org.sat4j.minisat.core
Class Solver<D extends DataStructureFactory>

java.lang.Object
  org.sat4j.minisat.core.Solver<D>

All Implemented Interfaces:

Serializable, ICDCL<D>, Learner, UnitPropagationListener, IProblem, ISolver, ISolverService

public class Solver<D extends DataStructureFactory>
extends Object
implements ISolverService, ICDCL<D>

The backbone of the library providing the modular implementation of a MiniSAT (Chaff) like solver.

Author:

leberre

See Also:

Serialized Form

Field Summary

protected IVec<Constr>	constrs Set of original constraints.
protected D	dsfactory
ISimplifier	EXPENSIVE_SIMPLIFICATION
ISimplifier	EXPENSIVE_SIMPLIFICATION_WLONLY
LearnedConstraintsDeletionStrategy	glucose
protected LearnedConstraintsDeletionStrategy	learnedConstraintsDeletionStrategy
protected IVec<Constr>	learnts Set of learned constraints.
LearnedConstraintsDeletionStrategy	memory_based
static ISimplifier	NO_SIMPLIFICATION
protected ICDCLLogger	out
protected int	rootLevel S?
ISimplifier	SIMPLE_SIMPLIFICATION
protected SearchListener	slistener
protected IVecInt	trail affectation en ordre chronologique
protected IVecInt	trailLim indice des s?
protected boolean	undertimeout
protected ILits	voc

Constructor Summary

Solver(LearningStrategy<D> learner, D dsf, IOrder order, RestartStrategy restarter)
creates a Solver without LearningListener.

Solver(LearningStrategy<D> learner, D dsf, SearchParams params, IOrder order, RestartStrategy restarter)

Solver(LearningStrategy<D> learner, D dsf, SearchParams params, IOrder order, RestartStrategy restarter, ICDCLLogger logger)

