n.getMetaKind() == kind::metakind::CONSTANT) {
bool c = n.getConst<bool>();
if(c != b) {
Debug("circuit-prop") << "while assigning(" << b << "): " << n
<< ", constant conflict" << std::endl;
throw ConflictException();
} else {
Debug("circuit-prop") << "assigning(" << b << "): " << n
<< ", nothing to do" << std::endl;
}
return;
}
unsigned& state = d_state[n];
if((state & IS_ASSIGNED_MASK) != 0) {// if assigned already
if(((state & ASSIGNMENT_MASK) != 0) != b) {// conflict
Debug("circuit-prop") << "while assigning(" << b << "): " << n
<< ", got conflicting assignment(" << assignment(n) << "): "
<< n << std::endl;
throw ConflictException();
} else {
Debug("circuit-prop") << "already assigned(" << b << "): " << n << std::endl;
}
} else {// if unassigned
Debug("circuit-prop") << "assigning(" << b << "): " << n << std::endl;
state |= IS_ASSIGNED_MASK | (b ? ASSIGNMENT_MASK : 0);
changed.push_back(n);
}
}
/** True iff Node is assigned in circuit (either true or false). */
bool isAssigned(TNode n) {
return (d_state[n] & IS_ASSIGNED_MASK) != 0;
}
/** True iff Node is assigned in circuit (either true or false). */
bool isAssigned(TNode n) const {
std::hash_map<TNode, unsigned, TNodeHashFunction>::const_iterator i = d_state.find(n);
return i != d_state.end() && ((*i).second & IS_ASSIGNED_MASK) != 0;
}
/** True iff Node is assigned in circuit with the value given. */
bool isAssignedTo(TNode n, bool b) {
unsigned state = d_state[n];
return (state & IS_ASSIGNED_MASK) &&
(state & ASSIGNMENT_MASK) == (b ? ASSIGNMENT_MASK : 0);
}
/** True iff Node is assigned in circuit (either true or false). */
bool isAssignedTo(TNode n, bool b) const {
std::hash_map<TNode, unsigned, TNodeHashFunction>::const_iterator i = d_state.find(n);
return i != d_state.end() &&
((*i).second & IS_ASSIGNED_MASK) &&
((*i).second & ASSIGNMENT_MASK) == (b ? ASSIGNMENT_MASK : 0);
}
/** Get Node assignment in circuit. Assert-fails if Node is unassigned. */
bool assignment(TNode n) {
unsigned state = d_state[n];
Assert((state & IS_ASSIGNED_MASK) != 0);
return (state & ASSIGNMENT_MASK) != 0;
}
/** Has this node already been propagated forward? */
bool isPropagatedForward(TNode n) {
return (d_state[n] & IS_PROPAGATED_FORWARD_MASK) != 0;
}
/** Has this node already been propagated backward? */
bool isPropagatedBackward(TNode n) {
return (d_state[n] & IS_PROPAGATED_BACKWARD_MASK) != 0;
}
/** Mark this node as already having been propagated forward. */
void setPropagatedForward(TNode n) {
d_state[n] |= IS_PROPAGATED_FORWARD_MASK;
}
/** Mark this node as already having been propagated backward. */
void setPropagatedBackward(TNode n) {
d_state[n] |= IS_PROPAGATED_BACKWARD_MASK;
}
/** Predicate for use in STL functions. */
class IsAssigned : public std::unary_function<TNode, bool> {
CircuitPropagator& d_circuit;
public:
IsAssigned(CircuitPropagator& circuit) :
d_circuit(circuit) {
}
bool operator()(TNode in) const {
return d_circuit.isAssigned(in);
}
};/* class IsAssigned */
/** Predicate for use in STL functions. */
class IsAssignedTo : public std::unary_function<TNode, bool> {
CircuitPropagator& d_circuit;
bool d_value;
public:
IsAssignedTo(CircuitPropagator& circuit, bool value) :
d_circuit(circuit),
d_value(value) {
}
bool operator()(TNode in) const {
return d_circuit.isAssignedTo(in, d_value);
}
};/* class IsAssignedTo */
/**
* Propagate new information (in = polarity) forward in circuit to
* the parents of "in".
*/
void propagateForward(TNode in, bool polarity, std::vector<TNode>& newFacts);
/**
* Propagate new information (in = polarity) backward in circuit to
* the children of "in".
*/
void propagateBackward(TNode in, bool polarity, std::vector<TNode>& newFacts);
public:
/**
* Construct a new CircuitPropagator with the given atoms and backEdges.
*/
CircuitPropagator(const std::vector<TNode>& atoms, const std::hash_map<TNode, std::vector<TNode>, TNodeHashFunction>& backEdges)
: d_atoms(atoms),
d_backEdges(backEdges) {
}
/**
* Propagate new information (in == polarity) through the circuit
* propagator. New information discovered by the propagator are put
* in the (output-only) newFacts vector.
*
* @return true iff conflict found
*/
bool propagate(TNode in, bool polarity, std::vector<Node>& newFacts) CVC4_WARN_UNUSED_RESULT;
};/* class CircuitPropagator */
}/* CVC4::theory::booleans namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
#endif /* __CVC4__THEORY__BOOLEANS__CIRCUIT_PROPAGATOR_H */
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