org.cpsolver.coursett.heuristics

Class LectureSelection

java.lang.Object

org.cpsolver.coursett.heuristics.LectureSelection

All Implemented Interfaces:

VariableSelection<Lecture,Placement>

public class LectureSelection
extends Object
implements VariableSelection<Lecture,Placement>

Lecture (variable) selection.

If there are one or more variables unassigned, the variable selection criterion picks one of them randomly. We have tried several approaches using domain sizes, number of previous assignments, numbers of constraints in which the variable participates, etc., but there was no significant improvement in this timetabling problem towards the random selection of an unassigned variable. The reason is, that it is easy to go back when a wrong variable is picked - such a variable is unassigned when there is a conflict with it in some of the subsequent iterations.

When all variables are assigned, an evaluation is made for each variable according to the above described weights. The variable with the worst evaluation is selected. This variable promises the best improvement in optimization.

Parameters (selection among unassigned lectures):

Related Solver Parameters

Parameter	Type	Comment
Lecture.RouletteWheelSelection	Boolean	Roulette wheel selection
Lecture.RandomWalkProb	Double	Random walk probability
Lecture.DomainSizeWeight	Double	Domain size weight
Lecture.NrAssignmentsWeight	Double	Number of assignments weight
Lecture.InitialAssignmentWeight	Double	Initial assignment weight
Lecture.NrConstraintsWeight	Double	Number of constraint weight

Parameters (selection among assigned lectures, when the solution is complete):

Related Solver Parameters

Parameter	Type	Comment
Comparator.HardStudentConflictWeight	Double	Hard student conflict weight
Comparator.StudentConflictWeight	Double	Student conflict weight
Comparator.TimePreferenceWeight	Double	Time preference weight
Comparator.ContrPreferenceWeight	Double	Group constraint preference weight
Comparator.RoomPreferenceWeight	Double	Room preference weight
Comparator.UselessSlotWeight	Double	Useless slot weight
Comparator.TooBigRoomWeight	Double	Too big room weight
Comparator.DistanceInstructorPreferenceWeight	Double	Distance (of the rooms of the back-to-back classes) based instructor preferences weight
Comparator.DeptSpreadPenaltyWeight	Double	Department balancing penalty (see DepartmentSpreadConstraint)

Parameters (selection among subset of lectures (faster)):

Related Solver Parameters

Parameter	Type	Comment
Lecture.SelectionSubSet	Boolean	Selection among subset of lectures (faster)
Lecture.SelectionSubSetMinSize	Double	Minimal subset size
Lecture.SelectionSubSetPart	Double	Subset size in percentage of all lectures available for selection

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/.

See Also:

PlacementSelection

Constructor Summary

Constructors

Constructor and Description
LectureSelection(DataProperties properties)

Method Summary

Modifier and Type	Method and Description
void	init(Solver<Lecture,Placement> solver) Initialization
Lecture	selectVariable(Solution<Lecture,Placement> solution) Variable selection

Methods inherited from class java.lang.Object

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

Constructor Detail

LectureSelection

public LectureSelection(DataProperties properties)

Method Detail

init

public void init(Solver<Lecture,Placement> solver)

Description copied from interface: VariableSelection

Initialization

Specified by:

init in interface VariableSelection<Lecture,Placement>

Parameters:

solver - current solver

selectVariable

public Lecture selectVariable(Solution<Lecture,Placement> solution)

Description copied from interface: VariableSelection

Variable selection

Specified by:

selectVariable in interface VariableSelection<Lecture,Placement>

Parameters:

solution - current solution

Returns:

selected variable