Method Summary

void	addAllClauses(IVec<IVecInt> clauses) Create clauses from a set of set of literals.
IConstr	addAtLeast(IVecInt literals, int degree) Create a cardinality constraint of the type "at least n of those literals must be satisfied"
IConstr	addAtMost(IVecInt literals, int degree) Create a cardinality constraint of the type "at most n of those literals must be satisfied"
IConstr	addBlockingClause(IVecInt literals) Add a clause in order to prevent an assignment to occur.
void	addClause(int[] literals) Add a new clause in the SAT solver.
IConstr	addClause(IVecInt literals) Create a clause from a set of literals The literals are represented by non null integers such that opposite literals a represented by opposite values.
protected IConstr	addConstr(Constr constr)
IConstr	addExactly(IVecInt literals, int n) Create a cardinality constraint of the type "exactly n of those literals must be satisfied".
void	analyze(Constr confl, Pair results)
protected void	analyzeAtRootLevel(Constr conflict)
IVecInt	analyzeFinalConflictInTermsOfAssumptions(Constr confl, IVecInt assumps, int conflictingLiteral) Derive a subset of the assumptions causing the inconistency.
boolean	assume(int p)
void	backtrack(int[] reason) Ask the SAT solver to backtrack.
protected void	cancelUntil(int level) Cancel several levels of assumptions
void	claBumpActivity(Constr confl) Propagate activity to a constraint
void	clearLearntClauses() Remove clauses learned during the solving process.
int	currentDecisionLevel() To access the current decision level
protected void	decayActivities()
int	decisionLevel()
protected IVecInt	dimacs2internal(IVecInt in)
boolean	enqueue(int p) satisfies a literal
boolean	enqueue(int p, Constr from) satisfies a literal
void	expireTimeout() Expire the timeout of the solver.
int[]	findModel() Look for a model satisfying all the clauses available in the problem.
int[]	findModel(IVecInt assumps) Look for a model satisfying all the clauses available in the problem.
LearnedConstraintsDeletionStrategy	fixedSize(int maxsize)
DataStructureFactory	getDSFactory()
IConstr	getIthConstr(int i) returns the ith constraint in the solver.
IVec<Constr>	getLearnedConstraints() Read-Only access to the list of constraints learned and not deleted so far in the solver.
int[]	getLiteralsPropagatedAt(int decisionLevel) To access the literals propagated at a specific decision level.
ICDCLLogger	getLogger()
String	getLogPrefix()
IOrder	getOrder()
IVecInt	getOutLearnt()
RestartStrategy	getRestartStrategy()
<S extends ISolverService> SearchListener<S>	getSearchListener() Get the current SearchListener.
ISimplifier	getSimplifier()
Map<String,Number>	getStat() To obtain a map of the available statistics from the solver.
SolverStats	getStats()
int	getTimeout() Useful to check the internal timeout of the solver.
long	getTimeoutMs() Useful to check the internal timeout of the solver.
double[]	getVariableHeuristics() Read-Only access to the value of the heuristics for each variable.
ILits	getVocabulary()
protected void	initStats(SolverStats myStats)
boolean	isDBSimplificationAllowed() Indicate whether the solver is allowed to simplify the formula by propagating the truth value of top level satisfied variables.
protected boolean	isNeedToReduceDB()
boolean	isSatisfiable() Check the satisfiability of the set of constraints contained inside the solver.
boolean	isSatisfiable(boolean global) Check the satisfiability of the set of constraints contained inside the solver.
boolean	isSatisfiable(IVecInt assumps) Check the satisfiability of the set of constraints contained inside the solver.
boolean	isSatisfiable(IVecInt assumps, boolean global) Check the satisfiability of the set of constraints contained inside the solver.
boolean	isSolverKeptHot() Ask to the solver if it is in "hot" mode, meaning that the heuristics is not reset after call is isSatisfiable().
boolean	isVerbose() To know if the solver is in verbose mode (output allowed) or not.
void	learn(Constr c)
int[]	model() Si un mod?
boolean	model(int var) Provide the truth value of a specific variable in the model.
int[]	modelWithInternalVariables() That method is designed to be used to retrieve the real model of the current set of constraints, i.e. to provide the truth value of boolean variables used internally in the solver (for encoding purposes for instance).
protected int	nAssigns()
int	nConstraints() To know the number of constraints currently available in the solver.
int	newVar() Deprecated.
int	newVar(int howmany) Declare howmany variables in the problem (and thus in the vocabulary), that will be represented using the Dimacs format by integers ranging from 1 to howmany.
int	nextFreeVarId(boolean reserve) Ask the solver for a free variable identifier, in Dimacs format (i.e. a positive number).
int	nVars() Read-Only access to the number of variables declared in the solver.
int[]	primeImplicant() Provide a prime implicant, i.e. a set of literal that is sufficient to satisfy all constraints of the problem.
boolean	primeImplicant(int p) Check if a given literal is part of the prime implicant computed by the IProblem.primeImplicant() method.
void	printInfos(PrintWriter out, String prefix) To print additional informations regarding the problem.
void	printLearntClausesInfos(PrintWriter out, String prefix)
void	printStat(PrintStream out, String prefix) Display statistics to the given output stream Please use writers instead of stream.
void	printStat(PrintWriter out, String prefix) Display statistics to the given output writer
Constr	propagate()
int	realNumberOfVariables() Retrieve the real number of variables used in the solver.
protected void	reduceDB()
void	registerLiteral(int p) Tell the solver to consider that the literal is in the CNF.
boolean	removeConstr(IConstr co) Remove a constraint returned by one of the add method from the solver.
boolean	removeSubsumedConstr(IConstr co) Remove a constraint returned by one of the add method from the solver that is subsumed by a constraint already in the solver or to be added to the solver.
void	reset() Clean up the internal state of the solver.
void	setDataStructureFactory(D dsf) Change the internal representation of the constraints.
void	setDBSimplificationAllowed(boolean status) Set whether the solver is allowed to simplify the formula by propagating the truth value of top level satisfied variables.
void	setExpectedNumberOfClauses(int nb) To inform the solver of the expected number of clauses to read.
void	setKeepSolverHot(boolean keepHot) Changed the behavior of the SAT solver heuristics between successive calls.
void	setLearnedConstraintsDeletionStrategy(ConflictTimer timer, LearnedConstraintsEvaluationType evaluation)
void	setLearnedConstraintsDeletionStrategy(LearnedConstraintsDeletionStrategy lcds)
void	setLearnedConstraintsDeletionStrategy(LearnedConstraintsEvaluationType evaluation)
void	setLearner(LearningStrategy<D> learner)
void	setLogger(ICDCLLogger out)
void	setLogPrefix(String prefix) Set the prefix used to display information.
void	setNeedToReduceDB(boolean needToReduceDB)
void	setOrder(IOrder h)
void	setRestartStrategy(RestartStrategy restarter)
<S extends ISolverService> void	setSearchListener(SearchListener<S> sl) Allow the user to hook a listener to the solver to be notified of the main steps of the search process.
void	setSearchParams(SearchParams sp)
void	setSimplifier(ISimplifier simp) Setup the reason simplification strategy.
void	setSimplifier(SimplificationType simp) Setup the reason simplification strategy.
void	setTimeout(int t) To set the internal timeout of the solver.
void	setTimeoutMs(long t) To set the internal timeout of the solver.
void	setTimeoutOnConflicts(int count) To set the internal timeout of the solver.
void	setVerbose(boolean value) Set the verbosity of the solver
boolean	simplifyDB()
protected void	sortOnActivity()
void	stop() Ask the SAT solver to stop the search.
void	suggestNextLiteralToBranchOn(int l) Suggests to the SAT solver to branch next on the given literal.
String	toString()
String	toString(String prefix) Display a textual representation of the solver configuration.
Lbool	truthValue(int literal) To access the truth value of a specific literal under current assignment.
protected void	undoOne()
IVecInt	unsatExplanation() Retrieve an explanation of the inconsistency in terms of assumption literals.
void	unset(int p) Unset a unit clause.
void	varBumpActivity(int p) Update the activity of a variable v.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

out

protected ICDCLLogger out

constrs

protected final IVec<Constr> constrs

Set of original constraints.

learnts

protected final IVec<Constr> learnts

Set of learned constraints.

trail

protected final IVecInt trail

affectation en ordre chronologique

trailLim

protected final IVecInt trailLim

indice des s?parateurs des diff?rents niveau de d?cision dans trail

rootLevel

protected int rootLevel

S?pare les hypoth?ses incr?mentale et recherche

voc

protected ILits voc

undertimeout

protected volatile boolean undertimeout

dsfactory

protected D extends DataStructureFactory dsfactory

slistener

protected SearchListener slistener

NO_SIMPLIFICATION

public static final ISimplifier NO_SIMPLIFICATION

SIMPLE_SIMPLIFICATION

public final ISimplifier SIMPLE_SIMPLIFICATION

EXPENSIVE_SIMPLIFICATION

public final ISimplifier EXPENSIVE_SIMPLIFICATION

EXPENSIVE_SIMPLIFICATION_WLONLY

public final ISimplifier EXPENSIVE_SIMPLIFICATION_WLONLY

memory_based

public final LearnedConstraintsDeletionStrategy memory_based

Since:

