org.chocosolver.solver.constraints.nary.sum

Class PropSum

java.lang.Object

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

org.chocosolver.solver.constraints.nary.sum.PropSum

All Implemented Interfaces:

Comparable<Propagator>, ICause, Identity

Direct Known Subclasses:

PropScalar, PropSumBool

public class PropSum
extends Propagator<IntVar>

A propagator for SUM(x_i) o b
Based on "Bounds Consistency Techniques for Long Linear Constraint"
W. Harvey and J. Schimpf

Since:

18/03/11

Author:

Charles Prud'homme

Field Summary

Fields

Modifier and Type	Field and Description
protected int	b Bound to respect
protected int[]	I Variability of each variable (ie domain amplitude)
protected int	l Number of variables
protected int	maxI Stores the maximal variability
protected Operator	o The operator among EQ, LE, GE and NE
protected int	pos The position of the last positive coefficient
protected int	sumLB SUm of lower bounds
protected int	sumUB Sum of upper bounds

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

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

Constructor Summary

Constructors

Constructor and Description
PropSum(IntVar[] variables, int pos, Operator o, int b) Creates a sum propagator: SUM(x_i) o b Coefficients are induced by pos: those before pos (included) are equal to 1, the other ones are equal to -1.

Method Summary

Modifier and Type	Method and Description
protected ESat	check(int sumLB, int sumUB) Whether the current state of the scalar product is entailed
protected static PropagatorPriority	computePriority(int nbvars) Compute the priority of the propagator wrt the number of involved variables
protected void	filter() Execute filtering wrt the operator
protected void	filterOnEq() Apply filtering when operator is EQ
protected void	filterOnGeq() Apply filtering when operator is GE
protected void	filterOnLeq() Apply filtering when operator is LE
protected void	filterOnNeq() Apply filtering when operator is NE
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.
protected static int	nb(Operator co)
protected static Operator	nop(Operator co)
protected PropSum	opposite()
protected void	prepare() Prepare the propagation: compute sumLB, sumUB and I
void	propagate(int evtmask) Call the main filtering algorithm to apply to the Domain of the Variable objects.
String	toString()
boolean	why(RuleStore ruleStore, IntVar var, IEventType evt, int value) Add new rules to the rule store

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, propagate, reactToFineEvent, setActive, setPassive, setReifiedSilent, setReifiedTrue, setVIndices

Methods inherited from class java.lang.Object

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

Field Detail

pos

protected final int pos

The position of the last positive coefficient

l

protected final int l

Number of variables

b

protected final int b

Bound to respect

I

protected final int[] I

Variability of each variable (ie domain amplitude)

maxI

protected int maxI

Stores the maximal variability

sumLB

protected int sumLB

SUm of lower bounds

sumUB

protected int sumUB

Sum of upper bounds

o

protected final Operator o

The operator among EQ, LE, GE and NE

Constructor Detail

PropSum

public PropSum(IntVar[] variables,
               int pos,
               Operator o,
               int b)

Creates a sum propagator: SUM(x_i) o b Coefficients are induced by pos: those before pos (included) are equal to 1, the other ones are equal to -1.

Parameters:

variables - list of integer variables

pos - position of the last positive coefficient

o - operator amng EQ, LE, GE and NE

b - bound to respect

Method Detail

computePriority

protected static PropagatorPriority computePriority(int nbvars)

Compute the priority of the propagator wrt the number of involved variables

Parameters:

nbvars - number of variables

Returns:

the priority

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<IntVar>

Parameters:

vIdx - index of the variable within the propagator

Returns:

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

prepare

protected void prepare()

Prepare the propagation: compute sumLB, sumUB and I

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<IntVar>

Parameters:

evtmask - type of propagation event this must consider.

Throws:

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

filter

protected void filter()
               throws ContradictionException

Execute filtering wrt the operator

Throws:

ContradictionException - if contradiction is detected

filterOnEq

protected void filterOnEq()
                   throws ContradictionException

Apply filtering when operator is EQ

Throws:

ContradictionException - if contradiction is detected

filterOnLeq

protected void filterOnLeq()
                    throws ContradictionException

Apply filtering when operator is LE

Throws:

ContradictionException - if contradiction is detected

filterOnGeq

protected void filterOnGeq()
                    throws ContradictionException

Apply filtering when operator is GE

Throws:

ContradictionException - if contradiction is detected

filterOnNeq

protected void filterOnNeq()
                    throws ContradictionException

Apply filtering when operator is NE

Throws:

ContradictionException - if contradiction is detected

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<IntVar>

Returns:

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

check

protected ESat check(int sumLB,
                     int sumUB)

Whether the current state of the scalar product is entailed

Parameters:

sumLB - sum of lower bounds

sumUB - sum of upper bounds

Returns:

the entailment check

toString

public String toString()

Overrides:

toString in class Propagator<IntVar>

why

public boolean why(RuleStore ruleStore,
                   IntVar var,
                   IEventType evt,
                   int value)

Description copied from interface: ICause

Add new rules to the rule store

Specified by:

why in interface ICause

Overrides:

why in class Propagator<IntVar>

Parameters:

ruleStore - the rule store

var - the modified variable

evt - the undergoing event

value - the value (for REMOVE only)

Returns:

true if at least one rule has been added to the rule store

nb

protected static int nb(Operator co)

nop

protected static Operator nop(Operator co)

opposite

protected PropSum opposite()