org.jacop.constraints.binpacking

Class Binpacking

java.lang.Object

org.jacop.constraints.DecomposedConstraint<Constraint>

org.jacop.constraints.Constraint

org.jacop.constraints.binpacking.Binpacking

All Implemented Interfaces:

SatisfiedPresent, Stateful, UsesQueueVariable

public class Binpacking
extends Constraint
implements UsesQueueVariable, Stateful, SatisfiedPresent

Binpacking constraint implements bin packing problem. It ensures that items are packed into bins while respecting cpacity constraints of each bin.

This implementation is based on paper "A Constraint for Bin Packing" by Paul Shaw, CP 2004.

This constraint is not idempotent (does not compute fix-point) and, in case when another computation for fix-point is needed, it adds itself to the constraint queue.

Version:

4.9

Author:

Krzysztof Kuchcinski and Radoslaw Szymanek

Field Summary

Fields

Modifier and Type	Field and Description
org.jacop.constraints.binpacking.BinItem[]	item It keeps together a list of variables which define bin for item i and their weigts.
IntVar[]	load It specifies a list of variables which define bin load.

Fields inherited from class org.jacop.constraints.Constraint

atomicExecution, consistencyPruningEvents, constraintScope, earlyTerminationOK, increaseWeight, numberId, scope, trace

Fields inherited from class org.jacop.constraints.DecomposedConstraint

queueIndex

Constructor Summary

Constructors

Constructor and Description
Binpacking(IntVar[] bin, IntVar[] load, int[] w) It constructs the binpacking constraint for the supplied variable.
Binpacking(IntVar[] bin, IntVar[] load, int[] w, int minBin) It constructs the binpacking constraint for the supplied variable.
Binpacking(IntVar[] bin, IntVar[] load, int[] w, int minBin, boolean LBpruning)
Binpacking(List<? extends IntVar> bin, List<? extends IntVar> load, int[] w) It constructs the binpacking constraint for the supplied variable.
Binpacking(List<? extends IntVar> bin, List<? extends IntVar> load, int[] w, int minBin) It constructs the binpacking constraint for the supplied variable.

Method Summary

Modifier and Type	Method and Description
void	consistency(Store store) It is a (most probably incomplete) consistency function which removes the values from variables domains.
int	getDefaultConsistencyPruningEvent()
void	impose(Store store) It imposes the constraint in a given store.
void	queueVariable(int level, Var var) This is a function called to indicate which variable in a scope of constraint has changed.
void	removeLevel(int level) This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid.
boolean	satisfied() It checks if the constraint is satisfied.
String	toString() It produces a string representation of a constraint state.

Methods inherited from class org.jacop.constraints.Constraint

afc, arguments, cleanAfterFailure, decompose, getConsistencyPruningEvent, getGuideConstraint, getGuideValue, getGuideVariable, grounded, grounded, id, impose, imposeDecomposition, increaseWeight, intArrayToString, long2int, numberArgs, removeConstraint, requiresMonotonicity, setConsistencyPruningEvent, setConstraintScope, setScope, setScope, setScope, setScope, setScope, setWatchedVariableGrounded, supplyGuideFeedback, updateAFC, watchedVariableGrounded

Methods inherited from class org.jacop.constraints.DecomposedConstraint

auxiliaryVariables, checkInput, checkInput, checkInputForDuplication, checkInputForDuplicationSkipSingletons, checkInputForNullness, checkInputForNullness, checkInputForNullness, derivative, getDubletonsSkipSingletons, imposeDecomposition

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.jacop.api.Stateful

isStateful

Field Detail

item

public final org.jacop.constraints.binpacking.BinItem[] item

It keeps together a list of variables which define bin for item i and their weigts.

load

public final IntVar[] load

It specifies a list of variables which define bin load.

Constructor Detail

Binpacking

public Binpacking(IntVar[] bin,
                  IntVar[] load,
                  int[] w)

It constructs the binpacking constraint for the supplied variable.

Parameters:

bin - which are constrained to define bin for item i.

load - which are constrained to define load for bin i.

w - which define size ofitem i.

Binpacking

public Binpacking(List<? extends IntVar> bin,
                  List<? extends IntVar> load,
                  int[] w)

It constructs the binpacking constraint for the supplied variable.

Parameters:

bin - which are constrained to define bin for item i.

load - which are constrained to define load for bin i.

w - which define size ofitem i.

Binpacking

public Binpacking(IntVar[] bin,
                  IntVar[] load,
                  int[] w,
                  int minBin)

It constructs the binpacking constraint for the supplied variable.

Parameters:

bin - which are constrained to define bin for item i.

load - which are constrained to define load for bin i.

w - which define size ofitem i.

minBin - minimal index of a bin; ovewrite the value provided by minimal index of variable bin

Binpacking

public Binpacking(List<? extends IntVar> bin,
                  List<? extends IntVar> load,
                  int[] w,
                  int minBin)

It constructs the binpacking constraint for the supplied variable.

Parameters:

bin - which are constrained to define bin for item i.

load - which are constrained to define load for bin i.

w - which define size ofitem i.

minBin - minimal index of a bin; ovewrite the value provided by minimal index of variable bin

Binpacking

public Binpacking(IntVar[] bin,
                  IntVar[] load,
                  int[] w,
                  int minBin,
                  boolean LBpruning)

Method Detail

impose

public void impose(Store store)

Description copied from class: Constraint

It imposes the constraint in a given store.

Overrides:

impose in class Constraint

Parameters:

store - the constraint store to which the constraint is imposed to.

consistency

public void consistency(Store store)

Description copied from class: Constraint

It is a (most probably incomplete) consistency function which removes the values from variables domains. Only values which do not have any support in a solution space are removed.

Specified by:

consistency in class Constraint

Parameters:

store - constraint store within which the constraint consistency is being checked.

getDefaultConsistencyPruningEvent

public int getDefaultConsistencyPruningEvent()

Specified by:

getDefaultConsistencyPruningEvent in class Constraint

satisfied

public boolean satisfied()

Description copied from interface: SatisfiedPresent

It checks if the constraint is satisfied. It can return false even if constraint is satisfied but not all variables in its scope are grounded. It needs to return true if all variables in its scope are grounded and constraint is satisfied.

Implementations of this interface for constraints that are not PrimitiveConstraint may require constraint imposition and consistency check as a requirement to work correctly.

Specified by:

satisfied in interface SatisfiedPresent

Returns:

true if constraint is possible to verify that it is satisfied.

queueVariable

public void queueVariable(int level,
                          Var var)

Description copied from class: Constraint

This is a function called to indicate which variable in a scope of constraint has changed. It also indicates a store level at which the change has occurred.

Overrides:

queueVariable in class Constraint

Parameters:

level - the level of the store at which the change has occurred.

var - variable which has changed.

removeLevel

public void removeLevel(int level)

Description copied from interface: Stateful

This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid. This function is called *before* all timestamps, variables, mutablevariables have reverted to their previous value.

Specified by:

removeLevel in interface Stateful

Parameters:

level - the level which is being removed.

toString

public String toString()

Description copied from class: Constraint

It produces a string representation of a constraint state.

Overrides:

toString in class Constraint