2.1

glucose

public final LearnedConstraintsDeletionStrategy glucose

Since:

2.1

learnedConstraintsDeletionStrategy

protected LearnedConstraintsDeletionStrategy learnedConstraintsDeletionStrategy

Constructor Detail

Solver

public Solver(LearningStrategy<D> learner,
              D dsf,
              IOrder order,
              RestartStrategy restarter)

creates a Solver without LearningListener. A learningListener must be added to the solver, else it won't backtrack!!! A data structure factory must be provided, else it won't work either.

Solver

public Solver(LearningStrategy<D> learner,
              D dsf,
              SearchParams params,
              IOrder order,
              RestartStrategy restarter)

Solver

public Solver(LearningStrategy<D> learner,
              D dsf,
              SearchParams params,
              IOrder order,
              RestartStrategy restarter,
              ICDCLLogger logger)

Method Detail

dimacs2internal

protected IVecInt dimacs2internal(IVecInt in)

registerLiteral

public void registerLiteral(int p)

Description copied from interface: ISolver

Tell the solver to consider that the literal is in the CNF. Since model() only return the truth value of the literals that appear in the solver, it is sometimes required that the solver provides a default truth value for a given literal. This happens for instance for MaxSat.

Specified by:

registerLiteral in interface ISolver

Parameters:

p - the literal in Dimacs format that should appear in the model.

setDataStructureFactory

public final void setDataStructureFactory(D dsf)

Description copied from interface: ICDCL

Change the internal representation of the constraints. Note that the heuristics must be changed prior to calling that method.

Specified by:

setDataStructureFactory in interface ICDCL<D extends DataStructureFactory>

Parameters:

dsf - the internal factory

isVerbose

public boolean isVerbose()

Description copied from interface: ISolver

To know if the solver is in verbose mode (output allowed) or not.

Specified by:

isVerbose in interface ISolver

Returns:

true if the solver is verbose.

Since:

2.2

setVerbose

public void setVerbose(boolean value)

Description copied from interface: ISolver

Set the verbosity of the solver

Specified by:

setVerbose in interface ISolver

Parameters:

value -

Since:

2.2

setSearchListener

public <S extends ISolverService> void setSearchListener(SearchListener<S> sl)

Description copied from interface: ISolver

Allow the user to hook a listener to the solver to be notified of the main steps of the search process.

Specified by:

setSearchListener in interface ISolver

Parameters:

sl - a Search Listener.

getSearchListener

public <S extends ISolverService> SearchListener<S> getSearchListener()

Description copied from interface: ISolver

Get the current SearchListener.

Specified by:

getSearchListener in interface ISolver

Returns:

a Search Listener.

setLearner

public void setLearner(LearningStrategy<D> learner)

Specified by:

setLearner in interface ICDCL<D extends DataStructureFactory>

setTimeout

public void setTimeout(int t)

Description copied from interface: ISolver

To set the internal timeout of the solver. When the timeout is reached, a timeout exception is launched by the solver.

Specified by:

setTimeout in interface ISolver

Parameters:

t - the timeout (in s)

setTimeoutMs

public void setTimeoutMs(long t)

Description copied from interface: ISolver

To set the internal timeout of the solver. When the timeout is reached, a timeout exception is launched by the solver.

Specified by:

setTimeoutMs in interface ISolver

Parameters:

t - the timeout (in milliseconds)

setTimeoutOnConflicts

public void setTimeoutOnConflicts(int count)

Description copied from interface: ISolver

To set the internal timeout of the solver. When the timeout is reached, a timeout exception is launched by the solver. Here the timeout is given in number of conflicts. That way, the behavior of the solver should be the same across different architecture.

Specified by:

setTimeoutOnConflicts in interface ISolver

Parameters:

count - the timeout (in number of counflicts)

setSearchParams

public void setSearchParams(SearchParams sp)

Specified by:

setSearchParams in interface ICDCL<D extends DataStructureFactory>

setRestartStrategy

public void setRestartStrategy(RestartStrategy restarter)

Specified by:

setRestartStrategy in interface ICDCL<D extends DataStructureFactory>

getRestartStrategy

public RestartStrategy getRestartStrategy()

Specified by:

getRestartStrategy in interface ICDCL<D extends DataStructureFactory>

expireTimeout

public void expireTimeout()

Description copied from interface: ISolver

Expire the timeout of the solver.

Specified by:

expireTimeout in interface ISolver

nAssigns

protected int nAssigns()

nConstraints

public int nConstraints()

Description copied from interface: IProblem

To know the number of constraints currently available in the solver. (without taking into account learned constraints).

Specified by:

nConstraints in interface IProblem

Returns:

the number of constraints added to the solver

learn

public void learn(Constr c)

Specified by:

learn in interface Learner

decisionLevel

public final int decisionLevel()

newVar

@Deprecated
public int newVar()

Deprecated.

