org.cpsolver.coursett.constraint

Class JenrlConstraint

java.lang.Object

org.cpsolver.ifs.model.Constraint<V,T>

org.cpsolver.ifs.model.BinaryConstraint<V,T>

org.cpsolver.ifs.assignment.context.BinaryConstraintWithContext<Lecture,Placement,JenrlConstraint.JenrlConstraintContext>

org.cpsolver.coursett.constraint.JenrlConstraint

All Implemented Interfaces:

Comparable<Constraint<Lecture,Placement>>, CanHoldContext, HasAssignmentContext<Lecture,Placement,JenrlConstraint.JenrlConstraintContext>, WeakeningConstraint<Lecture,Placement>

public class JenrlConstraint
extends BinaryConstraintWithContext<Lecture,Placement,JenrlConstraint.JenrlConstraintContext>
implements WeakeningConstraint<Lecture,Placement>

Join student enrollment constraint.
This constraint is placed between all pairs of classes where there is at least one student attending both classes. It represents a number of student conflicts (number of joined enrollments), if the given two classes overlap in time.
Also, it dynamically maintains the counter of all student conflicts. It is a soft constraint.

Version:

CourseTT 1.3 (University Course Timetabling)
Copyright (C) 2006 - 2014 Tomáš Müller
muller@unitime.org
http://muller.unitime.org

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not see http://www.gnu.org/licenses/.

Author:

Tomáš Müller

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	JenrlConstraint.JenrlConstraintContext

Field Summary

Fields inherited from class org.cpsolver.ifs.model.Constraint

iConstraintListeners, iId

Fields inherited from interface org.cpsolver.ifs.assignment.context.CanHoldContext

sMaxSize

Constructor Summary

Constructors

Constructor and Description
JenrlConstraint() Constructor

Method Summary

Modifier and Type	Method and Description
boolean	areStudentConflictsCommitted()
boolean	areStudentConflictsDistance(Assignment<Lecture,Placement> assignment)
boolean	areStudentConflictsDistance(Assignment<Lecture,Placement> assignment, Placement value)
boolean	areStudentConflictsHard()
boolean	areStudentConflictsWorkday(Assignment<Lecture,Placement> assignment, Placement value)
void	computeConflicts(Assignment<Lecture,Placement> assignment, Placement value, Set<Placement> conflicts) The only method which has to be implemented by any constraint.
JenrlConstraint.JenrlConstraintContext	createAssignmentContext(Assignment<Lecture,Placement> assignment) Create a new assignment context for the given assignment.
void	decJenrl(Assignment<Lecture,Placement> assignment, Student student) Decrement the number of joined enrollments (during student final sectioning)
Set<Student>	getInstructors()
long	getJenrl() Number of joined enrollments (during student final sectioning)
double	getJenrlWeight(Student student)
String	getName() Constraint's name -- for printing purposes
int	getNrInstructors()
int	getNrStudents()
Set<Student>	getStudents()
void	incJenrl(Assignment<Lecture,Placement> assignment, Student student) Increment the number of joined enrollments (during student final sectioning)
boolean	inConflict(Assignment<Lecture,Placement> assignment, Placement value) Returns true if the given assignment is inconsistent with the existing assignments respecting this constraint.
boolean	isHard() Returns true if the constraint is hard.
boolean	isInConflict(Assignment<Lecture,Placement> assignment) True if the given two lectures overlap in time
static boolean	isInConflict(Placement p1, Placement p2, DistanceMetric m, int workDayLimit) Returns true if the given placements are overlapping or they are back-to-back and too far for students.
boolean	isOfTheSameProblem()
boolean	isToBeIgnored() Returns true if there is IgnoreStudentConflictsConstraint between the two lectures.
double	jenrl()
long	jenrl(Assignment<Lecture,Placement> assignment, Lecture variable, Placement value) Number of joined enrollments if the given value is assigned to the given variable
double	priority()
void	setModel(Model<Lecture,Placement> model) Sets the model which the constraint belongs to
String	toString()
void	weaken(Assignment<Lecture,Placement> assignment) Weaken the constraint.
void	weaken(Assignment<Lecture,Placement> assignment, Placement value) Weaken the constraint enough so that it can assign the given value.

Methods inherited from class org.cpsolver.ifs.assignment.context.BinaryConstraintWithContext

assigned, getAssignmentContextReference, getContext, getContext, setAssignmentContextReference, unassigned

Methods inherited from class org.cpsolver.ifs.model.BinaryConstraint

addVariable, another, first, isFirst, second

Methods inherited from class org.cpsolver.ifs.model.Constraint

addConstraintListener, assignedVariables, compareTo, computeConflictsNoForwardCheck, constraintListeners, countAssignedVariables, countVariables, equals, getDescription, getId, getModel, hashCode, isConsistent, removeConstraintListener, removeVariable, variables

Methods inherited from class java.lang.Object

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

Constructor Detail

JenrlConstraint

public JenrlConstraint()

