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/********************* */
/*! \file justification_heuristic.h
** \verbatim
** Original author: kshitij
** Major contributors: none
** Minor contributors (to current version): mdeters
** This file is part of the CVC4 prototype.
** Copyright (c) 2009-2012 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 "expr/node.h"
#include "prop/sat_solver_types.h"
namespace CVC4 {
namespace decision {
class GiveUpException : public Exception {
public:
GiveUpException() :
Exception("justification heuristic: giving up") {
}
};/* class GiveUpException */
class JustificationHeuristic : public ITEDecisionStrategy {
typedef std::vector<pair<TNode,TNode> > IteList;
typedef hash_map<TNode,IteList,TNodeHashFunction> IteCache;
typedef hash_map<TNode,TNode,TNodeHashFunction> SkolemMap;
// being 'justified' is monotonic with respect to decisions
typedef context::CDHashSet<TNode,TNodeHashFunction> 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.
*/
std::vector<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;
public:
JustificationHeuristic(CVC4::DecisionEngine* de, context::Context *c):
ITEDecisionStrategy(de, c),
d_justified(c),
d_prvsIndex(c, 0),
d_helfulness("decision::jh::helpfulness", 0),
d_giveup("decision::jh::giveup", 0),
d_timestat("decision::jh::time") {
StatisticsRegistry::registerStat(&d_helfulness);
StatisticsRegistry::registerStat(&d_giveup);
StatisticsRegistry::registerStat(&d_timestat);
Trace("decision") << "Justification heuristic enabled" << std::endl;
}
~JustificationHeuristic() {
StatisticsRegistry::unregisterStat(&d_helfulness);
StatisticsRegistry::unregisterStat(&d_timestat);
}
prop::SatLiteral getNext(bool &stopSearch) {
Trace("decision") << "JustificationHeuristic::getNext()" << std::endl;
TimerStat::CodeTimer codeTimer(d_timestat);
d_visited.clear();
if(Trace.isOn("justified")) {
for(JustifiedSet::iterator i = d_justified.begin();
i != d_justified.end(); ++i) {
TNode n = *i;
SatLiteral l = d_decisionEngine->hasSatLiteral(n) ?
d_decisionEngine->getSatLiteral(n) : -1;
SatValue v = tryGetSatValue(n);
Trace("justified") <<"{ "<<l<<"}" << n <<": "<<v << std::endl;
}
}
for(unsigned i = d_prvsIndex; i < d_assertions.size(); ++i) {
Debug("decision") << "---" << std::endl << d_assertions[i] << std::endl;
// Sanity check: if it was false, aren't we inconsistent?
Assert( tryGetSatValue(d_assertions[i]) != SAT_VALUE_FALSE);
SatValue desiredVal = SAT_VALUE_TRUE;
SatLiteral litDecision;
try {
litDecision = findSplitter(d_assertions[i], desiredVal);
}catch(GiveUpException &e) {
return prop::undefSatLiteral;
}
if(litDecision != undefSatLiteral)
return litDecision;
}
Trace("decision") << "jh: Nothing to split on " << std::endl;
#if defined CVC4_ASSERTIONS || defined CVC4_DEBUG
bool alljustified = true;
for(unsigned i = 0 ; i < d_assertions.size() && alljustified ; ++i) {
TNode curass = d_assertions[i];
while(curass.getKind() == kind::NOT)
curass = curass[0];
alljustified &= checkJustified(curass);
if(Debug.isOn("decision")) {
if(!checkJustified(curass))
Debug("decision") << "****** Not justified [i="<<i<<"]: "
<< d_assertions[i] << std::endl;
}
}
Assert(alljustified);
#endif
// SAT solver can stop...
stopSearch = true;
d_decisionEngine->setResult(SAT_VALUE_TRUE);
return prop::undefSatLiteral;
}
void addAssertions(const std::vector<Node> &assertions,
unsigned assertionsEnd,
IteSkolemMap iteSkolemMap) {
Trace("decision")
<< "JustificationHeuristic::addAssertions()"
<< " size = " << assertions.size()
<< " assertionsEnd = " << assertionsEnd
<< std::endl;
// Save the 'real' assertions locally
for(unsigned i = 0; i < assertionsEnd; ++i)
d_assertions.push_back(assertions[i]);
// Save mapping between ite skolems and ite assertions
for(IteSkolemMap::iterator i = iteSkolemMap.begin();
i != iteSkolemMap.end(); ++i) {
Trace("jh-ite") << " jh-ite: " << (i->first) << " maps to "
<< assertions[(i->second)] << std::endl;
Assert(i->second >= assertionsEnd && i->second < assertions.size());
d_iteAssertions[i->first] = assertions[i->second];
}
}
/* Compute justified */
/*bool computeJustified() {
}*/
private:
SatLiteral findSplitter(TNode node, SatValue desiredVal)
{
bool ret;
SatLiteral litDecision;
ret = findSplitterRec(node, desiredVal, &litDecision);
if(ret == true) {
Debug("decision") << "Yippee!!" << std::endl;
//d_prvsIndex = i;
++d_helfulness;
return litDecision;
} else {
return undefSatLiteral;
}
}
/**
* Do all the hard work.
* @param findFirst returns
*/
bool findSplitterRec(TNode node, SatValue value, SatLiteral* litDecision);
/* 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 */
const JustificationHeuristic::IteList& getITEs(TNode n);
/* Compute all term-ITEs in a node recursively */
void computeITEs(TNode n, IteList &l);
};/* class JustificationHeuristic */
}/* namespace decision */
}/* namespace CVC4 */
#endif /* __CVC4__DECISION__JUSTIFICATION_HEURISTIC */
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