Description copied from interface: ISolver

Create a new variable in the solver (and thus in the vocabulary). WE STRONGLY ENCOURAGE TO PRECOMPUTE THE NUMBER OF VARIABLES NEEDED AND TO USE newVar(howmany) INSTEAD. IF YOU EXPERIENCE A PROBLEM OF EFFICIENCY WHEN READING/BUILDING YOUR SAT INSTANCE, PLEASE CHECK THAT YOU ARE NOT USING THAT METHOD.

Specified by:

newVar in interface ISolver

Returns:

the number of variables available in the vocabulary, which is the identifier of the new variable.

newVar

public int newVar(int howmany)

Description copied from interface: IProblem

Declare howmany variables in the problem (and thus in the vocabulary), that will be represented using the Dimacs format by integers ranging from 1 to howmany. That feature allows encodings to create additional variables with identifier starting at howmany+1.

Specified by:

newVar in interface IProblem

Parameters:

howmany - number of variables to create

Returns:

the total number of variables available in the solver (the highest variable number)

See Also:

IProblem.nVars()

addClause

public IConstr addClause(IVecInt literals)
                  throws ContradictionException

Description copied from interface: ISolver

Create a clause from a set of literals The literals are represented by non null integers such that opposite literals a represented by opposite values. (classical Dimacs way of representing literals).

Specified by:

addClause in interface ISolver

Parameters:

literals - a set of literals

Returns:

a reference to the constraint added in the solver, to use in removeConstr().

Throws:

ContradictionException - iff the vector of literals is empty or if it contains only falsified literals after unit propagation

See Also:

ISolver.removeConstr(IConstr)

removeConstr

public boolean removeConstr(IConstr co)

Description copied from interface: ISolver

Remove a constraint returned by one of the add method from the solver. All learned clauses will be cleared. Current implementation does not handle properly the case of unit clauses.

Specified by:

removeConstr in interface ISolver

Parameters:

co - a constraint returned by one of the add method.

Returns:

true if the constraint was successfully removed.

removeSubsumedConstr

public boolean removeSubsumedConstr(IConstr co)

Description copied from interface: ISolver

Remove a constraint returned by one of the add method from the solver that is subsumed by a constraint already in the solver or to be added to the solver. Unlike the removeConstr() method, learned clauses will NOT be cleared. That method is expected to be used to remove constraints used in the optimization process. In order to prevent a wrong from the user, the method will only work if the argument is the last constraint added to the solver. An illegal argument exception will be thrown in other cases.

Specified by:

removeSubsumedConstr in interface ISolver

Parameters:

co - a constraint returned by one of the add method. It must be the latest constr added to the solver.

Returns:

true if the constraint was successfully removed.

Since:

2.1

addAllClauses

public void addAllClauses(IVec<IVecInt> clauses)
                   throws ContradictionException

Description copied from interface: ISolver

Create clauses from a set of set of literals. This is convenient to create in a single call all the clauses (mandatory for the distributed version of the solver). It is mainly a loop to addClause().

Specified by:

addAllClauses in interface ISolver

Parameters:

clauses - a vector of set (VecInt) of literals in the dimacs format. The vector can be reused since the solver is not supposed to keep a reference to that vector.

Throws:

ContradictionException - iff the vector of literals is empty or if it contains only falsified literals after unit propagation

See Also:

ISolver.addClause(IVecInt)

addAtMost

public IConstr addAtMost(IVecInt literals,
                         int degree)
                  throws ContradictionException

Description copied from interface: ISolver

Create a cardinality constraint of the type "at most n of those literals must be satisfied"

Specified by:

addAtMost in interface ISolver

Parameters:

literals - a set of literals The vector can be reused since the solver is not supposed to keep a reference to that vector.

degree - the degree (n) of the cardinality constraint

Returns:

a reference to the constraint added in the solver, to use in removeConstr().

Throws:

ContradictionException - iff the vector of literals is empty or if it contains more than degree satisfied literals after unit propagation

See Also:

ISolver.removeConstr(IConstr)

addAtLeast

public IConstr addAtLeast(IVecInt literals,
                          int degree)
                   throws ContradictionException

Description copied from interface: ISolver

Create a cardinality constraint of the type "at least n of those literals must be satisfied"

Specified by:

addAtLeast in interface ISolver

Parameters:

literals - a set of literals. The vector can be reused since the solver is not supposed to keep a reference to that vector.

degree - the degree (n) of the cardinality constraint

Returns:

a reference to the constraint added in the solver, to use in removeConstr().

Throws:

ContradictionException - iff the vector of literals is empty or if degree literals are not remaining unfalsified after unit propagation

See Also:

ISolver.removeConstr(IConstr)

addExactly

public IConstr addExactly(IVecInt literals,
                          int n)
                   throws ContradictionException

Description copied from interface: ISolver

Create a cardinality constraint of the type "exactly n of those literals must be satisfied".

Specified by:

addExactly in interface ISolver

Parameters:

literals - a set of literals. The vector can be reused since the solver is not supposed to keep a reference to that vector.

n - the number of literals that must be satisfied

Returns:

a reference to the constraint added to the solver. It might return an object representing a group of constraints.

Throws:

ContradictionException - iff the constraint is trivially unsatisfiable.

simplifyDB

public boolean simplifyDB()

model

public int[] model()

Si un mod?le est trouv?, ce vecteur contient le mod?le.

Specified by:

model in interface IProblem

Returns:

un mod?le de la formule.

