org.chocosolver.solver.constraints.set

Class PropAtMost1Empty

java.lang.Object

org.chocosolver.solver.constraints.Propagator<SetVar>

org.chocosolver.solver.constraints.set.PropAtMost1Empty

All Implemented Interfaces:

Comparable<Propagator>, ICause, Identity

public class PropAtMost1Empty
extends Propagator<SetVar>

At most one set can be empty

Author:

Jean-Guillaume Fages

Field Summary

Fields inherited from class org.chocosolver.solver.constraints.Propagator

ACTIVE, constraint, model, NEW, PASSIVE, priority, reactToFineEvt, REIFIED, vars

Constructor Summary

Constructors

Constructor and Description
PropAtMost1Empty(SetVar[] sets) At most one set in the array sets can be empty

Method Summary

Modifier and Type	Method and Description
int	getPropagationConditions(int vIdx) Returns the specific mask indicating the variable events on which this Propagator object can react.
ESat	isEntailed() Check wether this is entailed according to the current state of its internal structure.
void	propagate(int evtmask) Call the main filtering algorithm to apply to the Domain of the Variable objects.
void	propagate(int v, int mask) Incremental filtering algorithm defined within the Propagator, called whenever the variable of index idxVarInProp has changed.

Methods inherited from class org.chocosolver.solver.constraints.Propagator

addVariable, arity, compareTo, defineIn, dynPriority, equals, fails, forcePropagate, forcePropagationOnBacktrack, getConstraint, getId, getModel, getNbVars, getPriority, getVar, getVars, getVIndices, hashCode, isActive, isCompletelyInstantiated, isPassive, isReifiedAndSilent, isStateLess, linkVariables, reactToFineEvent, setActive, setPassive, setReifiedSilent, setReifiedTrue, setVIndices, toString, why

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

PropAtMost1Empty

public PropAtMost1Empty(SetVar[] sets)

At most one set in the array sets can be empty

Parameters:

sets - array of set variables

Method Detail

getPropagationConditions

public int getPropagationConditions(int vIdx)

Description copied from class: Propagator

Returns the specific mask indicating the variable events on which this Propagator object can react.
A mask is a bitwise OR operations over IEventType this can react on. For example, consider a propagator that can deduce filtering based on the lower bound of the integer variable X. Then, for this variable, the mask should be equal to :

     int mask = IntEventType.INCLOW.getMask() | IntEventType.INSTANTIATE.getMask();
 

or, in a more convenient way:

     int mask = IntEvtType.combine(IntEventType.INCLOW,IntEventType.INSTANTIATE);
 

That indicates the following behavior:

1. if X is instantiated, this propagator will be executed,
2. if the lower bound of X is modified, this propagator will be executed,
3. if the lower bound of X is removed, the event is promoted from REMOVE to INCLOW and this propagator will NOT be executed,
4. otherwise, this propagator will NOT be executed

Some combinations are valid. For example, a propagator which reacts on REMOVE and INSTANTIATE should also declare INCLOW and DECUPP as conditions. Indeed INCLOW (resp. DECUPP), for efficiency purpose, removing the lower bound (resp. upper bound) of an integer variable will automatically be promoted into INCLOW (resp. DECUPP). So, ignoring INCLOW and/or DECUPP in that case may result in a lack of filtering. The same goes with events of other variable types, but most of the time, there are only few combinations. Reacts to any kind of event by default. Alternatively, this method can return IntEventType.VOID which states that this propagator should not be aware of modifications applied to the variable in position vIdx.

Overrides:

getPropagationConditions in class Propagator<SetVar>

Parameters:

vIdx - index of the variable within the propagator

Returns:

an int composed of REMOVE and/or INSTANTIATE and/or DECUPP and/or INCLOW

propagate

public void propagate(int evtmask)
               throws ContradictionException

Description copied from class: Propagator

Call the main filtering algorithm to apply to the Domain of the Variable objects. It considers the current state of this objects to remove some values from domains and/or instantiate some variables. Calling this method is done from 2 (and only 2) steps:
- at the initial propagation step,
- when involved in a reified constraint.
It should initialized the internal data structure and apply filtering algorithm from scratch.

Specified by:

propagate in class Propagator<SetVar>

Parameters:

evtmask - type of propagation event this must consider.

Throws:

ContradictionException - when a contradiction occurs, like domain wipe out or other incoherencies.

propagate

public void propagate(int v,
                      int mask)
               throws ContradictionException

Description copied from class: Propagator

Incremental filtering algorithm defined within the Propagator, called whenever the variable of index idxVarInProp has changed. This method calls a CUSTOM_PROPAGATION (coarse-grained) by default.

This method should be overridden if the argument reactToFineEvt is set to true in the constructor. Otherwise, it executes propagate(PropagatorEventType.CUSTOM_PROPAGATION.getStrengthenedMask());

Overrides:

propagate in class Propagator<SetVar>

Parameters:

v - index of the variable var in this

mask - type of event

Throws:

ContradictionException - if a contradiction occurs

isEntailed

public ESat isEntailed()

Description copied from class: Propagator

Check wether this is entailed according to the current state of its internal structure. At least, should check the satisfaction of this (when all is instantiated).

Specified by:

isEntailed in class Propagator<SetVar>

Returns:

ESat.TRUE if entailed, ESat.FALSE if not entailed, ESat.UNDEFINED if unknown