ttsolver.constraint
Class GroupConstraint

java.lang.Object
  ifs.model.Constraint
      ttsolver.constraint.GroupConstraint

public class GroupConstraint
extends Constraint

Group constraint.
This constraint expresses relations between several classes, e.g., that two sections of the same lecture can not be taught at the same time, or that some classes have to be taught one immediately after another. It can be either hard or soft.

Following constraints are now supported:

Constraint
SAME_TIME	Same time: given classes have to be taught in the same hours. If the classes are of different length, the smaller one cannot start before the longer one and it cannot end after the longer one.
SAME_DAYS	Same days: given classes have to be taught in the same day. If the classes are of different time patterns, the days of one class have to form a subset of the days of the other class.
BTB	Back-to-back constraint: given classes have to be taught in the same room and they have to follow one strictly after another.
BTB_TIME	Back-to-back constraint: given classes have to follow one strictly after another, but they can be taught in different rooms.
DIFF_TIME	Different time: given classes cannot overlap in time.
NHB(1), NHB(1.5), NHB(2), ... NHB(8)	Number of hours between: between the given classes, the exact number of hours have to be kept.
SAME_START	Same starting hour: given classes have to start in the same hour.
SAME_ROOM	Same room: given classes have to be placed in the same room.
NHB_GTE(1)	Greater than or equal to 1 hour between: between the given classes, the number of hours have to be one or more.
NHB_LT(6)	Less than 6 hours between: between the given classes, the number of hours have to be less than six.

Version:

1.0

Author:

Tomáš Müller

Field Summary

static int	TYPE_BTB Back-to-back constraint: given classes have to be taught in the same room and they have to follow one strictly after another.
static int	TYPE_BTB_TIME Back-to-back constraint: given classes have to follow one strictly after another, but they can be taught in different rooms.
static int	TYPE_DIFF_TIME Different time: given classes cannot overlap in time.
static int	TYPE_NHB_1 One hour between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_1_5 One and half hour between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_2 Two hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_3 Three hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_4 Four hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_4_5 Four and half hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_5 Five hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_6 Six hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_7 Seven hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_8 Eight hours between: between the given classes, the exact number of hours have to be kept.
static int	TYPE_NHB_GTE_1 Greater than or equal to 1 hour between: between the given classes, the number of hours have to be one or more.
static int	TYPE_NHB_LT_6 Less than 6 hours between: between the given classes, the number of hours have to be less than six.
static int	TYPE_SAME_DAYS Same days: given classes have to be taught in the same day.
static int	TYPE_SAME_ROOM Same room: given classes have to placed in the same room.
static int	TYPE_SAME_START Same room: given classes have to placed in the same room.
static int	TYPE_SAME_TIME Same time: given classes have to be taught in the same hours.

Constructor Summary

GroupConstraint(long id, int type, String preference)
Constructor

GroupConstraint(long id, String type, String preference)
Constructor

Method Summary

void	assigned(long iteration, Value value) Given value is to be assigned to its varable.
void	computeConflicts(Value value, Set conflicts) The only method which has to be implemented by any constraint.
int	getCurrentPreference() Current constraint preference (0 if prohibited or reqired, depends on current satisfaction of the constraint)
int	getCurrentPreference(Placement placement) Current constraint preference (if given placement is assigned)
String	getDescription() Constraint's description -- for printing purposes
Counter	getGlobalPreference() Global preference counter
long	getId() Constraint id
String	getName() Constraint's name -- for printing purposes
int	getPreference() Constraint preference (0 if prohibited or reqired)
String	getPrologPreference() Prolog reference: "R" for required, "P" for prohibited", "-2",.."2" for preference
int	getType() Constraint type (e.g, TYPE_SAME_TIME
String	getTypeStr() Constraint type (e.g, "SAME_TIME")
boolean	inConflict(Value value) Returns true if the given assignment is inconsistent with the existing assignments respecting this constraint.
boolean	isConsistent(Value value1, Value value2) Returns true if the given assignments are consistent respecting this constraint.
boolean	isHard() Returns true if the constraint is hard.
boolean	isProhibited() Is constraint prohibited
boolean	isRequired() Is constraint required
void	setGlobalPreference(Counter globalPreference) Global preference counter
String	toString()
void	unassigned(long iteration, Value value) Given value is unassigned from its varable.

Methods inherited from class ifs.model.Constraint

addConstraintListener, addVariable, assignedVariables, countAssignedVariables, countVariables, getInfo, getModel, hashCode, removeConstraintListener, removeVariable, setModel, variables

Methods inherited from class java.lang.Object

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

Field Detail

TYPE_SAME_TIME

public static int TYPE_SAME_TIME

Same time: given classes have to be taught in the same hours. If the classes are of different length, the smaller one cannot start before the longer one and it cannot end after the longer one.

TYPE_SAME_DAYS

public static int TYPE_SAME_DAYS

Same days: given classes have to be taught in the same day. If the classes are of different time patterns, the days of one class have to form a subset of the days of the other class.

TYPE_BTB

public static int TYPE_BTB

Back-to-back constraint: given classes have to be taught in the same room and they have to follow one strictly after another.