See Also:

IProblem.isSatisfiable(), IProblem.isSatisfiable(IVecInt)

enqueue

public boolean enqueue(int p)

Description copied from interface: UnitPropagationListener

satisfies a literal

Specified by:

enqueue in interface UnitPropagationListener

Parameters:

p - a literal

Returns:

true if the assignment looks possible, false if a conflict occurs.

enqueue

public boolean enqueue(int p,
                       Constr from)

Description copied from interface: UnitPropagationListener

satisfies a literal

Specified by:

enqueue in interface UnitPropagationListener

Parameters:

p - a literal

from - a reason explaining why p should be satisfied.

Returns:

true if the assignment looks possible, false if a conflict occurs.

analyze

public void analyze(Constr confl,
                    Pair results)
             throws TimeoutException

Throws:

TimeoutException - if the timeout is reached during conflict analysis.

analyzeFinalConflictInTermsOfAssumptions

public IVecInt analyzeFinalConflictInTermsOfAssumptions(Constr confl,
                                                        IVecInt assumps,
                                                        int conflictingLiteral)

Derive a subset of the assumptions causing the inconistency.

Parameters:

confl - the last conflict of the search, occuring at root level.

assumps - the set of assumption literals

conflictingLiteral - the literal detected conflicting while propagating assumptions.

Returns:

a subset of assumps causing the inconsistency.

Since:

2.2

setSimplifier

public void setSimplifier(SimplificationType simp)

Description copied from interface: ICDCL

Setup the reason simplification strategy. By default, there is no reason simplification. NOTE THAT REASON SIMPLIFICATION DOES NOT WORK WITH SPECIFIC DATA STRUCTURE FOR HANDLING BOTH BINARY AND TERNARY CLAUSES.

Specified by:

setSimplifier in interface ICDCL<D extends DataStructureFactory>

Parameters:

simp - a simplification type.

setSimplifier

public void setSimplifier(ISimplifier simp)

Description copied from interface: ICDCL

Setup the reason simplification strategy. By default, there is no reason simplification. NOTE THAT REASON SIMPLIFICATION IS ONLY ALLOWED FOR WL CLAUSAL data structures. USING REASON SIMPLIFICATION ON CB CLAUSES, CARDINALITY CONSTRAINTS OR PB CONSTRAINTS MIGHT RESULT IN INCORRECT RESULTS.

Specified by:

setSimplifier in interface ICDCL<D extends DataStructureFactory>

getSimplifier

public ISimplifier getSimplifier()

Specified by:

getSimplifier in interface ICDCL<D extends DataStructureFactory>

undoOne

protected void undoOne()

claBumpActivity

public void claBumpActivity(Constr confl)

Propagate activity to a constraint

Parameters:

confl - a constraint

varBumpActivity

public void varBumpActivity(int p)

Description copied from interface: VarActivityListener

Update the activity of a variable v.

Parameters:

p - a literal (v<<1 or v<<1^1)

propagate

public Constr propagate()

Returns:

null if not conflict is found, else a conflicting constraint.

assume

public boolean assume(int p)

Returns:

false ssi conflit imm?diat.

cancelUntil

protected void cancelUntil(int level)

Cancel several levels of assumptions

Parameters:

level -

analyzeAtRootLevel

protected void analyzeAtRootLevel(Constr conflict)

primeImplicant

public int[] primeImplicant()

Description copied from interface: IProblem

Provide a prime implicant, i.e. a set of literal that is sufficient to satisfy all constraints of the problem.

Specified by:

primeImplicant in interface IProblem

Returns:

a prime implicant of the formula as an array of literal, Dimacs format.

primeImplicant

public boolean primeImplicant(int p)

Description copied from interface: IProblem

Check if a given literal is part of the prime implicant computed by the IProblem.primeImplicant() method.

Specified by:

primeImplicant in interface IProblem

Parameters:

p - a literal in Dimacs format

Returns:

true iff p belongs to IProblem.primeImplicant()

model

public boolean model(int var)

Description copied from interface: IProblem

Provide the truth value of a specific variable in the model. That method should be called AFTER isSatisfiable() if the formula is satisfiable. Else an exception UnsupportedOperationException is launched.

Specified by:

model in interface IProblem

Parameters:

var - the variable id in Dimacs format

Returns:

the truth value of that variable in the model

See Also:

IProblem.model()

clearLearntClauses

public void clearLearntClauses()

Description copied from interface: ISolver

Remove clauses learned during the solving process.

Specified by:

clearLearntClauses in interface ISolver

reduceDB

protected void reduceDB()

sortOnActivity

protected void sortOnActivity()

Parameters:

learnts -

decayActivities

protected void decayActivities()

isSatisfiable

public boolean isSatisfiable()
                      throws TimeoutException

Description copied from interface: IProblem

Check the satisfiability of the set of constraints contained inside the solver.

Specified by:

isSatisfiable in interface IProblem

Returns:

true iff the set of constraints is satisfiable, else false.

Throws:

TimeoutException

isSatisfiable

public boolean isSatisfiable(boolean global)
                      throws TimeoutException

Description copied from interface: IProblem

Check the satisfiability of the set of constraints contained inside the solver.

Specified by:

isSatisfiable in interface IProblem

Parameters:

global - whether that call is part of a global process (i.e. optimization) or not. if (global), the timeout will not be reset between each call.

Returns:

true iff the set of constraints is satisfiable, else false.

