org.chocosolver.solver.propagation

Class PropagationEngine

java.lang.Object

org.chocosolver.solver.propagation.PropagationEngine

public class PropagationEngine
extends Object

This engine is priority-driven constraint-oriented seven queues engine.
On a call to onVariableUpdate, it stores the event generated and schedules the propagator in one of the 7 queues wrt to its priority for future revision.

Since:

05/07/12

Author:

Charles Prud'homme

Field Summary

Fields

Modifier and Type	Field and Description
static boolean	CHECK_SCOPE

Constructor Summary

Constructors

Constructor and Description
PropagationEngine(Model model) A seven-queue propagation engine.

Method Summary

Modifier and Type	Method and Description
void	clear() Clear internal structures
void	delayedPropagation(Propagator propagator, PropagatorEventType type) Exeucte a delayed propagator
void	desactivatePropagator(Propagator propagator) Set the propagator as inactivated within the propagation engine
void	dynamicAddition(boolean permanent, Propagator... ps) Add a constraint to the propagation engine
void	dynamicDeletion(Propagator... ps) Delete the list of propagators in input from the engine
void	execute(Propagator propagator) Execute 'coarse' propagation on a newly added propagator or one that should be propagated on backtrack
void	flush() Flush this, ie.
void	ignoreModifications()
void	initialize() Build up internal structure, if not yet done, in order to allow propagation.
boolean	isInitialized() Is the engine initialized? Important for dynamic addition of constraints
void	onPropagatorExecution(Propagator propagator) Action to do when a propagator is executed
void	onVariableUpdate(Variable variable, IEventType type, ICause cause) Take into account the modification of a variable
void	propagate() Launch the proapagation, ie, active propagators if necessary, then reach a fix point
void	propagateOnBacktrack(Propagator propagator) Update the scope of variable of a propagator (addition or deletion are allowed -- p.vars are scanned)
void	reset() Reset the propagation engine.
void	updateInvolvedVariables(Propagator p) Update the scope of variable of a propagator (addition or deletion are allowed -- p.vars are scanned)

Methods inherited from class java.lang.Object

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

Field Detail

CHECK_SCOPE

public static boolean CHECK_SCOPE

Constructor Detail

PropagationEngine

public PropagationEngine(Model model)

A seven-queue propagation engine. Each of the seven queues deals with on priority. When a propagator needs to be executed, it is scheduled in the queue corresponding to its priority. The lowest priority queue is emptied before one element of the second lowest queue is popped, etc.

Parameters:

model - the declaring model

Method Detail

initialize

public void initialize()
                throws SolverException

Build up internal structure, if not yet done, in order to allow propagation. If new constraints are added after having initializing the engine, dynamic addition is used. A call to clear erase the internal structure, and allow new initialisation.

Throws:

SolverException - if a constraint is declared more than once in this propagation engine

isInitialized

public boolean isInitialized()

Is the engine initialized? Important for dynamic addition of constraints

Returns:

true if the engine has been initialized

propagate

public void propagate()
               throws ContradictionException

Launch the proapagation, ie, active propagators if necessary, then reach a fix point

Throws:

ContradictionException - if a contradiction occurrs

execute

public void execute(Propagator propagator)
             throws ContradictionException

Execute 'coarse' propagation on a newly added propagator or one that should be propagated on backtrack

Parameters:

propagator - a propagator to propagate

Throws:

ContradictionException - if propagation fails

flush

public void flush()

Flush this, ie. remove every pending events

onVariableUpdate

public void onVariableUpdate(Variable variable,
                             IEventType type,
                             ICause cause)

Take into account the modification of a variable

Parameters:

variable - modified variable

type - type of modification event

cause - origin of the modification

delayedPropagation

public void delayedPropagation(Propagator propagator,
                               PropagatorEventType type)
                        throws ContradictionException

Exeucte a delayed propagator

Parameters:

propagator - propagator to execute

type - type of event to execute

Throws:

ContradictionException - if a failure is encountered

onPropagatorExecution

public void onPropagatorExecution(Propagator propagator)

Action to do when a propagator is executed

Parameters:

propagator - propagator to execute

desactivatePropagator

public void desactivatePropagator(Propagator propagator)

Set the propagator as inactivated within the propagation engine

Parameters:

propagator - propagator to desactivate

reset

public void reset()

Reset the propagation engine.

clear

public void clear()

Clear internal structures

ignoreModifications

public void ignoreModifications()

dynamicAddition

public void dynamicAddition(boolean permanent,
                            Propagator... ps)
                     throws SolverException

Add a constraint to the propagation engine

Parameters:

permanent - does the constraint is permanently added

ps - propagators to add * @throws SolverException if a constraint is declared more than once in this propagation engine

Throws:

SolverException

updateInvolvedVariables

public void updateInvolvedVariables(Propagator p)

Update the scope of variable of a propagator (addition or deletion are allowed -- p.vars are scanned)

Parameters:

p - a propagator

propagateOnBacktrack

public void propagateOnBacktrack(Propagator propagator)

Update the scope of variable of a propagator (addition or deletion are allowed -- p.vars are scanned)

Parameters:

propagator - a propagator

dynamicDeletion

public void dynamicDeletion(Propagator... ps)

Delete the list of propagators in input from the engine

Parameters:

ps - a list of propagators