org.sat4j.minisat.constraints.cnf

Class UnitClause

java.lang.Object

org.sat4j.minisat.constraints.cnf.UnitClause

All Implemented Interfaces:

Constr, IConstr

public class UnitClause
extends Object
implements Constr

Since:

2.1

Author:

daniel

Field Summary

Fields

Modifier and Type	Field and Description
protected double	activity
protected int	literal

Constructor Summary

Constructors

Constructor and Description
UnitClause(int value)

Method Summary

Methods

Modifier and Type	Method and Description
void	assertConstraint(UnitPropagationListener s) Method called when the constraint is to be asserted.
void	assertConstraintIfNeeded(UnitPropagationListener s) Method called when the constraint is added to the solver "on the fly".
void	calcReason(int p, IVecInt outReason) Compute the reason for a given assignment.
void	calcReasonOnTheFly(int p, IVecInt trail, IVecInt outReason) Compute the reason for a given assignment in a the constraint created on the fly in the solver.
boolean	canBePropagatedMultipleTimes() Partition constraints into the ones that can only be found once on the trail (e.g. clauses) and the ones that can be found several times (e.g.
void	forwardActivity(double claInc)
int	get(int i) returns the ith literal in the constraint
double	getActivity() To obtain the activity of the constraint.
void	incActivity(double claInc) Increase the constraint activity.
boolean	learnt()
boolean	locked() Indicate wether a constraint is responsible from an assignment.
boolean	propagate(UnitPropagationListener s, int p)
void	register() Register the constraint to the solver.
void	remove(UnitPropagationListener upl) Remove a constraint from the solver.
void	rescaleBy(double d) Rescale the clause activity by a value.
void	setActivity(double claInc) Set the activity at a specific value
void	setLearnt() Mark a constraint as learnt.
boolean	simplify() Simplifies a constraint, by removing top level falsified literals for instance.
int	size()
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

literal

protected final int literal

activity

protected double activity

Constructor Detail

UnitClause

public UnitClause(int value)

Method Detail

assertConstraint

public void assertConstraint(UnitPropagationListener s)

Description copied from interface: Constr

Method called when the constraint is to be asserted. It means that the constraint was learned during the search and it should now propagate some truth values. In the clausal case, only one literal should be propagated. In other cases, it might be different.

Specified by:

assertConstraint in interface Constr

Parameters:

s - a UnitPropagationListener to use for unit propagation.

assertConstraintIfNeeded

public void assertConstraintIfNeeded(UnitPropagationListener s)

Description copied from interface: Constr

Method called when the constraint is added to the solver "on the fly". In that case, the constraint may or may not have to propagate some literals, unlike the Constr.assertConstraint(UnitPropagationListener) method.

Specified by:

assertConstraintIfNeeded in interface Constr

Parameters:

s - a UnitPropagationListener to use for unit propagation.

calcReason

public void calcReason(int p,
              IVecInt outReason)

Description copied from interface: Constr

Compute the reason for a given assignment. If the constraint is a clause, it is supposed to be either a unit clause or a falsified one. It is expected that the falsification of the constraint has been detected as soon at is occurs (e.g. using Propagatable.propagate(UnitPropagationListener, int).

Specified by:

calcReason in interface Constr

Parameters:

p - a satisfied literal (or Lit.UNDEFINED)

outReason - the list of falsified literals whose negation is the reason of the assignment of p to true.

getActivity

public double getActivity()

Description copied from interface: IConstr

To obtain the activity of the constraint.

Specified by:

getActivity in interface IConstr

Returns:

the activity of the clause.

incActivity

public void incActivity(double claInc)

Description copied from interface: Constr

Increase the constraint activity.

Specified by:

incActivity in interface Constr

Parameters:

claInc - the value to increase the activity with

setActivity

public void setActivity(double claInc)

Description copied from interface: Constr

Set the activity at a specific value

Specified by:

setActivity in interface Constr

Parameters:

claInc - the new activity

locked

public boolean locked()

Description copied from interface: Constr

Indicate wether a constraint is responsible from an assignment.

Specified by:

locked in interface Constr

Returns:

true if a constraint is a "reason" for an assignment.

register

public void register()

Description copied from interface: Constr

Register the constraint to the solver.

Specified by:

register in interface Constr

remove

public void remove(UnitPropagationListener upl)

Description copied from interface: Constr

Remove a constraint from the solver.

Specified by:

remove in interface Constr

rescaleBy

public void rescaleBy(double d)

Description copied from interface: Constr

Rescale the clause activity by a value.

Specified by:

rescaleBy in interface Constr

Parameters:

d - the value to rescale the clause activity with.

setLearnt

public void setLearnt()

Description copied from interface: Constr

Mark a constraint as learnt.

Specified by:

setLearnt in interface Constr

simplify

public boolean simplify()

Description copied from interface: Constr

Simplifies a constraint, by removing top level falsified literals for instance.

Specified by:

simplify in interface Constr

Returns:

true iff the constraint is satisfied and can be removed from the database.

propagate

public boolean propagate(UnitPropagationListener s,
                int p)

get

public int get(int i)

Description copied from interface: IConstr

returns the ith literal in the constraint

Specified by:

get in interface IConstr

Parameters:

i - the index of the literal

Returns:

a literal

learnt

public boolean learnt()

Specified by:

learnt in interface IConstr

Returns:

true iff the clause was learnt during the search

size

public int size()

Specified by:

size in interface IConstr

Returns:

the number of literals in the constraint.

forwardActivity

public void forwardActivity(double claInc)

Specified by:

forwardActivity in interface Constr

toString

public String toString()

Overrides:

toString in class Object

canBePropagatedMultipleTimes

public boolean canBePropagatedMultipleTimes()

Description copied from interface: IConstr

Partition constraints into the ones that can only be found once on the trail (e.g. clauses) and the ones that can be found several times (e.g. cardinality constraints and pseudo-boolean constraints).

Specified by:

canBePropagatedMultipleTimes in interface IConstr

Returns:

true if the constraint can be used several times as a reason to propagate a literal.

calcReasonOnTheFly

public void calcReasonOnTheFly(int p,
                      IVecInt trail,
                      IVecInt outReason)

Description copied from interface: Constr

Compute the reason for a given assignment in a the constraint created on the fly in the solver. Compared to the method Constr.calcReason(int, IVecInt), the falsification may not have been detected as soon as possible. As such, it is necessary to take into account the order of the literals in the trail.

Specified by:

calcReasonOnTheFly in interface Constr

Parameters:

p - a satisfied literal (or Lit.UNDEFINED)

trail - all the literals satisfied in the solvers, should not be modified.

outReason - a list of falsified literals whose negation is the reason of the assignment of p to true.