Throws:

TimeoutException

isSatisfiable

public boolean isSatisfiable(IVecInt assumps)
                      throws TimeoutException

Description copied from interface: IProblem

Check the satisfiability of the set of constraints contained inside the solver.

Specified by:

isSatisfiable in interface IProblem

Parameters:

assumps - a set of literals (represented by usual non null integers in Dimacs format).

Returns:

true if the set of constraints is satisfiable when literals are satisfied, else false.

Throws:

TimeoutException

fixedSize

public final LearnedConstraintsDeletionStrategy fixedSize(int maxsize)

setLearnedConstraintsDeletionStrategy

public void setLearnedConstraintsDeletionStrategy(LearnedConstraintsDeletionStrategy lcds)

Specified by:

setLearnedConstraintsDeletionStrategy in interface ICDCL<D extends DataStructureFactory>

isSatisfiable

public boolean isSatisfiable(IVecInt assumps,
                             boolean global)
                      throws TimeoutException

Description copied from interface: IProblem

Check the satisfiability of the set of constraints contained inside the solver.

Specified by:

isSatisfiable in interface IProblem

Parameters:

assumps - a set of literals (represented by usual non null integers in Dimacs format).

global - whether that call is part of a global process (i.e. optimization) or not. if (global), the timeout will not be reset between each call.

Returns:

true if the set of constraints is satisfiable when literals are satisfied, else false.

Throws:

TimeoutException

printInfos

public void printInfos(PrintWriter out,
                       String prefix)

Description copied from interface: IProblem

To print additional informations regarding the problem.

Specified by:

printInfos in interface IProblem

Parameters:

out - the place to print the information

prefix - the prefix to put in front of each line

printLearntClausesInfos

public void printLearntClausesInfos(PrintWriter out,
                                    String prefix)

Since:

2.1

getStats

public SolverStats getStats()

initStats

protected void initStats(SolverStats myStats)

Parameters:

myStats -

Since:

2.2

getOrder

public IOrder getOrder()

Specified by:

getOrder in interface ICDCL<D extends DataStructureFactory>

setOrder

public void setOrder(IOrder h)

Specified by:

setOrder in interface ICDCL<D extends DataStructureFactory>

getVocabulary

public ILits getVocabulary()

reset

public void reset()

Description copied from interface: ISolver

Clean up the internal state of the solver.

Specified by:

reset in interface ISolver

nVars

public int nVars()

Description copied from interface: ISolverService

Read-Only access to the number of variables declared in the solver.

Specified by:

nVars in interface IProblem

Specified by:

nVars in interface ISolverService

Returns:

the maximum variable id (Dimacs format) reserved in the solver.

See Also:

IProblem.newVar(int)

addConstr

protected IConstr addConstr(Constr constr)

Parameters:

constr - a constraint implementing the Constr interface.

Returns:

a reference to the constraint for external use.

getDSFactory

public DataStructureFactory getDSFactory()

getOutLearnt

public IVecInt getOutLearnt()

getIthConstr

public IConstr getIthConstr(int i)

returns the ith constraint in the solver.

Parameters:

i - the constraint number (begins at 0)

Returns:

the ith constraint

printStat

public void printStat(PrintStream out,
                      String prefix)

Description copied from interface: ISolver

Display statistics to the given output stream Please use writers instead of stream.

Specified by:

printStat in interface ISolver

prefix - the prefix to put in front of each line

See Also:

ISolver.printStat(PrintWriter, String)

printStat

public void printStat(PrintWriter out,
                      String prefix)

Description copied from interface: ISolver

Display statistics to the given output writer

Specified by:

printStat in interface ISolver

prefix - the prefix to put in front of each line

toString

public String toString(String prefix)

Description copied from interface: ISolver

Display a textual representation of the solver configuration.

Specified by:

toString in interface ISolver

Parameters:

prefix - the prefix to use on each line.

Returns:

a textual description of the solver internals.

toString

public String toString()

Overrides:

toString in class Object

getTimeout

public int getTimeout()

Description copied from interface: ISolver

Useful to check the internal timeout of the solver.

Specified by:

getTimeout in interface ISolver

Returns:

the internal timeout of the solver (in seconds)

getTimeoutMs

public long getTimeoutMs()

Description copied from interface: ISolver

Useful to check the internal timeout of the solver.

Specified by:

getTimeoutMs in interface ISolver

Returns:

the internal timeout of the solver (in milliseconds)

Since:

2.1

setExpectedNumberOfClauses

public void setExpectedNumberOfClauses(int nb)

Description copied from interface: ISolver

To inform the solver of the expected number of clauses to read. This is an optional method, that is called when the p cnf line is read in dimacs formatted input file. Note that this method is supposed to be called AFTER a call to newVar(int)

Specified by:

setExpectedNumberOfClauses in interface ISolver

Parameters:

nb - the expected number of clauses.

See Also:

IProblem.newVar(int)

getStat

public Map<String,Number> getStat()

Description copied from interface: ISolver

To obtain a map of the available statistics from the solver. Note that some keys might be specific to some solvers.

