org.sat4j.minisat.constraints.card

Class AtLeast

java.lang.Object

org.sat4j.minisat.constraints.card.AtLeast

All Implemented Interfaces:

Serializable, Constr, Propagatable, Undoable, IConstr

public class AtLeast
extends Object
implements Propagatable, Constr, Undoable, Serializable

Author:

leberre Contrainte de cardinalit?

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected int[]	lits constraint literals
protected int	maxUnsatisfied number of allowed falsified literal
protected ILits	voc

Constructor Summary

Constructors

Constructor and Description
AtLeast(ILits voc, IVecInt ps, int degree)

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".
static Constr	atLeastNew(UnitPropagationListener s, ILits voc, IVecInt ps, int n)
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.
protected static int	niceParameters(UnitPropagationListener s, ILits voc, IVecInt ps, int deg)
boolean	propagate(UnitPropagationListener s, int p) Propagate the truth value of a literal in constraints in which that literal is falsified.
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 d) 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()
Constr	toConstraint() Allow to access a constraint view of the propagatable to avoid casting.
String	toString() Textual representation of the constraint
void	undo(int p) Method called when backtracking

Methods inherited from class java.lang.Object

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

Field Detail

maxUnsatisfied

protected int maxUnsatisfied

number of allowed falsified literal

lits

protected final int[] lits

constraint literals

voc

protected final ILits voc

Constructor Detail

AtLeast

public AtLeast(ILits voc,
       IVecInt ps,
       int degree)

Parameters:

ps - a vector of literals

degree - the minimal number of satisfied literals

Method Detail

niceParameters

protected static int niceParameters(UnitPropagationListener s,
                 ILits voc,
                 IVecInt ps,
                 int deg)
                             throws ContradictionException

Throws:

ContradictionException

atLeastNew

public static Constr atLeastNew(UnitPropagationListener s,
                ILits voc,
                IVecInt ps,
                int n)
                         throws ContradictionException

Throws:

ContradictionException

Since:

2.1

remove

public void remove(UnitPropagationListener upl)

Description copied from interface: Constr

Remove a constraint from the solver.

Specified by:

remove in interface Constr

Since:

2.1

propagate

public boolean propagate(UnitPropagationListener s,
                int p)

Description copied from interface: Propagatable

Propagate the truth value of a literal in constraints in which that literal is falsified.

Specified by:

propagate in interface Propagatable

Parameters:

s - something able to perform unit propagation

p - the literal being propagated. Its negation must appear in the constraint.

Returns:

false iff an inconsistency (a contradiction) is detected.

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.

undo

public void undo(int p)

Description copied from interface: Undoable

Method called when backtracking

Specified by:

undo in interface Undoable

Parameters:

p - a literal to be unassigned.

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.

learnt

public boolean learnt()

Specified by:

learnt in interface IConstr

Returns:

true iff the clause was learnt during the search

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.

setActivity

public void setActivity(double d)

Description copied from interface: Constr

Set the activity at a specific value

Specified by:

setActivity in interface Constr

Parameters:

d - the new activity

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

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.

setLearnt

public void setLearnt()

Description copied from interface: Constr

Mark a constraint as learnt.

Specified by:

setLearnt in interface Constr

register

public void register()

Description copied from interface: Constr

Register the constraint to the solver.

Specified by:

register in interface Constr

size

public int size()

Specified by:

size in interface IConstr

Returns:

the number of literals in the constraint.

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

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.

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.

toString

public String toString()

Textual representation of the constraint

Overrides:

toString in class Object

Returns:

a string representing the constraint.

forwardActivity

public void forwardActivity(double claInc)

Specified by:

forwardActivity in interface Constr

Since:

2.1

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.

toConstraint

public Constr toConstraint()

Description copied from interface: Propagatable

Allow to access a constraint view of the propagatable to avoid casting. In most cases, the constraint will implement directly propagatable thus will return itself. It will also also the implementation of more sophisticated watching strategy.

Specified by:

toConstraint in interface Propagatable

Returns:

the constraint associated to that propagatable.

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.