org.sat4j.tools
Class DimacsStringSolver

java.lang.Object
  org.sat4j.tools.DimacsStringSolver

All Implemented Interfaces:

Serializable, IProblem, ISolver

public class DimacsStringSolver
extends Object
implements ISolver

Solver used to write down a CNF into a String. It is especially useful compared to the DimacsOutputSolver because the number of clauses does not need to be known in advance.

Author:

leberre

See Also:

Serialized Form

Constructor Summary

DimacsStringSolver()

DimacsStringSolver(int initSize)

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.
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.
void	clearLearntClauses() Remove clauses learned during the solving process.
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.
String	getLogPrefix()
StringBuffer	getOut()
SearchListener	getSearchListener() Get the current SearchListener.
Map<String,Number>	getStat() To obtain a map of the available statistics from the solver.
int	getTimeout() Useful to check the internal timeout of the solver.
long	getTimeoutMs() Useful to check the internal timeout of the solver.
boolean	isDBSimplificationAllowed() Indicate whether the solver is allowed to simplify the formula by propagating the truth value of top level satisfied variables.
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	isVerbose() To know if the solver is in verbose mode (output allowed) or not.
int[]	model() Provide a model (if any) for a satisfiable formula.
boolean	model(int var) Provide the truth value of a specific variable in the model.
int	nConstraints() To know the number of constraints currently available in the solver.
int	newVar() Create a new variable in the solver (and thus in the vocabulary).
int	newVar(int howmany) Create howmany variables in the solver (and thus in the vocabulary).
int	nextFreeVarId(boolean reserve) Ask the solver for a free variable identifier, in Dimacs format (i.e. a positive number).
int	nVars() To know the number of variables used in the solver.
void	printInfos(PrintWriter output, String prefix) To print additional informations regarding the problem.
void	printStat(PrintStream output, String prefix) Display statistics to the given output stream Please use writers instead of stream.
void	printStat(PrintWriter output, String prefix) Display statistics to the given output writer
boolean	removeConstr(IConstr c) Remove a constraint returned by one of the add method from the solver.
boolean	removeSubsumedConstr(IConstr c) 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	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	setLogPrefix(String prefix) Set the prefix used to display information.
protected void	setNbVars(int howmany)
void	setSearchListener(SearchListener sl) Allow the user to hook a listener to the solver to be notified of the main steps of the search process.
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
String	toString()
String	toString(String prefix) Display a textual representation of the solver configuration.
IVecInt	unsatExplanation() Retrieve an explanation of the inconsistency in terms of assumption literals.

Methods inherited from class java.lang.Object

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

Constructor Detail

DimacsStringSolver

public DimacsStringSolver()

DimacsStringSolver

public DimacsStringSolver(int initSize)

Method Detail

getOut

public StringBuffer getOut()

newVar

public int newVar()

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: ISolver

Create howmany variables in the solver (and thus in the vocabulary).

Specified by:

newVar in interface ISolver

Parameters:

howmany - number of variables to create

Returns:

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

setNbVars

protected void setNbVars(int howmany)

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:

ISolver.newVar(int)

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 c)

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:

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

Returns:

true if the constraint was successfully removed.

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 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 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)

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)

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

reset

public void reset()

Description copied from interface: ISolver

Clean up the internal state of the solver.

Specified by:

reset in interface ISolver

printStat

public void printStat(PrintStream output,
                      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 output,
                      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

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.

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.

clearLearntClauses

public void clearLearntClauses()

Description copied from interface: ISolver

Remove clauses learned during the solving process.

Specified by:

clearLearntClauses in interface ISolver

model

public int[] model()

Description copied from interface: IProblem

Provide a model (if any) for a satisfiable formula. That method should be called AFTER isSatisfiable() or isSatisfiable(IVecInt) if the formula is satisfiable. Else an exception UnsupportedOperationException is launched.

Specified by:

model in interface IProblem

Returns:

a model of the formula as an array of literals to satisfy.

See Also:

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

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()

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 if 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

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.

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

nVars

public int nVars()

Description copied from interface: IProblem

To know the number of variables used in the solver.

Specified by:

nVars in interface IProblem

Returns:

the number of variables created using newVar().

toString

public String toString()

Overrides:

toString in class Object

expireTimeout

public void expireTimeout()

Description copied from interface: ISolver

Expire the timeout of the solver.

Specified by:

expireTimeout in interface ISolver

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

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 if the set of constraints is satisfiable, else false.

Throws:

TimeoutException

printInfos

public void printInfos(PrintWriter output,
                       String prefix)

Description copied from interface: IProblem

To print additional informations regarding the problem.

Specified by:

printInfos in interface IProblem

Parameters:

output - the place to print the information

prefix - the prefix to put in front of each line

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)

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

setSearchListener

public void setSearchListener(SearchListener 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.

Since:

2.1

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.

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

removeSubsumedConstr

public boolean removeSubsumedConstr(IConstr c)

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:

c - 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

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

getSearchListener

public SearchListener getSearchListener()

Description copied from interface: ISolver

Get the current SearchListener.

Specified by:

getSearchListener in interface ISolver

Returns:

a Search Listener.

Since:

2.2

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 - true to allow the solver to output messages on the console, false either.

Since:

2.2

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)