Constructor

Method Detail

setModel

public void setModel(Model<Lecture,Placement> model)

Description copied from class: Constraint

Sets the model which the constraint belongs to

Overrides:

setModel in class BinaryConstraintWithContext<Lecture,Placement,JenrlConstraint.JenrlConstraintContext>

Parameters:

model - problem model

computeConflicts

public void computeConflicts(Assignment<Lecture,Placement> assignment,
                             Placement value,
                             Set<Placement> 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<Lecture,Placement>

Parameters:

assignment - current assignment

value - value to be assigned to its variable

conflicts - resultant set of conflicting values

inConflict

public boolean inConflict(Assignment<Lecture,Placement> assignment,
                          Placement 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<Lecture,Placement>

Parameters:

assignment - current assignment

value - given value

Returns:

true if there is a conflict with other assigned variables of the constraint

isInConflict

public static boolean isInConflict(Placement p1,
                                   Placement p2,
                                   DistanceMetric m,
                                   int workDayLimit)

Returns true if the given placements are overlapping or they are back-to-back and too far for students.

Parameters:

p1 - first placement

p2 - second placement

m - distance metrics

workDayLimit - limit on the work-day

Returns:

true if there is a student conflict between the two placements

jenrl

public long jenrl(Assignment<Lecture,Placement> assignment,
                  Lecture variable,
                  Placement value)

Number of joined enrollments if the given value is assigned to the given variable

Parameters:

assignment - current assignment

variable - a class

value - class placement under consideration

Returns:

number of student conflicts caused by this constraint if assigned

isInConflict

public boolean isInConflict(Assignment<Lecture,Placement> assignment)

True if the given two lectures overlap in time

Parameters:

assignment - current assignment

Returns:

true if this constraint is conflicting

incJenrl

public void incJenrl(Assignment<Lecture,Placement> assignment,
                     Student student)

Increment the number of joined enrollments (during student final sectioning)

Parameters:

assignment - current assignment

student - student added in between the two classes of this constraint

getJenrlWeight

public double getJenrlWeight(Student student)

decJenrl

public void decJenrl(Assignment<Lecture,Placement> assignment,
                     Student student)

Decrement the number of joined enrollments (during student final sectioning)

Parameters:

assignment - current assignment

student - student removed from between the two classes of this constraint

getJenrl

public long getJenrl()

Number of joined enrollments (during student final sectioning)

Returns:

number of joined enrollments

jenrl

public double jenrl()

priority

public double priority()

getNrStudents

public int getNrStudents()

getStudents

public Set<Student> getStudents()

getNrInstructors

public int getNrInstructors()

getInstructors

public Set<Student> getInstructors()

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<Lecture,Placement>

Returns:

true if the constraint is hard

getName

public String getName()

Description copied from class: Constraint

Constraint's name -- for printing purposes

Overrides:

getName in class Constraint<Lecture,Placement>

Returns:

constraint name

toString

public String toString()

Overrides:

toString in class Object

areStudentConflictsHard

public boolean areStudentConflictsHard()

areStudentConflictsDistance

public boolean areStudentConflictsDistance(Assignment<Lecture,Placement> assignment)

areStudentConflictsCommitted

public boolean areStudentConflictsCommitted()

areStudentConflictsDistance

public boolean areStudentConflictsDistance(Assignment<Lecture,Placement> assignment,
                                           Placement value)

areStudentConflictsWorkday

public boolean areStudentConflictsWorkday(Assignment<Lecture,Placement> assignment,
                                          Placement value)

isOfTheSameProblem

public boolean isOfTheSameProblem()

weaken

public void weaken(Assignment<Lecture,Placement> assignment)

Description copied from interface: WeakeningConstraint

Weaken the constraint. This method is called if the constraint participates in an unassigned of a variable.

Specified by:

weaken in interface WeakeningConstraint<Lecture,Placement>

Parameters:

assignment - current assignment

weaken

public void weaken(Assignment<Lecture,Placement> assignment,
                   Placement value)

Description copied from interface: WeakeningConstraint

Weaken the constraint enough so that it can assign the given value.

Specified by:

weaken in interface WeakeningConstraint<Lecture,Placement>

Parameters:

assignment - current assignment

value - a conflicting value to be assigned

isToBeIgnored

public boolean isToBeIgnored()

Returns true if there is IgnoreStudentConflictsConstraint between the two lectures.

Returns:

true if this constraint is to be ignored

createAssignmentContext

public JenrlConstraint.JenrlConstraintContext createAssignmentContext(Assignment<Lecture,Placement> assignment)

Description copied from interface: HasAssignmentContext

Create a new assignment context for the given assignment. If there are already some variables assigned in the value, the method should make sure that the context is appropriately initialized.

Specified by:

createAssignmentContext in interface HasAssignmentContext<Lecture,Placement,JenrlConstraint.JenrlConstraintContext>

Parameters:

assignment - an assignment for which there needs to be an assignment context

Returns:

a new instance of the assignment context, filled according to the given assignment