Specified by:

getStat in interface ISolver

Returns:

a Map with the name of the statistics as key.

findModel

public int[] findModel()
                throws TimeoutException

Description copied from interface: IProblem

Look for a model satisfying all the clauses available in the problem. It is an alternative to isSatisfiable() and model() methods, as shown in the pseudo-code: if (isSatisfiable()) { return model(); } return null;

Specified by:

findModel in interface IProblem

Returns:

a model of the formula as an array of literals to satisfy, or null if no model is found

Throws:

TimeoutException - if a model cannot be found within the given timeout.

findModel

public int[] findModel(IVecInt assumps)
                throws TimeoutException

Description copied from interface: IProblem

Look for a model satisfying all the clauses available in the problem. It is an alternative to isSatisfiable(IVecInt) and model() methods, as shown in the pseudo-code: if (isSatisfiable(assumpt)) { return model(); } return null;

Specified by:

findModel in interface IProblem

Returns:

a model of the formula as an array of literals to satisfy, or null if no model is found

Throws:

TimeoutException - if a model cannot be found within the given timeout.

isDBSimplificationAllowed

public boolean isDBSimplificationAllowed()

Description copied from interface: ISolver

Indicate whether the solver is allowed to simplify the formula by propagating the truth value of top level satisfied variables. Note that the solver should not be allowed to perform such simplification when constraint removal is planned.

Specified by:

isDBSimplificationAllowed in interface ISolver

setDBSimplificationAllowed

public void setDBSimplificationAllowed(boolean status)

Description copied from interface: ISolver

Set whether the solver is allowed to simplify the formula by propagating the truth value of top level satisfied variables. Note that the solver should not be allowed to perform such simplification when constraint removal is planned.

Specified by:

setDBSimplificationAllowed in interface ISolver

nextFreeVarId

public int nextFreeVarId(boolean reserve)

Description copied from interface: ISolver

Ask the solver for a free variable identifier, in Dimacs format (i.e. a positive number). Note that a previous call to newVar(max) will reserve in the solver the variable identifier from 1 to max, so nextFreeVarId() would return max+1, even if some variable identifiers smaller than max are not used. By default, the method will always answer by the maximum variable identifier used so far + 1. The number of variables reserved in the solver is accessible through the ISolver.realNumberOfVariables() method.

Specified by:

nextFreeVarId in interface ISolver

Parameters:

reserve - if true, the maxVarId is updated in the solver, i.e. successive calls to nextFreeVarId(true) will return increasing variable id while successive calls to nextFreeVarId(false) will always answer the same.

Returns:

a variable identifier not in use in the constraints already inside the solver.

Since:

2.1

See Also:

ISolver.realNumberOfVariables()

addBlockingClause

public IConstr addBlockingClause(IVecInt literals)
                          throws ContradictionException

Description copied from interface: ISolver

Add a clause in order to prevent an assignment to occur. This happens usually when iterating over models for instance.

Specified by:

addBlockingClause in interface ISolver

Returns:

Throws:

ContradictionException

Since:

2.1

unset

public void unset(int p)

Description copied from interface: UnitPropagationListener

Unset a unit clause. The effect of such method is to unset all truth values on the stack until the given literal is found (that literal included).

Specified by:

unset in interface UnitPropagationListener

Since:

2.1

setLogPrefix

public void setLogPrefix(String prefix)

Description copied from interface: ISolver

Set the prefix used to display information.

Specified by:

setLogPrefix in interface ISolver

Parameters:

prefix - the prefix to be in front of each line of text

Since:

2.2

getLogPrefix

public String getLogPrefix()

Specified by:

getLogPrefix in interface ISolver

Returns:

the string used to prefix the output.

Since:

2.2

unsatExplanation

public IVecInt unsatExplanation()

Description copied from interface: ISolver

Retrieve an explanation of the inconsistency in terms of assumption literals. This is only application when isSatisfiable(assumps) is used. Note that !isSatisfiable(assumps)&&assumps.contains(unsatExplanation()) should hold.

Specified by:

unsatExplanation in interface ISolver

Returns:

a subset of the assumptions used when calling isSatisfiable(assumps). Will return null if not applicable (i.e. no assumptions used).

Since:

2.2

See Also:

IProblem.isSatisfiable(IVecInt), IProblem.isSatisfiable(IVecInt, boolean)

modelWithInternalVariables

public int[] modelWithInternalVariables()

Description copied from interface: ISolver

That method is designed to be used to retrieve the real model of the current set of constraints, i.e. to provide the truth value of boolean variables used internally in the solver (for encoding purposes for instance). If no variables are added in the solver, then Arrays.equals(model(),modelWithInternalVariables()). In case new variables are added to the solver, then the number of models returned by that method is greater of equal to the number of models returned by model() when using a ModelIterator.

Specified by:

modelWithInternalVariables in interface ISolver

Returns:

an array of literals, in Dimacs format, corresponding to a model of the formula over all the variables declared in the solver.

Since:

2.3.1

See Also:

IProblem.model(), ModelIterator

realNumberOfVariables

public int realNumberOfVariables()

Description copied from interface: ISolver

Retrieve the real number of variables used in the solver. In many cases, realNumberOfVariables()==nVars(). However, when working with SAT encodings or translation from MAXSAT to PMS, one can have realNumberOfVariables()>nVars(). Those additional variables are supposed to be created using the ISolver.nextFreeVarId(boolean) method.

Specified by:

realNumberOfVariables in interface ISolver

Returns:

the number of variables reserved in the solver.

Since:

2.3.1

See Also:

ISolver.nextFreeVarId(boolean)

stop

public void stop()

Description copied from interface: ISolverService

Ask the SAT solver to stop the search.

