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/******************************************************************************
* Top contributors (to current version):
* Kshitij Bansal, Gereon Kremer, Andres Noetzli
*
* This file is part of the cvc5 project.
*
* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
* in the top-level source directory and their institutional affiliations.
* All rights reserved. See the file COPYING in the top-level source
* directory for licensing information.
* ****************************************************************************
*
* 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 "cvc5_private.h"
#ifndef CVC5__DECISION__JUSTIFICATION_HEURISTIC
#define CVC5__DECISION__JUSTIFICATION_HEURISTIC
#include <unordered_set>
#include <utility>
#include "context/cdhashmap.h"
#include "context/cdhashset.h"
#include "context/cdlist.h"
#include "context/cdo.h"
#include "decision/decision_strategy.h"
#include "expr/node.h"
#include "options/decision_weight.h"
#include "prop/sat_solver_types.h"
#include "util/statistics_stats.h"
namespace cvc5 {
namespace decision {
class JustificationHeuristic : public ITEDecisionStrategy {
// TRUE FALSE MEH
enum SearchResult {FOUND_SPLITTER, NO_SPLITTER, DONT_KNOW};
typedef std::vector<std::pair<Node, Node> > SkolemList;
typedef context::CDHashMap<Node, SkolemList, NodeHashFunction> SkolemCache;
typedef std::vector<Node> ChildList;
typedef context::
CDHashMap<Node, std::pair<ChildList, ChildList>, NodeHashFunction>
ChildCache;
typedef context::CDHashMap<Node,Node,NodeHashFunction> SkolemMap;
typedef context::CDHashMap<Node,
std::pair<DecisionWeight, DecisionWeight>,
NodeHashFunction>
WeightCache;
// being 'justified' is monotonic with respect to decisions
typedef context::CDHashSet<Node,NodeHashFunction> JustifiedSet;
JustifiedSet d_justified;
typedef context::CDHashMap<Node,DecisionWeight,NodeHashFunction> ExploredThreshold;
ExploredThreshold d_exploredThreshold;
context::CDO<unsigned> d_prvsIndex;
context::CDO<unsigned> d_threshPrvsIndex;
IntStat d_helpfulness;
IntStat d_giveup;
TimerStat d_timestat;
/**
* A copy of the assertions that need to be justified
* directly. Doesn't have ones introduced during during term removal.
*/
context::CDList<Node> d_assertions;
/** map from skolems introduced in term removal to the corresponding assertion
*/
SkolemMap d_skolemAssertions;
/** Cache for skolems present in a atomic formula */
SkolemCache d_skolemCache;
/**
* This is used to prevent infinite loop when trying to find a
* splitter. Can happen when exploring assertion corresponding to a
* term-ITE.
*/
std::unordered_set<Node,NodeHashFunction> d_visited;
/**
* Set to track visited nodes in a dfs search done in computeSkolems
* function
*/
std::unordered_set<Node, NodeHashFunction> d_visitedComputeSkolems;
/** current decision for the recursive call */
prop::SatLiteral d_curDecision;
/** current threshold for the recursive call */
DecisionWeight d_curThreshold;
/** child cache */
ChildCache d_childCache;
/** computed polarized weight cache */
WeightCache d_weightCache;
class myCompareClass {
JustificationHeuristic* d_jh;
bool d_b;
public:
myCompareClass(JustificationHeuristic* jh, bool b):d_jh(jh),d_b(b) {};
bool operator() (TNode n1, TNode n2) {
return d_jh->getWeightPolarized(n1, d_b) < d_jh->getWeightPolarized(n2, d_b);
}
};
public:
JustificationHeuristic(DecisionEngineOld* de,
context::UserContext* uc,
context::Context* c);
~JustificationHeuristic();
prop::SatLiteral getNext(bool& stopSearch) override;
/**
* Notify this class that assertion is an (input) assertion, not corresponding
* to a skolem definition.
*/
void addAssertion(TNode assertion) override;
/**
* Notify this class that lem is the skolem definition for skolem, which is
* a part of the current assertions.
*/
void addSkolemDefinition(TNode lem, TNode skolem) override;
private:
/* getNext with an option to specify threshold */
prop::SatLiteral getNextThresh(bool& stopSearch, DecisionWeight threshold);
prop::SatLiteral findSplitter(TNode node, prop::SatValue desiredVal);
/**
* Do all the hard work.
*/
SearchResult findSplitterRec(TNode node, prop::SatValue value);
/* Helper functions */
void setJustified(TNode);
bool checkJustified(TNode);
DecisionWeight getExploredThreshold(TNode);
void setExploredThreshold(TNode);
void setPrvsIndex(int);
int getPrvsIndex();
DecisionWeight getWeightPolarized(TNode n, bool polarity);
DecisionWeight getWeightPolarized(TNode n, prop::SatValue);
static DecisionWeight getWeight(TNode);
bool compareByWeightFalse(TNode, TNode);
bool compareByWeightTrue(TNode, TNode);
TNode getChildByWeight(TNode n, int i, bool polarity);
/* If literal exists corresponding to the node return
that. Otherwise an UNKNOWN */
prop::SatValue tryGetSatValue(Node n);
/* Get list of all term-ITEs for the atomic formula v */
JustificationHeuristic::SkolemList getSkolems(TNode n);
/**
* For big and/or nodes, a cache to save starting index into children
* for efficiently.
*/
typedef context::CDHashMap<Node, int, NodeHashFunction> StartIndexCache;
StartIndexCache d_startIndexCache;
int getStartIndex(TNode node);
void saveStartIndex(TNode node, int val);
/* Compute all term-removal skolems in a node recursively */
void computeSkolems(TNode n, SkolemList& l);
SearchResult handleAndOrEasy(TNode node, prop::SatValue desiredVal);
SearchResult handleAndOrHard(TNode node, prop::SatValue desiredVal);
SearchResult handleBinaryEasy(TNode node1,
prop::SatValue desiredVal1,
TNode node2,
prop::SatValue desiredVal2);
SearchResult handleBinaryHard(TNode node1,
prop::SatValue desiredVal1,
TNode node2,
prop::SatValue desiredVal2);
SearchResult handleITE(TNode node, prop::SatValue desiredVal);
SearchResult handleEmbeddedSkolems(TNode node);
};/* class JustificationHeuristic */
}/* namespace decision */
} // namespace cvc5
#endif /* CVC5__DECISION__JUSTIFICATION_HEURISTIC */
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