TYPE_BTB_TIME

public static int TYPE_BTB_TIME

Back-to-back constraint: given classes have to follow one strictly after another, but they can be taught in different rooms.

TYPE_DIFF_TIME

public static int TYPE_DIFF_TIME

Different time: given classes cannot overlap in time.

TYPE_NHB_1

public static int TYPE_NHB_1

One hour between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_2

public static int TYPE_NHB_2

Two hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_3

public static int TYPE_NHB_3

Three hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_4

public static int TYPE_NHB_4

Four hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_5

public static int TYPE_NHB_5

Five hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_6

public static int TYPE_NHB_6

Six hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_7

public static int TYPE_NHB_7

Seven hours between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_8

public static int TYPE_NHB_8

Eight hours between: between the given classes, the exact number of hours have to be kept.

TYPE_SAME_START

public static int TYPE_SAME_START

Same room: given classes have to placed in the same room.

TYPE_SAME_ROOM

public static int TYPE_SAME_ROOM

Same room: given classes have to placed in the same room.

TYPE_NHB_GTE_1

public static int TYPE_NHB_GTE_1

Greater than or equal to 1 hour between: between the given classes, the number of hours have to be one or more.

TYPE_NHB_LT_6

public static int TYPE_NHB_LT_6

Less than 6 hours between: between the given classes, the number of hours have to be less than six.

TYPE_NHB_1_5

public static int TYPE_NHB_1_5

One and half hour between: between the given classes, the exact number of hours have to be kept.

TYPE_NHB_4_5

public static int TYPE_NHB_4_5

Four and half hours between: between the given classes, the exact number of hours have to be kept.

Constructor Detail

GroupConstraint

public GroupConstraint(long id,
                       int type,
                       String preference)

Constructor

Parameters:

id - constraint id

type - constraint type (e.g, TYPE_SAME_TIME)

preference - time preferent ("R" for required, "P" for prohibited, "-2", "-1", "1", "2" for soft preference)

GroupConstraint

public GroupConstraint(long id,
                       String type,
                       String preference)

Constructor

Parameters:

id - constraint id

type - constraint type (e.g, "SAME_TIME")

preference - time preferent ("R" for required, "P" for prohibited, "-2", "-1", "1", "2" for soft preference)

Method Detail

getId

public long getId()

Constraint id

Overrides:

getId in class Constraint

getType

public int getType()

Constraint type (e.g, TYPE_SAME_TIME

getTypeStr

public String getTypeStr()

Constraint type (e.g, "SAME_TIME")

isRequired

public boolean isRequired()

Is constraint required

isProhibited

public boolean isProhibited()

Is constraint prohibited

getPrologPreference

public String getPrologPreference()

Prolog reference: "R" for required, "P" for prohibited", "-2",.."2" for preference

setGlobalPreference

public void setGlobalPreference(Counter globalPreference)

Global preference counter

getGlobalPreference

public Counter getGlobalPreference()

Global preference counter

isConsistent

public boolean isConsistent(Value value1,
                            Value value2)

Description copied from class: Constraint

Returns true if the given assignments are consistent respecting this constraint. This method is used by MAC (see MacPropagation).

Overrides:

isConsistent in class Constraint

computeConflicts

public void computeConflicts(Value value,
                             Set conflicts)

Description copied from class: Constraint

The only method which has to be implemented by any constraint. It returns the values which needs to be unassigned in order to make this constraint consistent with the given value if it is assigned to its variable. The computed list of conflicting values is added to the given set of conflicts.

Specified by:

computeConflicts in class Constraint

Parameters:

value - value to be assigned to its varaible

conflicts - resultant set of conflicting values

inConflict

public boolean inConflict(Value value)

Description copied from class: Constraint

Returns true if the given assignment is inconsistent with the existing assignments respecting this constraint. This method is used by MAC (see MacPropagation).

Overrides:

inConflict in class Constraint

getPreference

public int getPreference()

Constraint preference (0 if prohibited or reqired)

getCurrentPreference

public int getCurrentPreference()

Current constraint preference (0 if prohibited or reqired, depends on current satisfaction of the constraint)

getCurrentPreference

public int getCurrentPreference(Placement placement)

Current constraint preference (if given placement is assigned)

unassigned

public void unassigned(long iteration,
                       Value value)

Description copied from class: Constraint

Given value is unassigned from its varable.

Overrides:

unassigned in class Constraint

assigned

public void assigned(long iteration,
                     Value value)

Description copied from class: Constraint

Given value is to be assigned to its varable. In this method, the constraint should unassigns all varaibles which are in conflict with the given assignment because of this constraint.

Overrides:

assigned in class Constraint

toString

public String toString()

Overrides:

toString in class Object

isHard

public boolean isHard()

Description copied from class: Constraint

Returns true if the constraint is hard. Only hard constraints are allowed to unassign a variable when there is a conflict with a value that is being assigned

Overrides:

isHard in class Constraint

getName

public String getName()

Description copied from class: Constraint

Constraint's name -- for printing purposes

Overrides:

getName in class Constraint

getDescription

public String getDescription()

Description copied from class: Constraint

Constraint's description -- for printing purposes

Overrides:

getDescription in class Constraint