Specified by:

stop in interface ISolverService

Since:

2.3.2

backtrack

public void backtrack(int[] reason)

Description copied from interface: ISolverService

Ask the SAT solver to backtrack. It is mandatory to provide a reason for backtracking, in terms of literals (which should be falsified under current assignment). The reason is not added to the clauses of the solver: only the result of the analysis is stored in the learned clauses. Note that these clauses may be removed latter.

Specified by:

backtrack in interface ISolverService

Parameters:

reason - a set of literals, in Dimacs format, currently falsified, i.e. for (int l : reason) assert truthValue(l) == Lbool.FALSE

Since:

2.3.2

truthValue

public Lbool truthValue(int literal)

Description copied from interface: ISolverService

To access the truth value of a specific literal under current assignment.

Specified by:

truthValue in interface ISolverService

Parameters:

literal - a Dimacs literal, i.e. a non-zero integer.

Returns:

true or false if the literal is assigned, else undefined.

Since:

2.3.2

currentDecisionLevel

public int currentDecisionLevel()

Description copied from interface: ISolverService

To access the current decision level

Specified by:

currentDecisionLevel in interface ISolverService

Since:

2.3.2

getLiteralsPropagatedAt

public int[] getLiteralsPropagatedAt(int decisionLevel)

Description copied from interface: ISolverService

To access the literals propagated at a specific decision level.

Specified by:

getLiteralsPropagatedAt in interface ISolverService

Parameters:

decisionLevel - a decision level between 0 and #currentDecisionLevel()

Since:

2.3.2

suggestNextLiteralToBranchOn

public void suggestNextLiteralToBranchOn(int l)

Description copied from interface: ISolverService

Suggests to the SAT solver to branch next on the given literal.

Specified by:

suggestNextLiteralToBranchOn in interface ISolverService

Parameters:

l - a literal in Dimacs format.

Since:

2.3.2

isNeedToReduceDB

protected boolean isNeedToReduceDB()

setNeedToReduceDB

public void setNeedToReduceDB(boolean needToReduceDB)

Specified by:

setNeedToReduceDB in interface ICDCL<D extends DataStructureFactory>

setLogger

public void setLogger(ICDCLLogger out)

Specified by:

setLogger in interface ICDCL<D extends DataStructureFactory>

getLogger

public ICDCLLogger getLogger()

Specified by:

getLogger in interface ICDCL<D extends DataStructureFactory>

getVariableHeuristics

public double[] getVariableHeuristics()

Description copied from interface: ISolverService

Read-Only access to the value of the heuristics for each variable. Note that for efficiency reason, the real array storing the value of the heuristics is returned. DO NOT CHANGE THE VALUES IN THAT ARRAY.

Specified by:

getVariableHeuristics in interface ISolverService

Returns:

the value of the heuristics for each variable (using Dimacs index).

getLearnedConstraints

public IVec<Constr> getLearnedConstraints()

Description copied from interface: ISolverService

Read-Only access to the list of constraints learned and not deleted so far in the solver. Note that for efficiency reason, the real list of constraints managed by the solver is returned. DO NOT MODIFY THAT LIST NOR ITS CONSTRAINTS.

Specified by:

getLearnedConstraints in interface ISolverService

Returns:

the constraints learned and kept so far by the solver.

setLearnedConstraintsDeletionStrategy

public void setLearnedConstraintsDeletionStrategy(ConflictTimer timer,
                                                  LearnedConstraintsEvaluationType evaluation)

Specified by:

setLearnedConstraintsDeletionStrategy in interface ICDCL<D extends DataStructureFactory>

Parameters:

timer - when to apply constraints cleanup.

evaluation - the strategy used to evaluate learned clauses.

Since:

2.3.2

setLearnedConstraintsDeletionStrategy

public void setLearnedConstraintsDeletionStrategy(LearnedConstraintsEvaluationType evaluation)

Specified by:

setLearnedConstraintsDeletionStrategy in interface ICDCL<D extends DataStructureFactory>

Parameters:

evaluation - the strategy used to evaluate learned clauses.

Since:

2.3.2

isSolverKeptHot

public boolean isSolverKeptHot()

Description copied from interface: ISolver

Ask to the solver if it is in "hot" mode, meaning that the heuristics is not reset after call is isSatisfiable(). This is only useful in case of repeated calls to the solver with same set of variables.

Specified by:

isSolverKeptHot in interface ISolver

Returns:

true iff the solver keep the heuristics value unchanged across calls.

setKeepSolverHot

public void setKeepSolverHot(boolean keepHot)

Description copied from interface: ISolver

Changed the behavior of the SAT solver heuristics between successive calls. If the value is true, then the solver will be "hot" on reuse, i.e. the heuristics will not be reset. Else the heuristics will be reset.

Specified by:

setKeepSolverHot in interface ISolver

Parameters:

keepHot - true to keep the heuristics values across calls, false either.

addClause

public void addClause(int[] literals)

Description copied from interface: ISolverService

Add a new clause in the SAT solver. The new clause may contain new variables. The clause may be falsified, in that case, the difference with backtrack() is that the new clause is appended to the solver as a regular clause. Thus it will not be removed by aggressive clause deletion. The clause may be assertive at a given decision level. In that case, the solver should backtrack to the proper decision level. In other cases, the search should simply proceed.

Specified by:

addClause in interface ISolverService

Parameters:

literals - a set of literals in Dimacs format.