Module org.chocosolver.solver

Package org.chocosolver.solver.learn

Class LazyImplications

java.lang.Object

org.chocosolver.solver.learn.Implications

org.chocosolver.solver.learn.LazyImplications

public class LazyImplications
extends Implications

This implication graph is lazily built. It maintains the list of events invoked during propagation on each variable, and maintains a copy of each domain.

Data is stored in a stack, where each entry is a tuple:

< v, D, c, m, p, n>

where :

• v is the variable modified,
• D is its current domain,
• c is the cause (most of the time, a propagator),
• m is the mask of event that triggers the modification,
• p is a pointer to the previous entry on v in the stack
• n is a pointer to the next entry on v in the stack (if any)

Note that, under some conditions, two entries can be merged into a single one. Project: choco-solver.

Since:

25/01/2017.

Author:

Charles Prud'homme

Method Summary

Modifier and Type	Method	Description
void	collectNodesFromConflict(ContradictionException cft, ValueSortedMap<IntVar> front)	Fill set with indices of nodes that throws the conflict
void	copyComplementSet(IntVar var, IntIterableRangeSet set, IntIterableRangeSet dest)	Copy in dest the complement of set wrt to root domain of var
void	findPredecessor(ValueSortedMap<IntVar> front, IntVar vi, int p)	Find the direct predecessor of a node, declared on variable vi, starting from node at position p.
ICause	getCauseAt(int idx)	Get the ICause declared in node idx
int	getDecisionLevelAt(int idx)	Get the decision level declared in node idx
IntIterableRangeSet	getDomainAt(int idx)	Get the IntIterableRangeSet that represents domain declared in node idx
int	getEventMaskAt(int idx)	Get the mask of event declared in node idx.
IntVar	getIntVarAt(int idx)	Get the IntVar declared in node idx
int	getPredecessorOf(int idx)	Get the position of precedent entry of the one declared in node idx
IntIterableRangeSet	getRootDomain(IntVar var)	Get the IntIterableRangeSet that represents domain of this variables as declared in the model
int	getValueAt(int idx)	Get the value declared in node idx
void	init(Model model)	Initialize this class
void	predecessorsOf(int p, ValueSortedMap<IntVar> front)	Retrieve the nodes that are predecessors of node p in this and put them into set.
void	pushEvent(IntVar var, ICause cause, IntEventType evt, int one, int two, int three)	Push an event
void	reset()	Reset the model, set at its creation state, before calling Implications.init(Model).
int	size()
void	tagDecisionLevel()
void	undoLastEvent()	Undo the last event stored, use only when dealing with views.

Methods inherited from class java.lang.Object

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

Method Detail

init

public void init(Model model)

Description copied from class: Implications

Initialize this class

Specified by:

init in class Implications

Parameters:

model - if needed, a reference to the model that uses this class

reset

public void reset()

Description copied from class: Implications

Reset the model, set at its creation state, before calling Implications.init(Model).

Specified by:

reset in class Implications

tagDecisionLevel

public void tagDecisionLevel()

Specified by:

tagDecisionLevel in class Implications

undoLastEvent

public void undoLastEvent()

Description copied from class: Implications

Undo the last event stored, use only when dealing with views.

Specified by:

undoLastEvent in class Implications

pushEvent

public void pushEvent(IntVar var,
                      ICause cause,
                      IntEventType evt,
                      int one,
                      int two,
                      int three)

Description copied from class: Implications

Push an event

Specified by:

pushEvent in class Implications

Parameters:

var - modified variable

cause - cause of the modification

evt - modification mask

one - an int

two - an int

three - an int

size

public int size()

Specified by:

size in class Implications

Returns:

the number of nodes in the implication graph.

collectNodesFromConflict

public void collectNodesFromConflict(ContradictionException cft,
                                     ValueSortedMap<IntVar> front)

Description copied from class: Implications

Fill set with indices of nodes that throws the conflict

Specified by:

collectNodesFromConflict in class Implications

Parameters:

cft - the failure, in the form of a ContradictionException

front - (initially empty) map of (node, variable) in conflict

predecessorsOf

public void predecessorsOf(int p,
                           ValueSortedMap<IntVar> front)

Description copied from class: Implications

Retrieve the nodes that are predecessors of node p in this and put them into set.

Specified by:

predecessorsOf in class Implications

Parameters:

p - index of the node whom predecessors have to be found

front - map of (node, variable) in conflict

findPredecessor

public void findPredecessor(ValueSortedMap<IntVar> front,
                            IntVar vi,
                            int p)

Find the direct predecessor of a node, declared on variable vi, starting from node at position p. If a variable-based node already exists in front, then this node is used to look for the predecessor, assuming that it is below p (otherwise, this node the predecessor we are looking for). Otherwise, there is no node based on vi in front and the rightmost node above p, starting from the predecessor of its root node, is added.

Specified by:

findPredecessor in class Implications

Parameters:

front - the set to update

vi - the variable to look the predecessor for

p - the rightmost position of the node (below means outdated node).

getCauseAt

public ICause getCauseAt(int idx)

Description copied from class: Implications

Get the ICause declared in node idx

Specified by:

getCauseAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the cause declared in node idx

getEventMaskAt

public int getEventMaskAt(int idx)

Description copied from class: Implications

Get the mask of event declared in node idx. The mask can be a bitwise operation over mask of IntEventType.

Specified by:

getEventMaskAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the event declared in node idx

getIntVarAt

public IntVar getIntVarAt(int idx)

Description copied from class: Implications

Get the IntVar declared in node idx

Specified by:

getIntVarAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the intvar declared in node idx

getValueAt

public int getValueAt(int idx)

Description copied from class: Implications

Get the value declared in node idx

Specified by:

getValueAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the value declared in node idx

getDecisionLevelAt

public int getDecisionLevelAt(int idx)

Description copied from class: Implications

Get the decision level declared in node idx

Specified by:

getDecisionLevelAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the decision level declared in node idx

getDomainAt

public IntIterableRangeSet getDomainAt(int idx)

Description copied from class: Implications

Get the IntIterableRangeSet that represents domain declared in node idx

Specified by:

getDomainAt in class Implications

Parameters:

idx - position of the node to query

Returns:

the domain declared in node idx

getPredecessorOf

public int getPredecessorOf(int idx)

Description copied from class: Implications

Get the position of precedent entry of the one declared in node idx

Specified by:

getPredecessorOf in class Implications

Parameters:

idx - position of the node to query

Returns:

its ancestor

getRootDomain

public IntIterableRangeSet getRootDomain(IntVar var)

Description copied from class: Implications

Get the IntIterableRangeSet that represents domain of this variables as declared in the model

Specified by:

getRootDomain in class Implications

Parameters:

var - variable to query

Returns:

the domain declared in node idx

copyComplementSet

public void copyComplementSet(IntVar var,
                              IntIterableRangeSet set,
                              IntIterableRangeSet dest)

Description copied from class: Implications

Copy in dest the complement of set wrt to root domain of var

Specified by:

copyComplementSet in class Implications

Parameters:

var - variable to query