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/********************* */
/*! \file justification_heuristic.h
** \verbatim
** Original author: Kshitij Bansal
** Major contributors: none
** Minor contributors (to current version): Tim King, Morgan Deters
** This file is part of the CVC4 project.
** Copyright (c) 2009-2013 New York University and The University of Iowa
** See the file COPYING in the top-level source directory for licensing
** information.\endverbatim
**
** \brief Justification heuristic for decision making
**
** A ATGP-inspired justification-based decision heuristic. See
** [insert reference] for more details. This code is, or not, based
** on the CVC3 implementation of the same heuristic.
**
** It needs access to the simplified but non-clausal formula.
**/
#include "cvc4_private.h"
#ifndef __CVC4__DECISION__JUSTIFICATION_HEURISTIC
#define __CVC4__DECISION__JUSTIFICATION_HEURISTIC
#include "decision_engine.h"
#include "decision_strategy.h"
#include "context/cdhashset.h"
#include "context/cdlist.h"
#include "context/cdhashmap.h"
#include "expr/node.h"
#include "prop/sat_solver_types.h"
namespace CVC4 {
namespace decision {
class JustificationHeuristic : public ITEDecisionStrategy {
typedef std::vector<pair<TNode,TNode> > IteList;
typedef context::CDHashMap<TNode,IteList,TNodeHashFunction> IteCache;
typedef context::CDHashMap<TNode,TNode,TNodeHashFunction> SkolemMap;
// being 'justified' is monotonic with respect to decisions
typedef context::CDHashSet<Node,NodeHashFunction> JustifiedSet;
JustifiedSet d_justified;
context::CDO<unsigned> d_prvsIndex;
IntStat d_helfulness;
IntStat d_giveup;
TimerStat d_timestat;
/**
* A copy of the assertions that need to be justified
* directly. Doesn't have ones introduced during during ITE-removal.
*/
context::CDList<TNode> d_assertions;
//TNode is fine since decisionEngine has them too
/** map from ite-rewrite skolem to a boolean-ite assertion */
SkolemMap d_iteAssertions;
// 'key' being TNode is fine since if a skolem didn't exist anywhere,
// we won't look it up. as for 'value', same reason as d_assertions
/** Cache for ITE skolems present in a atomic formula */
IteCache d_iteCache;
/**
* This is used to prevent infinite loop when trying to find a
* splitter. Can happen when exploring assertion corresponding to a
* term-ITE.
*/
hash_set<TNode,TNodeHashFunction> d_visited;
/**
* Set to track visited nodes in a dfs search done in computeITE
* function
*/
hash_set<TNode,TNodeHashFunction> d_visitedComputeITE;
/** current decision for the recursive call */
SatLiteral d_curDecision;
public:
JustificationHeuristic(CVC4::DecisionEngine* de,
context::UserContext *uc,
context::Context *c);
~JustificationHeuristic();
prop::SatLiteral getNext(bool &stopSearch);
void addAssertions(const std::vector<Node> &assertions,
unsigned assertionsEnd,
IteSkolemMap iteSkolemMap);
private:
SatLiteral findSplitter(TNode node, SatValue desiredVal);
/**
* Do all the hard work.
*/
bool findSplitterRec(TNode node, SatValue value);
/* Helper functions */
void setJustified(TNode);
bool checkJustified(TNode);
/* If literal exists corresponding to the node return
that. Otherwise an UNKNOWN */
SatValue tryGetSatValue(Node n);
/* Get list of all term-ITEs for the atomic formula v */
JustificationHeuristic::IteList getITEs(TNode n);
/* Compute all term-ITEs in a node recursively */
void computeITEs(TNode n, IteList &l);
bool handleAndOrEasy(TNode node, SatValue desiredVal);
bool handleAndOrHard(TNode node, SatValue desiredVal);
bool handleBinaryEasy(TNode node1, SatValue desiredVal1,
TNode node2, SatValue desiredVal2);
bool handleBinaryHard(TNode node1, SatValue desiredVal1,
TNode node2, SatValue desiredVal2);
bool handleITE(TNode node, SatValue desiredVal);
bool handleEmbeddedITEs(TNode node);
};/* class JustificationHeuristic */
}/* namespace decision */
}/* namespace CVC4 */
#endif /* __CVC4__DECISION__JUSTIFICATION_HEURISTIC */
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